Changes

===2.1 Introduction===The contact parts are important components in switching devices. They have tomaintain their function from the new state until the end of the functional life of thedevices.

The requirements on contacts are rather broad. Besides typical contact propertiessuch as

they They have to exhibit physical, mechanical, and chemical properties like high electricaland thermal conductivity, high hardness, high corrosion resistance, etc . and besidesthis , should have good mechanical workability, and also be suitable for good weld andbrazing attachment to contact carriers. In addition they must be made fromenvironmentally friendly materials.

Materials suited for use as electrical contacts can be divided into the following groupsbased on their composition and metallurgical structure:

*'''Pure metals''' Within this group, silver has the greatest importance for switching devices in the higher energy technology. Other precious metals such as gold and platinum are only used in applications for the information technology in the form of thin surface layers. As a nonprecious metal, tungsten is used for some special applications such as, for example, automotive horn contacts. In some rarer cases, pure copper is used, but mainly paired to a silver-based contact material. '''Alloys''' Besides these few pure metals, a larger number of alloy materials made by melt technology are available for the use as contacts. An alloy is characterized by the fact, that its components are completely or partially soluble in each other in the solid state. Phase diagrams for multiple metal compositions show the number and type of the crystal structure as a function of the temperature and composition of the alloying components.

Besides these few pure metals a larger number They indicate the boundaries of liquid and solid phases and define the parameters of alloy materials made by meltsolidification.technology are available for Alloying allows to improve the use as contacts. An alloy is characterized by properties of one material at the factthat its components are completely or partially soluble in each other in cost of changing them for the solid statesecond material.Phase diagrams for multiple metal compositions show As an example, the number and type hardness of a base metal may be increased while at thecrystal structure as a function of same time the temperature and composition electrical conductivity decreases with even small additions of the second alloying componentscomponent.

*Composite Materialsmaterials are a material group whose properties are of great importance for electrical contacts that are used in switching devices for higherelectrical currents.

Composite materials are a material group whose properties are of greatimportance for electrical contacts that are used in switching devices for higherelectrical currents.Those used in electrical contacts are heterogeneous materials , composed of twoor more uniformly dispersed components , in which the largest volume portionconsists of a metal.The properties of composite materials are determined mainly independent fromeach other by the properties of their individual components. Therefore it is forexample possible to combine the high melting point and arc erosion resistanceof tungsten with the low melting and good electrical conductivity of copper, orthe high conductivity of silver with the weld resistant metalloid graphite.

Figure 2The properties of composite materials are determined mainly independent from each other by the properties of their individual components.1 Therefore it is, for example, possible to combine the high melting point and arc erosion resistance of tungsten with the low melting and good electrical conductivity of copper or the high conductivity of silver with the weld resistant metalloid graphite. <xr id="fig:Powder metallurgical manufacturing of composite materials (schematic)"/> shows the schematic manufacturing processes from powderblending to contact material. Three basic process variations are typicallyapplied:

During sintering without a liquid phase <figure id="fig:Powder metallurgical manufacturing of composite materials (left side of schematic) the powder mix is">first densified by pressing, then undergoes a heat treatment [[File:Powder metallurgical manufacturing of composite materials (sinteringschematic), andeventually is re-pressed again to further increase the density. The sinteringatmosphere depends on the material components and later application; avacuum is used for example for the low gas content material Cu/Cr. Thisprocess is used for individual contact parts and also termed pressjpg|thumb|<caption>Powder-sinterrepressmetallurgical manufacturing of composite materials (PSRschematic). For materials with high silver content T_s = Melting point of the starting point atpressing is most a larger block (or billetlower melting component) which is then after sintering hotextruded into wire, rod, or strip form. The extrusion further increases the density</caption>]]of these composite materials and contributes to higher arc erosion resistance.Materials such as Ag</Ni, Ag/MeO, and Ag/C are typically produced by thisprocess. Sintering with liquid phase has the advantage of shorter process times due tothe accelerated diffusion and also results in near-theoretical densities of thefigure>

FigDuring ''sintering without a liquid phase'' (left side of schematic), the powder mix is first densified by pressing, then undergoes a heat treatment (sintering) and eventually is re-pressed again to further increase the density. 2The sintering atmosphere depends on the material components and later application; a vacuum is used for example for the low gas content material Cu/Cr.1: PowderThis process is used for individual contact parts and also termed press-metallurgical manufacturing of composite sinter-repress (PSR). For materials with high silver content, the starting point before pressing is mostly a large block (schematicor billet)T = Melting point which is then, after sintering, hot extruded into wire, rod or strip form. The extrusion further increases the density of the lower melting componentthese composite materials and contributes to higher arc erosion resistance. Materials such as Ag/Ni, Ag/MeO and Ag/C are typically produced by this process.

''Sintering with liquid phase'' has the advantage of shorter process times due to the accelerated diffusion and also results in near-theoretical densities of the composite material. To ensure the shape stability during the sintering process , it

As opposed to the liquid phase sintering , which has limited use for electricalcontact manufacturing, the ''Infiltration process '' as shown on the right side of theschematic , has a broad practical range of applications. In this process thepowder of the higher melting component , sometimes also as a powder mix witha small amount of the second material , is pressed into parts and . Then, right after sintering, the porous skeleton is infiltrated with liquid metal of the second material. Thefilling fill-up process of the pores happens through capillary forces. This process reaches, after the infiltration , near-theoretical density without subsequent pressing and iswidely used for Ag- and Cu-refractory contacts. For Ag/W or Ag/WC contacts,controlling the amount or excess on the bottom side of the contact of theinfiltration metal Ag , results in contact tips that can be easily attached to theircarriers by resistance welding. For larger Cu/W contacts , additional machining isoften used to obtain the final shape of the contact component. ===2.2 Gold Based Materials=== Pure Gold is besides Platinum the chemically most stable of all precious metals.In its pure form it is not very suitable for use as a contact material in electromechanical devices because of its tendency to stick and cold-weld at even low contact forces. In addition it is not hard or strong enough to resistmechanical wear and exhibits high materials losses under electrical arcingloads. This limits its use in form of thin electroplated or vacuum deposited layers. For most electrical contact applications gold alloys are used. Depending on thealloying metal the melting is performed either under in a reducing atmosphere orin a vacuum. The choice of alloying metals depends on the intended use of theresulting contact material. The binary Au alloys with typically <10 wt% of otherprecious metals such as Pt, Pd, or Ag or non-precious metals like Ni, Co, andCu are the more commonly used ones (Table 2.2). On one hand these alloyadditions improve the mechanical strength and electrical switching propertiesbut on the other hand reduce the electrical conductivity and chemical corrosionresistance (Fig. 2.2) to varying degrees. Under the aspect of reducing the gold content ternary alloys with a gold contentof approximately 70 wt% and additions of Ag and Cu or Ag and Ni resp., forexample AuAg25Cu5 or AuAg20Cu10 are used which exhibit for manyapplications good mechanical stability while at the same time have sufficientresistance against the formation of corrosion layers (Table 2.3). Other ternaryalloys based on the AuAg system are AuAg26Ni3 and AuAg25Pt6. These alloysare mechanically similar to the AuAgCu alloys but have significantly higheroxidation resistance at elevated temperatures (Table 2.4). Caused by higher gold prices over the past years the development of alloys withfurther reduced gold content had a high priority. The starting point has been theAuPd system which has continuous solubility of the two components. Besidesthe binary alloy of AuPd40 and the ternary one AuPd35Ag9 other multiplecomponent alloys were developed. These alloys typically have < 50 wt% Au andoften can be solution hardened in order to obtain even higher hardness andtensile strength. They are mostly used in sliding contact applications. Gold alloys are used in the form of welded wire or profile (also called weldtapes),segments, contact rivets, and stampings produced from clad stripmaterials. The selection of the bonding process is based on the cost for thejoining process, and most importantly on the economical aspect of using theleast possible amount of the expensive precious metal component. Besides being used as switching contacts in relays and pushbuttons, goldalloys are also applied in the design of connectors as well as sliding contacts forpotentiometers, sensors, slip rings, and brushes in miniature DC motors(Table 2.5). Table 2.3: Mechanical Properties of Gold and Gold-Alloys Table 2.1: Commonly Used Grades of Gold Table 2.2: Physical Properties of Gold and Gold-Alloys Fig. 2.2:Influence of 1-10 atomic% of differentalloying metals on the electrical resistivity of gold(according to J. O. Linde) Fig. 2.3:Phase diagramof goldplatinum Fig. 2.4:Phase diagramof gold-silver Fig. 2.5:Phase diagramof gold-copper Fig. 2.6: Phase diagram of gold-nickel Fig. 2.7: Phase diagram of gold-cobalt Fig. 2.8:Strain hardeningof Au by cold working Fig. 2.9:Softening of Au after annealingfor 0.5 hrs after 80%cold working Fig. 2.10:Strain hardening ofAuPt10 by cold working Fig. 2.11:Strain hardeningof AuAg20 by cold working Fig. 2.12:Strain hardening ofAuAg30 by cold working Fig. 2.13:Strain hardening of AuNi5by cold working Fig. 2.14:Softeningof AuNi5 after annealingfor 0.5 hrs after 80%cold working Fig. 2.15:Strain hardeningof AuCo5 by cold working Fig. 2.16:Precipitation hardening ofAuCo5 at 400°C hardeningtemperature Fig. 2.17:Strain hardeningof AuAg25Pt6 by cold working Fig. 2.18:Strain hardeningof AuAg26Ni3 by cold working Fig. 2.19:Softeningof AuAg26Ni3 afterannealing for 0.5 hrsafter 80% coldworking Fig. 2.20:Strain hardening ofAuAg25Cu5by cold working Fig. 2.21:Strain hardening ofAuAg20Cu10by cold working Fig. 2.22:Softeningof AuAg20Cu10 afterannealing for 0.5 hrsafter 80% cold working Fig. 2.23:Strain hardening ofAuCu14Pt9Ag4by cold working Fig. 2.24:Precipitationhardening ofAuCu14Pt9Ag4at differenthardeningtemperaturesafter 50%cold working Table 2.4: Contact and Switching Properties of Gold and Gold Alloys Table 2.5: Application Examples and Forms of Gold and Gold Alloys ===2.3 Platinum Metal Based Materials=== The platinum group metals include the elements Pt, Pd, Rh, Ru, Ir, and Os (Table2.6). For electrical contacts platinum and palladium have practical significanceas base alloy materials and ruthenium and iridium are used as alloying components.Pt and Pd have similar corrosion resistance as gold but because of theircatalytical properties they tend to polymerize adsorbed organic vapors on contactsurfaces. During frictional movement between contact surfaces the polymerizedcompounds known as “brown powder” are formed which can lead to significantlyincrease in contact resistance. Therefore Pt and Pd are typically used as alloys andnot in their pure form for electrical contact applications. Rhodium is not used as a solid contact material but is applied for example as aelectroplated layer in sliding contact systems. Ruthenium is mostly used as an alloyingcomponent in the material PdRu15. The metals osmium and iridium have no practicalapplications in electrical contacts. Since Pd was for the longest time rather stable in price it was looked at as a substitutefor the more expensive gold. This was followed by a steep increase in the Pd pricewhich caused a significant reduction in its use in electrical contacts. Today (2011) thePd price again is lower than that of gold. Alloys of Pt with Ru, Ir, Ni, and W were widely used in electromechanical componentsin the telecommunication industry and in heavy duty automotive breaker points (Table2.7). Today these components have been replaced in many applications by solidstate technology and the usage of these materials is greatly reduced. Pd alloyshowever have a more significant importance. PdCu15 is widely used for example inautomotive flasher relays. Because of their resistance to sulfide formation PdAg alloysare applied in various relay designs. The ability to thermally precipitation harden somemulti component alloys based on PdAgAuPt they find special usage in wear resistantsliding contact applications. Pd44Ag38Cu15PtAuZn is a standard alloy in this group. Platinum and palladium alloys are mainly used similar to the gold based materials inthe form of welded wire and profile segments but rarely as contact rivets. Because ofthe high precious metal prices joining technologies are used that allow the mosteconomic application of the contact alloy in the area where functionally needed.Because of their resistance to material transfer they are used for DC applications anddue to their higher arc erosion resistance they are applied for medium electrical loadsup to about 30W in relays and switches (Table 2.10). Multi-component alloys basedon Pd with higher hardness and wear resistance are mainly used as spring arms insliding contact systems and DC miniature motors. Table 2.6: Properties, Production Processes, and Application Forms for Platinum Metals Table 2.7: Physical Properties of the Platinum Metals and their Alloys Table 2.8: Mechanical Properties of the Platinum Metals and their Alloys Fig. 2.25:Influence of 1-20 atom% ofdifferent additivemetals on theelectricalresistivity p ofplatinum(Degussa) Fig. 2.26:Influence of 1-22 atom% of differentadditive metals on the electricalresistivityp of palladium Fig. 2.27:Phase diagram ofplatinum-iridium Fig. 2.28:Phase diagram ofplatinum-nickel Fig. 2.29:Phase diagramof platinum-tungsten Fig. 2.30:Phase diagram ofpalladium-copper Fig. 2.31:Strainhardeningof Pt by coldworking Fig. 2.32:Softening of Pt afterannealing for 0.5 hrsafter 80%cold working Fig. 2.33:Strain hardening of PtIr5by cold working Fig. 2.34:Softening of PtIr5 after annealing for 1 hrafter different degrees of cold working Fig. 2.35:Strain hardeningof PtNi8 by cold working Fig. 2.36:Softening of PtNi8 afterannealingfor 1 hr after80% cold working Fig. 2.37:Strain hardeningof PtW5 by cold working Fig. 2.38:Softeningof PtW5 afterannealing for 1hrafter 80% coldworking Fig. 2.39:Strain hardeningof Pd 99.99 by cold working Fig. 2.40:Strain hardeningof PdCu15 by cold working Fig. 2.41:Softeningof PdCu15 afterannealingfor 0.5 hrs Fig. 2.42:Strain hardeningof PdCu40 by cold working Fig. 2.43:Softeningof PdCu40after annealingfor 0.5 hrs after 80%cold working Fig. 2.44:Electrical resistivity pof PdCu alloys with and without anannealing step for forming an orderedphase Table 2.9: Contact and Switching Propertiesof the Platinum Metals and their Alloys Table 2.10: Application Examples and Formof Supply for Platinum Metals and their Alloys ===2.4 Silver Based Materials=== ===2.4.1 Pure Silver===Pure silver (also called fine silver) exhibits the highest electrical and thermalconductivity of all metals. It is also resistant against oxidation. Major disadvantagesare its low mechanical wear resistance, the low softening temperature,and especially its strong affinity to sulfur and sulfur compounds. In the presenceof sulfur and sulfur containing compounds brownish to black silver sulfide layerare formed on its surface. These can cause increased contact resistance oreven total failure of a switching device if they are not mechanically, electrically,or thermally destroyed. Other weaknesses of silver contacts are the tendency toweld under the influence of over-currents and the low resistance againstmaterial transfer when switching DC loads. In humid environments and underthe influence of an electrical field silver can creep (silver migration) and causeelectrical shorting between adjacent current paths. Table 2.11 shows the typically available quality grades of silver. In certaineconomic areas, i.e. China, there are additional grades with varying amounts ofimpurities available on the market. In powder form silver is used for a widevariety of silver based composite contact materials. Different manufacturingprocesses result in different grades of Ag powder as shown in Table 2.12.additional properties of silver powders and their usage are describedin chapter 8.1.Semi-finished silver materials can easily be warm or cold formed and can beclad to the usual base materials. For attachment of silver to contact carriermaterials welding of wire or profile cut-offs and brazing are most widely applied.Besides these mechanical processes such as wire insertion (wire staking) andthe riveting (staking) of solid or composite contact rivets are used in themanufacture of contact components. Contacts made from fine silver are applied in various electrical switchingdevices such as relays, pushbuttons, appliance and control switches forcurrents < 2 A (Table 2.16). Electroplated silver coatings are widely used toreduce the contact resistance and improve the brazing behavior of other contactmaterials and components. Table 2.11: Overview of the Most Widely Used Silver Grades Table 2.12: Quality Criteria of Differently Manufactured Silver Powders Fig. 2.45:Strain hardeningof Ag 99.95 by cold working Fig. 2.46:Softening of Ag 99.95after annealing for 1 hr after differentdegrees of strain hardening

==Gold Based Materials=2.4.2 Silver Alloys===To improve the physical and contact properties of fine silver melt-metallurgicalproduced silver alloys are used (Table 2.13). By adding metal components themechanical properties such as hardness and tensile strength as well as typicalcontact properties such as erosion resistance, and resistance against materialtransfer in DC circuits are increased (Table 2.14). On the other hand however,other properties such as electrical conductivity and chemical corrosionresistance can be negatively impacted by alloying (Figs. 2.47 and 2.48).

===2Pure Gold is besides Platinum the chemically most stable of all precious metals.4.2.1 Fine-Grain Silver===Fine-Grain Silver (ARGODUR-Spezial) In its pure form, it is defined not very suitable for use as a silver alloy with an additioncontact material in electromechanical devices because of 0.15 wt% of Nickel. Silver its tendency to stick and nickel are not soluble in each other in solidformcold-weld at even low contact forces. In liquid silver only a small amount of nickel addition, it is soluble as the phase diagram(Fignot hard or strong enough to resist mechanical wear and exhibits high material losses under electrical arcing loads. 2.51) illustrates. During solidification of the melt this nickel addition getsfinely dispersed This limits its use in the silver matrix and eliminates the pronounce coarse graingrowth after prolonged influence form of elevated temperatures (Figs. 2.49 and 2.50thin electroplated or vacuum deposited layers.

==Platinum Metal Based Materials=2.4.2.2 Hard-Silver Alloys===Using copper as an alloying component increases the mechanical stability ofsilver significantly. The most important among the binary AgCu alloys is that ofAgCu3, known in europe also under the name of hard-silver. This material stillhas a chemical corrosion resistance close to that of fine silver. In comparison topure silver and fine-grain silver AgCu3 exhibits increased mechanical strengthas well as higher arc erosion resistance and mechanical wear resistance(Table 2.14).

Increasing The platinum group metals include the Cu content further also increases the mechanical strength ofAgCu alloys elements Pt, Pd, Rh, Ru, Ir and Os ([[Platinum_Metal_Based_Materials|Table 1]]<!--(Table 2.6)-->). For electrical contacts, platinum and palladium have practical significance as base alloy materials and ruthenium and improves arc erosion resistance iridium are used as alloying components. Pt and Pd have similar corrosion resistance againstmaterial transfer while at as gold but due to their catalytical properties, they tend to polymerize adsorbed organic vapors on contact surfaces. During frictional movement between contact surfaces, the same time however the tendency polymerized compounds known as “brown powder” are formed, which can lead to oxide formationbecomes detrimental. This causes during switching under arcing conditions ana significant increase in contact resistance with rising numbers of operation. In specialapplications where highest mechanical strength is recommended Therefore Pt and a reducedchemical resistance can be tolerated, the eutectic AgCu alloy with 28 wt% ofcopper (Fig. 2.52) is Pd are typically used. AgCu10 also known as coin silver has beenreplaced in many applications by composite silver-based materials while sterlingsilver (AgCu7.5) has never extended its important usage from decorative tablewear alloys and jewelry to industrial applications are rather not used in their pure form for electrical contactscontact applications.

Dispersion hardened alloys of silver with 0.5 wt% MgO ==Tungsten and NiO (ARGODUR 32)are produced by internal oxidation. While the melt-metallurgical alloy is easy tocold-work and form the material becomes very hard and brittle after dispersionhardening. Compared to fine silver and hard-silver this material has a greatlyimproved temperature stability and can be exposed to brazing temperatures upto 800°C without decreasing its hardness and tensile strength.Because of these mechanical properties and its high electrical conductivityMolybdenum Based Materials==

Table 2.13Main Article: Physical Properties of Silver [[Tungsten and Silver AlloysMolybdenum Based Materials| Tungsten and Molybdenum Based Materials]]

ARGODUR 32 is mainly used in the form of contact springs that are exposed tohigh thermal and mechanical stresses in relays, and contactors ==Contact Materials for aeronauticapplications.Vacuum Switches==

FigThe low gas content contact materials are developed for the use in vacuum switching devices. 2.47:Influence of 1-10 atom% of differentalloying metals on the electrical resistivity ofsilver

Fig. 2.48Main Article:Electrical resistivity pof AgCu alloys with 0-20 weight% Cuin the soft annealedand tempered stagea) Annealed and quenchedb) Tempered at 280°C[[Contact Materials for Vacuum Switches| Contact Materials for Vacuum Switches]]

FigVinaricky, E. 2(Hrsg.50): Fine grain microstructureElektrische Kontakte, Werkstoffe und Anwendungen.of AgNi0Springer-Verlag, Berlin, Heidelberg etc.15 after 80% cold workingand 1 hr annealing at 600°C2002

FigLindmayer, M. 2: Schaltgeräte-Grundlagen, Aufbau, Wirkungsweise.51:Phase diagramof silverSpringer-nickelVerlag, Berlin, Heidelberg, New York, Tokio, 1987

FigRau, G. 2: Metallische Verbundwerkstoffe.52:Phase diagramWerkstofftechnischeof silver-copperVerlagsgesellschaft, Karlsruhe 1977

FigSchreiner, H. 2: Pulvermetallurgie elektrischer Kontakte.53:Springer-VerlagPhase diagram ofsilver-cadmiumBerlin, Göttingen, Heidelberg, 1964

Table 2Hansen. M.; Anderko, K.14: Mechanical Properties Constitution of Silver and Silver Binary Alloys. New York:Mc Graw-Hill, 1958

FigShunk, F. 2A.54:Strain hardeningConstitution of AgCu3by cold workingBinary Alloy. 2 Suppl. New York; Mc Graw-Hill, 1969

FigEdelmetall-Taschenbuch. 2( Herausgeber Degussa AG, Frankfurt a.55:Softening of AgCu3after annealing for 1 hrM.),after 80% cold workingHeidelberg, Hüthig-Verlag, 1995

FigRau, G. 2: Elektrische Kontakte-Werkstoffe und Technologie.56:Eigenverlag G. RauStrain hardening of AgCu5 by coldworkingGmbH & Co., Pforzheim, 1984

FigHeraeus, W. 2C.57:Softening of AgCu5 afterannealing for 1 hr after 80% coldworkingWerkstoffdaten. Eigenverlag W.C. Heraeus, Hanau, 1978

FigLinde, J. 2O.58:Elektrische Widerstandseigenschaften der verdünnten LegierungenStrain hardening of AgCu 10by cold workingdes Kupfers, Silbers und Goldes. Lund: Hakan Ohlsson, 1938

FigGroßmann, H. 2Saeger, K. E.; Vinaricky, E.60:Gold and Gold Alloys in ElectricalStrain hardening of AgCu28 byEngineering. in: Gold, Progress in Chemistry, Biochemistry and Technology. Johncold workingWiley & Sons, Chichester etc, (1999) 199-236

FigGehlert, B. 2: Edelmetall-Legierungen für elektrische Kontakte.Metall 61:Softening of AgCu28after annealing for 1 hr after80% cold working(2007) H. 6, 374-379

FigAldinger, F. 2; Schnabl, R.62:Strain hardening of AgNi0Edelmetallarme Kontakte für kleine Ströme.15by cold workingMetall 37 (1983) 23-29

FigBischoff, A. 2; Aldinger, F.63:Einfluss geringer Zusätze auf die mechanischenSoftening of AgNi0Eigenschaften von Au-Ag-Pd-Legierungen.15after annealing for 1 hr after 80%cold workingMetall 36 (1982) 752-765

FigWise, E. 2M.64: Palladium, Recovery, Properties and Uses. New York, London:Strain hardening ofARGODUR 27by cold workingAcademic Press 1968

FigSavitskii, E. 2M.; Polyakova, V.P.; Tylina, M.A.65:Palladium Alloys, Primary Sources.Softeningof ARGODUR 27 after annealingfor 1 hr after 80% cold workingNew York: Publishers 1969

Table 2Gehlert, B.15: Contact and Switching Properties of Silver and Silver AlloysLebensdaueruntersuchungen von Edelmetall Kontaktwerkstoff-Kombinationen für Schleifringübertrager. VDE-Fachbericht 61, (2005) 95-100

Table 2Holzapfel,C.16: Application Examples and Forms of Supply for Silver and Silver AlloysVerschweiß und elektrische Eigenschaften vonSchleifringübertragern. VDE-Fachbericht 67 (2011) 111-120

===2Schnabl, R.4; Gehlert, B.2.3 Silver: Lebensdauerprüfungen von Edelmetall-Palladium Alloys===The addition of 30 wt% Pd increases the mechanical properties as well as theresistance of silver against the influence of sulfur and sulfur containingSchleifkontaktwerkstoffen für Gleichstrom Kleinmotoren.compounds significantly Feinwerktechnik & Messtechnik (Tables 2.17 and 2.181984).Alloys with 408, 389-60 wt% Pd have an even higher resistance against silver sulfideformation. At these percentage ranges however the catalytic properties ofpalladium can influence the contact resistance behavior negatively. Theformability also decreases with increasing Pd contents.393

AgPd alloys are hardKobayashi, arc erosion resistantT.; Koibuchi, and have a lower tendency towardsmaterial transfer under DC loads (Table 2K.; Sawa, K.19); Endo, K. On the other hand the electricalconductivity is decreased at higher Pd contents; Hagino, H. The ternary alloy AgPd30Cu5: A Study of Lifetimehas an even higher hardness which makes it suitable of Au-plated Slip-Ring and AgPd Brush System for use in sliding contactPower Supply.systemsth Proc.24 Int. Conf. on Electr. Contacts, Saint Malo, France 2008, 537-542

AgPd alloys are mostly used in relays for the switching of medium to higher loads(>60VHarmsen, >2A) as shown in Table 2U.20. Because of the high palladium price theseformerly solid contacts have been widely replaced by multi-layer designs suchas AgNi0; Saeger K.15 or AgNi10 with a thin Au surface layerE. A broader field of application: Über das Entfestigungsverhalten von Silberfor AgPd alloys remains in the wear resistant sliding contact systemsverschiedener Reinheiten.Metall 28 (1974) 683-686

FigBehrens, V. 2; Michal, R.; Minkenberg, J.N.; Saeger, K.E.66: Phase diagram of silverAbbrand undKontaktwiderstandsverhalten von Kontaktwerkstoffen auf Basis von Silber-Nickel. e.& i. 107. Jg. (1990), 2, 72-palladium77

FigBehrens, V. 2.67:Silber/Nickel und Silber/Grafit- zwei Spezialisten auf dem GebietStrain hardeningof AgPd30 by cold workingder Kontaktwerkstoffe. Metall 61 (2007) H.6, 380-384

FigRieder, W. 2.68:Silber / Metalloxyd-Werkstoffe für elektrische Kontakte,Strain hardeningof AgPd50 by cold workingVDE - Fachbericht 42 (1991) 65-81

FigHarmsen,U. 2.69:Die innere Oxidation von AgCd-Legierungen unterStrain hardeningSauerstoffdruck.of AgPd30Cu5by cold workingMetall 25 (1991), H.2, 133-137

FigMuravjeva, E.M.; Povoloskaja, M. 2D.70:Verbundwerkstoffe Silber-Zinkoxid undSoftening of AgPd30Silber-Zinnoxid, AgPd50,and AgPd30Cu5 after annealing of 1 hrhergestellt durch Oxidationsglühen.after 80% cold workingElektrotechnika 3 (1965) 37-39

Table Behrens, V.; Honig Th.; Kraus, A.; Michal, R.; Saeger, K.-E.; Schmidberger, R.;Staneff, Th.: Eine neue Generation von AgSnO₂ -Kontaktwerkstoffen.17: Physical Properties of SilverVDE-Fachbericht 44, (1993) 99-Palladium Alloys114

Table 2Braumann, P.; Lang, J.18: Mechanical Properties of SilverKontaktverhalten von Ag-Metalloxiden für den Bereichhoher Ströme. VDE-Fachbericht 42, (1991) 89-Palladium Alloys94

Table Hauner, F.; Jeannot, D.; Mc Neilly, U.; Pinard, J.: Advanced AgSnO Contact 2th Materials for High Current Contactors. Proc. 20 Int. Conf. on Electr.19: Contact and Switching Properties of SilverPhenom., Stockholm 2000, 193-Palladium Alloys198

Table 2Wintz, J.-L.; Hardy, S.; Bourda, C.20: Application Examples Influence on the Electrical Performances ofAssembly Process, Supports Materials and Forms of Suppl Production Means for SilverAgSnO₂ .Proc.24_th Int. Conf. on Electr. Contacts, Saint Malo, France 2008, 75-Palladium Alloys81

===2Behrens, V.4; Honig, Th.3 Silver Composite Materials===; Kraus, A.; Michal, R.: Schalteigenschaften vonverschiedenen Silber-Zinnoxidwerkstoffen in Kfz-Relais. VDE-Fachbericht 51(1997) 51-57

===2Schöpf, Th.4.3.1 Silver: Silber/Zinnoxid und andere Silber-Nickel (SINIDUR) Materials===Since silver and nickel are not soluble in each other in solid form and Metalloxidwerkstoffe in the liquidphase have only very limited solubility silver nickel composite materials withhigher Ni contents can only be produced by powder metallurgyNetzrelais. During extrusionof sintered Ag/Ni billets into wires, strips and rods the Ni particles embedded inthe Ag matrix are stretched and oriented in the microstructure into a pronouncedfiber structure VDE-Fachbericht 51 (Figs. 2.75. and 2.761997)41-50

The high density produced during hot extrusion aids the arc erosion resistanceof these materials (Tables 2Schöpf, Th.; Behrens, V.21 and 2; Honig, Th.22); Kraus, A. The typical application : Development of Ag/NiSilver Zinccontact materials is in devices th Oxide for switching currents of up to 100A (Table 2General-Purpose Relays.24).In this range they are significantly more erosion resistant than silver or silveralloysProc. In addition they exhibit with nickel contents <20 wt% a low and over theiroperational lifetime consistent contact resistance and good arc movingpropertiesInt. In DC applications Ag/Ni materials exhibit a relatively low tendencyof material transfer distributed evenly over the contact surfaces (Table 2Conf.23)on Electr.Contacts,Stockholm 2000, 187-192

Typically Ag/Ni (SINIDUR) materials are usually produced with contents of 10-40wt% NiBraumann, P. The most widely used materials SINIDUR 10 and SINIDUR 20- and alsoSINIDUR 15; Koffler, mostly used in north america-A.: Einfluss von Herstellverfahren, are easily formable and applied byMetalloxidgehalt undcladding (FigsWirkzusätzen auf das Schaltverhalten von Ag/SnO in Relais. 2.71VDE-2.74). They can be, without any additional welding aidsFachbericht 59,economically welded and brazed to the commonly used contact carriermaterials.The (SINIDUR2003) materials with nickel contents of 30 and 40 wt% are used inswitching devices requiring a higher arc erosion resistance and where increasesin contact resistance can be compensated through higher contact forces.133-142

The most important applications for Ag/Ni contact materials are typically inrelaysKempf, wiring devicesB.; Braumann, appliance switchesP.; Böhm, thermostatic controlsC.; Fischer-Bühner, auxiliaryJ.: Silber-Zinnoxid-switches, and small contactors with nominal currents >20A Werkstoffe: Herstellverfahren und Eigenschaften. Metall 61(Table 2.242007)H.6, 404-408

Table 2Lutz, O.; Behrens, V.; Finkbeiner, M.; Honig, T.; Späth, D.21: Physical Properties of SilverAg/CdO-Nickel Ersatz inLichtschaltern. VDE-Fachbericht 61, (SINIDUR2005) Materials165-173

Table 2Lutz, O.; Behrens, V.; Wasserbäch, W.; Franz, S.; Honig, Th.; Späth,D.; Heinrich, J.22: Mechanical Properties of Improved Silver/Tin Oxide Contact Materials for Automotiveth Applications. Proc.24 Int. Conf. on Electr. Contacts, Saint Malo, France 2008,88-Nickel (SINIDUR) Materials93

FigLeung, C. 2; Behrens, V.71:Strain hardeningA Review of Ag/Ni 90/10 by cold workingSnO Contact Materials and Arc Erosion. 2th Proc.24 Int. Conf. on Electr. Contacts, Saint Malo, France 2008, 82-87

FigChen, Z. 2K.; Witter, G.J.72:Comparison in Performance for Silver–Tin–IndiumSoftening of Ag/Ni 90/10Oxide Materials Made by Internal Oxidation and Powder Metallurgy.after annealingth Proc. 55 IEEE Holm Conf. on Electrical Contacts, Vancouver, BC, Canada,for 1 hr after 80% cold working(2009) 167 – 176

FigRoehberg, J. 2; Honig, Th.; Witulski, N.; Finkbeiner, M.; Behrens, V.73:Strain hardeningPerformanceof AgDifferent Silver/Ni 80/20 by cold workingTin Oxide Contact Materials for Applications in Low Voltageth Circuit Breakers. Proc. 55 IEEE Holm Conf. on Electrical Contacts, Vancouver,BC, Canada, (2009) 187 – 194

FigMuetzel, T. 2; Braumann, P.; Niederreuther, R.74:Temperature Rise Behavior ofSoftening of th Ag/Ni 80/20SnO Contact Materials for Contactor Applications. Proc. 55 IEEE Holm 2after annealingfor 1 hr after 80% cold workingConf. on Electrical Contacts, Vancouver, BC, Canada, (2009) 200 – 205

FigLutz, O. 2et al.75: Micro structure of AgSilber/Ni 90/10 a) perpendicular to the extrusion directionZinnoxid – Kontaktwerkstoffe auf Basis der InnerenOxidation fuer AC – und DC – Anwendungen.bVDE Fachbericht 65 (2009) parallel to the extrusion direction167 – 176

FigHarmsen, U. 2; Meyer, C.L.76: Micro structure of Ag/Ni 80/20 a) perpendicular to the extrusion directionMechanische Eigenschaften stranggepresster Silber-bGraphit-Verbundwerkstoffe. Metall 21 (1967) parallel t o the extrusion direction, 731-733

Table 2Behrens, V.23: Mahle, E.; Michal, R.; Saeger, K.E.: An Advanced Silver/Graphiteth Contact and Switching Properties of SilverMaterial Based on Graphite Fibre. Proc. 16 Int. Conf. on Electr.Contacts, Loghborough 1992, 185-Nickel (SINIDUR) Materials189

Table 2Schröder, K.-H.; Schulz, E.-D.24: Application Examples and Forms of SupplyÜber den Einfluss des Herstellungsverfahrensfor Silverth auf das Schaltverhalten von Kontaktwerkstoffen der Energietechnik. Proc. 7 Int.Conf. on Electr. Contacts, Paris 1974, 38-Nickel (SINIDUR) Materials45

===2Mützel, T.4.3.2: Silver-Metal Oxide Materials Ag/CdONiederreuther, Ag/SnO , Ag/ZnO===The family of silver-metal oxide contact materials includes the material groupsR.:Kontaktwerkstoffe für Hochleistungsanwendungen.silverVDE-cadmium oxide Bericht 67 (DODURIT CdO2011), silver-tin oxide (SISTADOX), and silverzincoxide (DODURIT ZnO). Because of their very good contact and switchingproperties like high resistance against welding, low contact resistance, and higharc erosion resistance, silver103-metal oxides have gained an outstanding positionin a broad field of applications. They mainly are used in low voltage electricalswitching devices like relays, installation and distribution switches, appliances,industrial controls, motor controls, and protective devices (Table 2.13).110

*Lambert, C.; Cambon, G.: The Influence of Manufacturing Conditions andMetalurgical Characteristics on the Electrical Behaviour of Silver-cadmium oxide (DODURIT CdO) materialsGraphiteth Contact Materials. Proc. 9 Int. Conf.on Electr. Contacts,Chicago 1978, 401-406

SilverVinaricky, E.: Grundsätzliche Untersuchungen zum Abbrand- undSchweißverhalten von Ag/C-cadmium oxide Kontaktwerkstoffen. VDE-Fachbericht 47 (DODURIT CdO1995) materials with 10159-15 wt% are producedby both, internal oxidation and powder metallurgical methods (Table 2.25).169

The manufacturing of strips and wires by internal oxidation starts with a moltenalloy of silver and cadmiumAgte, C. During a heat treatment below it's melting point in aoxygen rich atmosphere in such a homogeneous alloy the oxygen diffuses fromthe surface into the bulk of the material and oxidizes the Cd to CdO in a more orless fine particle precipitation inside the Ag matrix; Vacek, J. The CdO particles are ratherfine in the surface area and are becoming larger further away towards the centerof the material (Fig. 2.83): Wolfram und Molybdän.Berlin: Akademie-Verlag 1959

During the manufacturing of Ag/CdO contact material by internal oxidation theprocesses vary depending on the type of semi-finished materialKeil, A.For Ag/CdO wires a complete oxidation of the AgCd wire is performed; Meyer, followedby wireC.-drawing to the required diameter (Figs. 2.77 and 2.78). The resultingmaterial is used for example in the production of contact rivetsL. For Ag/CdO stripmaterials two processes are commonly used: Cladding of an AgCd alloy stripwith fine silver followed by complete oxidation results in a strip material with aDer Einfluß des Faserverlaufes auf die elektrischesmall depletion area in the center of it's thickness and a Ag backing suitable foreasy attachment by brazing (sometimes called “Conventional Ag/CdO”). Usinga technology that allows the partial oxidation of a dualVerschleißfestigkeit von Wolfram-strip AgCd alloy materialin a higher pressure pure oxygen atmosphere yields a composite Ag/CdO stripmaterial that has besides a relatively fine CdO precipitation also a easily brazableAgCd alloy backing (FigKontakten. 2.85). These materials ETZ 72, (DODURIT CdO ZH1951) are mainlyused as the basis for contact profiles and contact tips.343-346

During powder metallurgical production the powder mixed made by differentprocesses are typically converted by pressingSlade, sintering and extrusion to wiresand stripsP. G. The high degree of deformation during hot extrusion produces auniform and fine dispersion of CdO particles in the Ag matrix while at the sametime achieving a high density which is advantageous : Electric Contacts for good contact properties(FigPower Interruption. A Review. 2Proc.84)19 Int. To obtain a backing suitable for brazing, a fine silver layer is appliedby either com-pound extrusion or hot cladding prior to or right after the extrusion(FigConf. 2on Electric Contact Phenom.86Nuremberg (Germany).1998, 239-245

For larger contact tipsSlade, and especially those with a rounded shape, the single tipPress-Sinter-Repress process (PSR) offers economical advantagesP. G. Thepowder mix is pressed : Variations in a die close to the final desired shape, the “green” tipsContact Resistance Resulting from Oxide Formationare sintered, and Decomposition in most cases the repress process forms the final exact shapeAgW and Ag-WC-C Contacts Passing Steady Currentswhile at the same time increasing the contact density for Long Time Periods. IEEE Trans. Components, Hybrids and hardnessManuf. Technol.CHMT-9,1 (1986) 3-16

Using different silver powders Slade, P. G.: Effect of the Electric Arc and minor additives for the basic Ag Ambient Air on the ContactResistance of Silver, Tungsten and CdOSilver-Tungsten Contacts.starting materials can help influence certain contact properties for specializedapplicationsJ.Appl.Phys.47, 8 (1976) 3438-3443

FigLindmayer, M. 2; Roth, M.77:Strain hardening Contact Resistance and Arc-Erosion of internally oxidizedW-Ag andWC-Ag/CdO 90/10 by cold working. IEEE Trans components, Hybrids and Manuf. Technol.CHMT-2, 1 (1979) 70-75

FigLeung, C. 2-H.; Kim, H.J.78:Softening A Comparison of internally oxidizedAg/CdO 90W, Ag/WC and Ag/10 after annealingMo Electricalfor Contacts. IEEE Trans. Components, Hybrids, Manuf. Technol.,Vol. CHMT-7, 1 hr after 40% cold working(1984) 69-75

Table 2Allen, S.E.; Streicher, E.25: Physical and Mechanical Properties as well as Manufacturing Processes andThe Effect of Microstructure on the ElectricalForms th Performance of Supply of Extruded Silver Cadmium OxideAg-WC-C Contact Materials. Proc. 44 IEEE Holm Conf. on Electr.Contacts, Arlington, VA, USA (DODURIT CdO1998) Contact Materials, 276-285

FigHaufe, W. 2; Reichel, W.; Schreiner H.79:Abbrand verschiedener W/Cu-Sinter-Strain hardening ofAg/CdO 90/10 P by cold workingTränkwerkstoffe an Luft bei hohen Strömen. Z. Metallkd. 63 (1972) 651-654

FigAlthaus, B. 2; Vinaricky, E.80: SofteningDas Abbrandverhalten verschieden hergestellterof Ag/CdO 90/10 P after annealingWolfram-Kupfer-Verbundwerkstoffe im Hochstromlichtbogen.for 1 hr after 40% cold workingMetall 22 (1968) 697-701

FigGessinger, G. 2H.; Melton, K.N.81:Burn-off Behaviour of WCu Contact Materials in anStrain hardeningof Ag/CdO 88/12 WPElectric Arc. Powder Metall. Int. 9 (1977) 67-72

FigMagnusson, M. 2.82:Abbrandverhalten und Rißbildung bei WCu-TränkwerkstoffenSoftening of Ag/CdO 88/12WP after annealingfor 1 hr after different degrees ofcold workingunterschiedlicher Wolframteilchengröße. ETZ-A 98 (1977) 681-683

FigHeitzinger, F. 2; Kippenberg, H.; Saeger, K.E.; Schröder, K.H.83: Micro structure of Ag/CdO 90/10 iContact Materials forVacuum Switching Devices.oProc. a) close to surfaceb) in center areaXVth ISDEIV, Darmstadt 1992, 273-278

FigGrill, R. 2; Müller, F.84: Micro structure of Ag/CdO 90/10 P:Verbundwerkstoffe auf Wolframbasis füraHochspannungsschaltgeräte. Metall 61 (2007) perpendicular to extrusion directionb) parallel to extrusion directionH. 6, 390-393

FigSlade, P. 2: G.85:The Vacuum Interrupter- Theory; Design; and Application. CRCMicro structure of Ag/CdO 90/10 ZH:1) Ag/CdO layer2Press, Boca Raton, FL (USA) AgCd backing layer, 2008

FigFrey, P. 2; Klink, N.; Saeger, K.E.86: Micro structure of AgCdO 88/12 WP: a) perpendicular to extrusion directionUntersuchungen zum Abreißstromverhalten vonbKontaktwerkstoffen für Vakuumschütze. Metall 38 (1984) parallel to extrusion direction647-651

*Silver–tin oxide(SISTADOX)materialsOver the past yearsFrey, P.; Klink, many Ag/CdO contact materials have been replaced byAg/SnO based materials with 2-14 wt% SnO 2 2 because of the toxicity ofCadmiumN. This changeover was further favored by the fact that Ag/SnO2contacts quite often show improved contact and switching properties such aslower arc erosion; Michal, higher weld resistanceR.; Saeger, and a significant lower tendencytowards material transfer in DC switching circuits (Table 2K.30)E. Ag/SnO2: Metallurgical Aspects of Contactmaterials have been optimized Materials for a broad range of applications by other metaloxide additives and modification in the manufacturing processes that result indifferent metallurgicalVacuum Switching Devices. IEEE Trans. Plasma Sc. 17, physical and electrical properties (Table 2.291989).743-740

Manufacturing of Ag/SnO2 by ''internal oxidation'' is possible in principle, butduring heat treatment of alloys containing > 5 wt% of tin in oxygenSlade, dense oxidelayers formed on the surface of the material prohibit the further diffusion ofoxygen into the bulk of the materialP. By adding Indium or Bismuth to the alloy theinternal oxidation is possible and results : Advances in materials that typically are rather hardand brittle and may show somewhat elevated contact resistance and is limitedMaterial Development for High Power Vacuum Interrupterto applications in relaysth Contacts. To make a ductile material with fine oxide dispersion(SISTADOX TOS F) (FigProc. 216 Int.114) it is necessary to use special process variationsin oxidation and extrusion which lead to materials with improved properties inrelaysConf. Adding a brazable fine silver layer to such materials results in a semifinishedmaterial suitable for the manufacture as smaller weld profiles(SISTADOX WTOS F) (Figon Electr. 2Contact Phenom.116). Because of their resistance to material,transfer and low arc erosion these materials find for example a broaderapplication in automotive relays (Table 2.31).Loughborough 1992,1-10

''Powder metallurgy'' plays a significant role in the manufacturing of Ag/SnO2contact materialsBehrens, V.; Honig, Th. Besides SnO2 a smaller amount (<1 wt%) of one or moreother metal oxides such as WO3; Kraus, MoO3A.; Allen, CuO and/or Bi2O3 are addedS. Theseadditives improve the wettability : Comparison of the oxide particles and increase the viscosityDifferent Contactof the Ag meltth Materials for Low Voltage Vacuum Applications. Proc.19 Int. Conf. on Electr. They also provide additional benefits to the mechanical andarcing contact properties of materials in this group ''(Table 2.26)''Contact Phenom., Nuremberg 1998, 247-251

In the manufacture the initial powder mixes different processes are appliedwhich provide specific advantages of the resulting materials in respect to theircontact properties ''(FigsRolle, S. 2; Lietz, A.87 – 2; Amft, D.119)''; Hauner, F. Some of them are described here asfollows:CuCr Contact Material for Low Voltage:'''a) Powder blending from single component powders''' <br> In this common process all components including additives that are part of the powder mix are blended as single powdersth Vacuum Contactors. Proc. 20 int. Conf. on Electr. Contact. The blending is usually performed in the dry stage in blenders of different designPhenom.Stockholm2000, 179-186

Kippenberg, H.:'''b) Powder blending on the basis of doped powders''' <br> For incorporation of additive oxides in the SnO2 powder the reactive spray process (RSV) has shown advantagesCrCu as a Contact Material for Vacuum Interrupters.th Proc. This process starts with a waterbased solution of the tin and other metal compounds13 Int. This solution is nebulized under high pressure and temperature in a reactor chamberConf. Through the rapid evaporation of the water each small droplet is converted into a salt crystal and from there by oxidation into a tin oxide particle in which the additive metals are distributed evenly as oxideson Electr. The so created doped AgSnO2 powder is then mechanically mixed with silver powderContact Phenom.Lausanne 1986, 140-144

Hauner, F.; Müller, R.; Tiefel, R.:'''cCuCr für Vakuumschaltgeräte-Herstellungsverfahren, Eigenschaften und Anwendung.Metall 61 (2007) Powder blending based on coated oxide powders''' <br> In this process tin oxide powder is blended with lower meting additive oxides such as for example Ag2 MoO4 and then heat treated. The SnO2 particles are coated in this step with a thin layer of the additive oxideH.6, 385-389

:'''dManufacturing Equipment for Semi-Finished Materials(Bild) Powder blending based on internally oxidized alloy powders''' <br> A combination of powder metallurgy and internal oxidation this process starts with atomized Ag alloy powder which is subsequently oxidized in pure oxygen. During this process the Sn and other metal components are transformed to metal oxide and precipitated inside the silver matrix of each powder particle.

[[de:'''e) Powder blending based on chemically precipitated compound powders''' <br> A silver salt solution is added to a suspension of for example SnO2 together with a precipitation agent. In a chemical reaction silver and silver oxide respectively are precipitated around the additive metal oxide particles who act as crystallization sites. Further chemical treatment then reduces the silver oxide with the resulting precipitated powder being a mix of Ag and SnO2.Kontaktwerkstoffe_für_die_Elektrotechnik]]