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

===2.4.2 Silver Alloys===To improve Pure Gold is besides Platinum the physical and contact properties chemically most stable of fine silver melt-metallurgicalproduced silver alloys are used (Table 2all precious metals.13). By adding metal components themechanical properties such In its pure form, it is not very suitable for use as hardness a contact material in electromechanical devices because of its tendency to stick and tensile strength as well as typicalcold-weld at even low contact properties such as erosion resistanceforces. In addition, it is not hard or strong enough to resist mechanical wear and resistance against exhibits high materialtransfer in DC circuits are increased (Table 2.14). On the other hand however,other properties such as losses under electrical conductivity and chemical corrosionresistance can be negatively impacted by alloying (Figsarcing loads. 2.47 and 2.48)This limits its use in form of thin electroplated or vacuum deposited layers.

===The platinum group metals include the elements Pt, Pd, Rh, Ru, Ir and Os ([[Platinum_Metal_Based_Materials|Table 1]]<!--(Table 2.46)-->).2For electrical contacts, platinum and palladium have practical significance as base alloy materials and ruthenium and iridium are used as alloying components.2 Hard-Silver Alloys===Using copper Pt and Pd have similar corrosion resistance as an alloying component increases the mechanical stability ofsilver significantlygold but due to their catalytical properties, they tend to polymerize adsorbed organic vapors on contact surfaces. The most important among During frictional movement between contact surfaces, the binary AgCu alloys is that ofAgCu3polymerized compounds known as “brown powder” are formed, known which can lead to a significant increase in europe also under the name of hard-silver. This material stillhas a chemical corrosion contact resistance close to that of fine silver. In comparison topure silver Therefore Pt and fine-grain silver AgCu3 exhibits increased mechanical strengthPd are typically used as well as higher arc erosion resistance alloys and mechanical wear resistance(Table 2.14)are rather not used in their pure form for electrical contact applications.

Hard-silver alloys are widely used for switching applications in the information==Tungsten and energy technology for currents up to 10 A, in special cases also for highercurrent ranges (Table 2.16).Molybdenum Based Materials==

Dispersion hardened alloys of silver with 0.5 wt% MgO Main Article: [[Tungsten and NiO (ARGODUR 32)are produced by internal oxidation. While the melt-metallurgical alloy is easy tocold-work Molybdenum Based Materials| Tungsten 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]]

ARGODUR 32 is mainly used in the form of The low gas content contact springs that materials are exposed tohigh thermal and mechanical stresses developed for the use in relays, and contactors for aeronauticapplicationsvacuum switching devices.

Fig. 2.47Main Article:Influence of 1-10 atom% of differentalloying metals on the electrical resistivity ofsilver[[Contact Materials for Vacuum Switches| Contact Materials for Vacuum Switches]]

FigVinaricky, E. 2(Hrsg.49): Coarse grain micro structureElektrische Kontakte, Werkstoffe und Anwendungen.of Ag 99Springer-Verlag, Berlin, Heidelberg etc.97 after 80% cold workingand 1 hr annealing at 600°C2002

FigLindmayer, M. 2.50: Fine grain microstructureof AgNi0Schaltgeräte-Grundlagen, Aufbau, Wirkungsweise.15 after 80% cold workingand 1 hr annealing at 600°CSpringer-Verlag, Berlin, Heidelberg, New York, Tokio, 1987

FigRau, G. 2: Metallische Verbundwerkstoffe.51:Phase diagramWerkstofftechnischeof silver-nickelVerlagsgesellschaft, Karlsruhe 1977

FigSchreiner, H. 2: Pulvermetallurgie elektrischer Kontakte.52:Springer-VerlagPhase diagramof silver-copperBerlin, Göttingen, Heidelberg, 1964

FigHansen. 2M.; Anderko, K.53:Phase diagram Constitution ofBinary Alloys. New York:silverMc Graw-cadmiumHill, 1958

Table 2Shunk, F.A.14: Mechanical Properties Constitution of Silver and Silver AlloysBinary Alloy. 2 Suppl. New York; Mc Graw-Hill, 1969

FigEdelmetall-Taschenbuch. 2( Herausgeber Degussa AG, Frankfurt a.54:Strain hardeningof AgCu3M.),by cold workingHeidelberg, Hüthig-Verlag, 1995

FigRau, G. 2: Elektrische Kontakte-Werkstoffe und Technologie.55:Eigenverlag G. RauSoftening of AgCu3after annealing for 1 hrafter 80% cold workingGmbH & Co., Pforzheim, 1984

FigHeraeus, W. 2C.56:Strain hardening of AgCu5 by coldworkingWerkstoffdaten. Eigenverlag W.C. Heraeus, Hanau, 1978

FigLinde, J. 2O.57:Elektrische Widerstandseigenschaften der verdünnten LegierungenSoftening of AgCu5 afterannealing for 1 hr after 80% coldworkingdes Kupfers, Silbers und Goldes. Lund: Hakan Ohlsson, 1938

FigGroßmann, H. 2Saeger, K. E.; Vinaricky, E.59:Gold and Gold Alloys in ElectricalSoftening of AgCu10 afterannealing for 1 hr after 80% coldEngineering. in: Gold, Progress in Chemistry, Biochemistry and Technology. JohnworkingWiley & Sons, Chichester etc, (1999) 199-236

FigGehlert, B. 2: Edelmetall-Legierungen für elektrische Kontakte.60:Strain hardening of AgCu28 bycold workingMetall 61 (2007) H. 6, 374-379

FigAldinger, F. 2; Schnabl, R.61:Edelmetallarme Kontakte für kleine Ströme.Softening of AgCu28after annealing for 1 hr after80% cold workingMetall 37 (1983) 23-29

FigBischoff, A. 2; Aldinger, F.62:Einfluss geringer Zusätze auf die mechanischenStrain hardening of AgNi0Eigenschaften von Au-Ag-Pd-Legierungen.15by cold workingMetall 36 (1982) 752-765

FigWise, E. 2M.63:Softening of AgNi0Palladium, Recovery, Properties and Uses.15after annealing for 1 hr after 80%New York, London:cold workingAcademic Press 1968

FigSavitskii, E. 2M.; Polyakova, V.P.; Tylina, M.A.64:Palladium Alloys, Primary Sources.Strain hardening ofARGODUR 27by cold workingNew York: Publishers 1969

FigGehlert, B. 2.65:Lebensdaueruntersuchungen von Edelmetall Kontaktwerkstoff-Softeningof ARGODUR 27 after annealingfor 1 hr after 80% cold workingKombinationen für Schleifringübertrager. VDE-Fachbericht 61, (2005) 95-100

Table 2Holzapfel,C.15: Contact and Switching Properties of Silver and Silver AlloysVerschweiß und elektrische Eigenschaften vonSchleifringübertragern. VDE-Fachbericht 67 (2011) 111-120

Table 2Schnabl, R.; Gehlert, B.16: Application Examples and Forms of Supply for Silver and Silver AlloysLebensdauerprüfungen von Edelmetall-Schleifkontaktwerkstoffen für Gleichstrom Kleinmotoren.Feinwerktechnik & Messtechnik (1984) 8, 389-393

===2Kobayashi, T.4; Koibuchi, K.2; Sawa, K.3 Silver-Palladium Alloys===The addition ; Endo, K.; Hagino, H.: A Study of 30 wt% Pd increases the mechanical properties as well as theLifetimeresistance of silver against the influence of sulfur Au-plated Slip-Ring and sulfur containingAgPd Brush System for Power Supply.compounds significantly (Tables 2th Proc. 24 Int.17 and 2Conf.18)on Electr.Alloys with 40Contacts, Saint Malo, France 2008, 537-60 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.542

AgPd alloys are hardHarmsen, arc erosion resistant, and have a lower tendency towardsmaterial transfer under DC loads (Table 2U.19); Saeger K. On the other hand the electricalconductivity is decreased at higher Pd contentsE. The ternary alloy AgPd30Cu5has an even higher hardness which makes it suitable for use in sliding contact: Über das Entfestigungsverhalten von Silbersystemsverschiedener Reinheiten.Metall 28 (1974) 683-686

AgPd alloys are mostly used in relays for the switching of medium to higher loads(>60VBehrens, V.; Michal, R.; Minkenberg, J.N.; Saeger, >2A) as shown in Table 2K.20E. Because of the high palladium price these: Abbrand undformerly solid contacts have been widely replaced by multiKontaktwiderstandsverhalten von Kontaktwerkstoffen auf Basis von Silber-layer designs suchas AgNi0Nickel.15 or AgNi10 with a thin Au surface layere. A broader field of applicationfor AgPd alloys remains in the wear resistant sliding contact systems& i. 107. Jg.(1990), 2, 72-77

FigBehrens, V. 2: Silber/Nickel und Silber/Grafit- zwei Spezialisten auf dem Gebietder Kontaktwerkstoffe. Metall 61 (2007) H.66: Phase diagram of silver6, 380-palladium384

FigRieder, W. 2.67:Silber / Metalloxyd-Werkstoffe für elektrische Kontakte,Strain hardeningof AgPd30 by cold workingVDE - Fachbericht 42 (1991) 65-81

FigHarmsen,U. 2.68:Die innere Oxidation von AgCd-Legierungen unterStrain hardeningSauerstoffdruck.of AgPd50 by cold workingMetall 25 (1991), H.2, 133-137

FigMuravjeva, E. 2M.; Povoloskaja, M.D.69:Verbundwerkstoffe Silber-Zinkoxid undStrain hardeningof AgPd30Cu5Silber-Zinnoxid, hergestellt durch Oxidationsglühen.by cold workingElektrotechnika 3 (1965) 37-39

FigBehrens, V. 2; Honig Th.; Kraus, A.70:Softening of AgPd30; Michal, AgPd50R.; Saeger,K.-E.; Schmidberger, R.;and AgPd30Cu5 after annealing of 1 hrStaneff, Th.: Eine neue Generation von AgSnO₂ -Kontaktwerkstoffen.after 80% cold workingVDE-Fachbericht 44, (1993) 99-114

Table 2Braumann, P.; Lang, J.17: Physical 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.18: Mechanical Properties of SilverProc. 20 Int. Conf. on Electr. ContactPhenom., Stockholm 2000, 193-Palladium Alloys198

Table 2Wintz, J.-L.; Hardy, S.; Bourda, C.19: Contact Influence on the Electrical Performances ofAssembly Process, Supports Materials and Switching Properties of SilverProduction Means for AgSnO₂ .Proc.24_th Int. Conf. on Electr. Contacts, Saint Malo, France 2008, 75-Palladium Alloys81

Table 2Behrens, V.; Honig, Th.; Kraus, A.; Michal, R.20: Application Examples and Forms of Suppl for SilverSchalteigenschaften vonverschiedenen Silber-Zinnoxidwerkstoffen in Kfz-Relais. VDE-Fachbericht 51(1997) 51-Palladium Alloys57

===2Schöpf, Th.4: Silber/Zinnoxid und andere Silber-Metalloxidwerkstoffe inNetzrelais.3 Silver Composite Materials===VDE-Fachbericht 51 (1997) 41-50

===2Schöpf, Th.4; Behrens, V.3; Honig, Th.; Kraus, A.1 : Development of SilverZincth Oxide for General-Nickel (SINIDUR) Materials===Since silver and nickel are not soluble in each other in solid form and in the liquidphase have only very limited solubility silver nickel composite materials withhigher Ni contents can only be produced by powder metallurgyPurpose Relays. 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 (FigsProc. 220 Int.75Conf. and 2on Electr.76)Contacts,Stockholm 2000, 187-192

The high density produced during hot extrusion aids the arc erosion resistanceof these materials (Tables 2Braumann, P.21 and 2; Koffler, A.22). The typical application of : Einfluss von Herstellverfahren, Metalloxidgehalt undWirkzusätzen auf das Schaltverhalten von Ag/Nicontact materials is SnO in devices for switching currents of up to 100A (Table Relais. 2.24).In this range they are significantly more erosion resistant than silver or silveralloys. In addition they exhibit with nickel contents <20 wt% a low and over theiroperational lifetime consistent contact resistance and good arc movingproperties. In DC applications Ag/Ni materials exhibit a relatively low tendencyof material transfer distributed evenly over the contact surfaces VDE-Fachbericht 59, (Table 2.232003).133-142

Typically Ag/Ni (SINIDUR) materials are usually produced with contents of 10-40wt% NiKempf, B.; Braumann, P. The most widely used materials SINIDUR 10 and SINIDUR 20- and alsoSINIDUR 15; Böhm, mostly used in north americaC.; Fischer-Bühner, are easily formable and applied bycladding (FigsJ. 2.71: Silber-Zinnoxid-2.74). They can be, without any additional welding aids,economically welded and brazed to the commonly used contact carriermaterialsWerkstoffe: Herstellverfahren und Eigenschaften.The Metall 61(SINIDUR2007) 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 forcesH.6, 404-408

The most important applications for Ag/Ni contact materials are typically inrelaysLutz, O.; Behrens, wiring devicesV.; Finkbeiner, appliance switchesM.; Honig, thermostatic controlsT.; Späth, auxiliaryD.: Ag/CdO-Ersatz inswitchesLichtschaltern. VDE-Fachbericht 61, and small contactors with nominal currents >20A (Table 2.242005).165-173

Table 2Lutz, O.; Behrens, V.; Wasserbäch, W.; Franz, S.; Honig, Th.; Späth,D.; Heinrich, J.21: Physical 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

Table 2Leung, C.; Behrens, V.22: Mechanical Properties A Review of SilverAg/SnO Contact Materials and Arc Erosion. 2th Proc.24 Int. Conf. on Electr. Contacts, Saint Malo, France 2008, 82-Nickel (SINIDUR) Materials87

FigChen, Z. 2K.; Witter, G.J.71:Comparison in Performance for Silver–Tin–IndiumOxide Materials Made by Internal Oxidation and Powder Metallurgy.Strain hardeningth Proc. 55 IEEE Holm Conf. on Electrical Contacts, Vancouver, BC, Canada,of Ag/Ni 90/10 by cold working(2009) 167 – 176

FigRoehberg, J. 2; Honig, Th.; Witulski, N.; Finkbeiner, M.; Behrens, V.72:PerformanceSoftening of AgDifferent Silver/Ni 90/10Tin Oxide Contact Materials for Applications in Low Voltageafter annealingth Circuit Breakers. Proc. 55 IEEE Holm Conf. on Electrical Contacts, Vancouver,for 1 hr after 80% cold workingBC, Canada, (2009) 187 – 194

FigMuetzel, T. 2; Braumann, P.; Niederreuther, R.73:Temperature Rise Behavior ofStrain hardeningof th Ag/Ni 80/20 by cold workingSnO Contact Materials for Contactor Applications. Proc. 55 IEEE Holm 2Conf. on Electrical Contacts, Vancouver, BC, Canada, (2009) 200 – 205

FigLutz, O. 2et al.74:Softening of AgSilber/Ni 80/20Zinnoxid – Kontaktwerkstoffe auf Basis der Innerenafter annealingOxidation fuer AC – und DC – Anwendungen.for 1 hr after 80% cold workingVDE Fachbericht 65 (2009) 167 – 176

FigHarmsen, U. 2; Meyer, C.L.75: Micro structure of Ag/Ni 90/10 a) perpendicular to the extrusion directionMechanische Eigenschaften stranggepresster Silber-bGraphit-Verbundwerkstoffe. Metall 21 (1967) parallel to the extrusion direction, 731-733

FigBehrens, V. 2: Mahle, E.; Michal, R.; Saeger, K.E.76: Micro structure of AgAn Advanced Silver/Ni 80/20 a) perpendicular to the extrusion directionGraphiteth Contact Material Based on Graphite Fibre. Proc. 16 Int. Conf. on Electr.b) parallel t o the extrusion directionContacts, Loghborough 1992, 185-189

Table 2Schröder, K.-H.; Schulz, E.-D.23: Contact and Switching Properties of SilverÜber den Einfluss des Herstellungsverfahrensth auf das Schaltverhalten von Kontaktwerkstoffen der Energietechnik. Proc. 7 Int.Conf. on Electr. Contacts, Paris 1974, 38-Nickel (SINIDUR) Materials45

Table 2Mützel, T.24: Application Examples and Forms of SupplyNiederreuther, R.: Kontaktwerkstoffe für Hochleistungsanwendungen.for SilverVDE-Nickel Bericht 67 (SINIDUR2011) Materials103-110

===2Lambert, C.4.3; Cambon, G.2: Silver-Metal Oxide Materials Ag/CdO, Ag/SnO , Ag/ZnO===The family Influence of silver-metal oxide contact materials includes the material groups:silver-cadmium oxide (DODURIT CdO), silver-tin oxide (SISTADOX), Manufacturing Conditions and silverzincoxide (DODURIT ZnO). Because Metalurgical Characteristics on the Electrical Behaviour of their very good contact and switchingproperties like high resistance against welding, low contact resistance, and higharc erosion resistance, silverSilver-metal oxides have gained an outstanding positionGraphitein a broad field of applicationsth Contact Materials. Proc. 9 Int. Conf.on Electr. They mainly are used in low voltage electricalswitching devices like relays, installation and distribution switches, appliancesContacts,industrial controlsChicago 1978, motor controls, and protective devices (Table 2.13).401-406

*SilverVinaricky, E.: Grundsätzliche Untersuchungen zum Abbrand-cadmium oxide undSchweißverhalten von Ag/C-Kontaktwerkstoffen. VDE-Fachbericht 47 (DODURIT CdO1995) materials159-169

Silver-cadmium oxide (DODURIT CdO) materials with 10-15 wt% are producedby bothAgte, C.; Vacek, internal oxidation and powder metallurgical methods (Table 2J.25): Wolfram und Molybdän.Berlin: Akademie-Verlag 1959

The manufacturing of strips and wires by internal oxidation starts with a moltenalloy of silver and cadmiumKeil, A.; Meyer, C.-L. 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 or: Der Einfluß des Faserverlaufes auf die elektrischeless fine particle precipitation inside the Ag matrixVerschleißfestigkeit von Wolfram-Kontakten. The CdO particles are ratherfine in the surface area and are becoming larger further away towards the centerof the material ETZ 72, (Fig. 2.831951).343-346

During the manufacturing of Ag/CdO contact material by internal oxidation theprocesses vary depending on the type of semi-finished material.For Ag/CdO wires a complete oxidation of the AgCd wire is performedSlade, followedby wire-drawing to the required diameter (FigsP. 2G.77 and 2: Electric Contacts for Power Interruption.78)A Review. The resultingmaterial is used for example in the production of contact rivetsProc. 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 asmall depletion area in the center of it's thickness and a Ag backing suitable foreasy attachment by brazing (sometimes called “Conventional Ag/CdO”)19 Int. Usinga technology that allows the partial oxidation of a dual-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 (FigConf. 2.85)on Electric Contact Phenom. These materials Nuremberg (DODURIT CdO ZHGermany) are mainlyused as the basis for contact profiles and contact tips.1998, 239-245

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 a: Variations in Contact Resistance Resulting from Oxide Formationuniform and fine dispersion of CdO particles Decomposition in the AgW and Ag matrix while at the same-WC-C Contacts Passing Steady Currentstime achieving a high density which is advantageous for good contact properties(FigLong Time Periods. 2IEEE Trans.84)Components, Hybrids and Manuf. Technol. To obtain a backing suitable for brazing, a fine silver layer is appliedby either comCHMT-pound extrusion or hot cladding prior to or right after the extrusion9,1 (Fig. 2.861986).3-16

For larger contact tipsSlade, P. G.: Effect of the Electric Arc and especially those with a rounded shape, the single tipPress-Sinter-Repress process (PSR) offers economical advantages. Thepowder mix is pressed in a die close to the final desired shape, Ambient Air on the “green” tipsContactare sinteredResistance of Silver, Tungsten and in most cases the repress process forms the final exact shapeSilver-Tungsten Contacts.while at the same time increasing the contact density and hardnessJ.Appl.Phys.47, 8 (1976) 3438-3443

Using different silver powders Lindmayer, M.; Roth, M.: Contact Resistance and minor additives for the basic Arc-Erosion of W-Ag and CdOstarting materials can help influence certain contact properties for specializedWC-Ag. IEEE Trans components, Hybrids and Manuf. Technol.applications.CHMT-2, 1 (1979) 70-75

FigLeung, C. 2-H.; Kim, H.J.77:Strain hardening A Comparison of internally oxidizedAg/CdO 90W, Ag/WC and Ag/10 by cold workingMo ElectricalContacts. IEEE Trans. Components, Hybrids, Manuf. Technol.,Vol. CHMT-7, 1 (1984) 69-75

FigAllen, S. 2E.; Streicher, E.78:The Effect of Microstructure on the ElectricalSoftening th Performance of internally oxidizedAg/CdO 90/10 after annealing-WC-C Contact Materials. Proc. 44 IEEE Holm Conf. on Electr.for 1 hr after 40% cold workingContacts, Arlington, VA, USA (1998), 276-285

Table 2Haufe, W.; Reichel, W.; Schreiner H.25: Physical and Mechanical Properties as well as Manufacturing Processes andForms of Supply of Extruded Silver Cadmium OxideAbbrand verschiedener W/Cu-Sinter-Tränkwerkstoffe an Luft bei hohen Strömen. Z. Metallkd. 63 (DODURIT CdO1972) Contact Materials651-654

FigAlthaus, B. 2; Vinaricky, E.79:Das Abbrandverhalten verschieden hergestellterStrain hardening ofWolfram-Kupfer-Verbundwerkstoffe im Hochstromlichtbogen.Ag/CdO 90/10 P by cold workingMetall 22 (1968) 697-701

FigGessinger, G. 2H.; Melton, K.N.80: SofteningBurn-off Behaviour of Ag/CdO 90/10 P after annealingWCu Contact Materials in anfor 1 hr after 40% cold workingElectric Arc. Powder Metall. Int. 9 (1977) 67-72

FigMagnusson, M. 2.81:Abbrandverhalten und Rißbildung bei WCu-TränkwerkstoffenStrain hardeningof Ag/CdO 88/12 WPunterschiedlicher Wolframteilchengröße. ETZ-A 98 (1977) 681-683

FigHeitzinger, F. 2; Kippenberg, H.; Saeger, K.E.; Schröder, K.H.82:Softening of Ag/CdO 88/12WP after annealingContact Materials for 1 hr after different degrees ofcold workingVacuum Switching Devices. Proc. XVth ISDEIV, Darmstadt 1992, 273-278

FigGrill, R. 2; Müller, F.83: Micro structure of Ag/CdO 90/10 iVerbundwerkstoffe auf Wolframbasis fürHochspannungsschaltgeräte.oMetall 61 (2007) H. a) close to surfaceb) in center area6, 390-393

FigSlade, P. 2: G.84: Micro structure of Ag/CdO 90/10 P:a) perpendicular to extrusion directionThe Vacuum Interrupter- Theory; Design; and Application. CRCbPress, Boca Raton, FL (USA) parallel to extrusion direction, 2008

FigFrey, P. 2; Klink, N.; Saeger, K.E.85:Untersuchungen zum Abreißstromverhalten vonMicro structure of Ag/CdO 90/10 ZH:1) Ag/CdO layer2Kontaktwerkstoffen für Vakuumschütze. Metall 38 (1984) AgCd backing layer647-651

FigFrey, P. 2; Klink, N.; Michal, R.; Saeger, K.E.86: Micro structure Metallurgical Aspects of AgCdO 88/12 WP: aContactMaterials for Vacuum Switching Devices. IEEE Trans. Plasma Sc. 17, (1989) perpendicular to extrusion direction743-b) parallel to extrusion direction740

*Silver–tin oxide(SISTADOX)materialsOver the past yearsSlade, many Ag/CdO contact materials have been replaced byP.: Advances in Material Development for High Power Vacuum InterrupterAg/SnO based materials with 2-14 wt% SnO 2 2 because of the toxicity ofCadmiumth Contacts. Proc.16 Int. Conf. This changeover was further favored by the fact that Ag/SnO2contacts quite often show improved contact and switching properties such aslower arc erosion, higher weld resistance, and a significant lower tendencytowards material transfer in DC switching circuits (Table 2on Electr.30)Contact Phenom. Ag/SnO2materials have been optimized for a broad range of applications by other metaloxide additives and modification in the manufacturing processes that result in,different metallurgicalLoughborough 1992, physical and electrical properties (Table 2.29).1-10

Manufacturing of Ag/SnO2 by ''internal oxidation'' is possible in principleBehrens, V.; Honig, butduring heat treatment of alloys containing > 5 wt% of tin in oxygenTh.; Kraus, dense oxidelayers formed on the surface of the material prohibit the further diffusion ofoxygen into the bulk of the materialA. By adding Indium or Bismuth to the alloy theinternal oxidation is possible and results in materials that typically are rather hardand brittle and may show somewhat elevated contact resistance and is limitedto applications in relays; Allen, S. To make a ductile material with fine oxide dispersion: Comparison of Different Contact(SISTADOX TOS F) (Fig. 2th Materials for Low Voltage Vacuum Applications.114) it is necessary to use special process variationsin oxidation and extrusion which lead to materials with improved properties inrelaysProc. Adding a brazable fine silver layer to such materials results in a semifinishedmaterial suitable for the manufacture as smaller weld profiles(SISTADOX WTOS F) (Fig19 Int. 2Conf.116)on Electr. Because of their resistance to materialtransfer and low arc erosion these materials find for example a broaderapplication in automotive relays (Table 2.31)Contact Phenom., Nuremberg 1998, 247-251

''Powder metallurgy'' plays a significant role in the manufacturing of Ag/SnO2contact materialsRolle, S.; Lietz, A. Besides SnO2 a smaller amount (<1 wt%) of one or moreother metal oxides such as WO3; Amft, MoO3D.; Hauner, CuO and/or Bi2O3 are addedF. These: CuCr Contact Material for Low Voltageadditives improve the wettability of the oxide particles and increase the viscosityof the Ag meltth Vacuum Contactors. Proc. 20 int. Conf. on Electr. They also provide additional benefits to the mechanical andarcing contact properties of materials in this group ''(Table 2Contact.26)''Phenom.Stockholm2000, 179-186

In the manufacture the initial powder mixes different processes are appliedKippenberg, H.: CrCu as a Contact Material for Vacuum Interrupters.which provide specific advantages of the resulting materials in respect to theircontact properties ''(Figs. 2th Proc.87 – 213 Int.119)''Conf. Some of them are described here asfollows::'''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 powderson Electr. The blending is usually performed in the dry stage in blenders of different designContact Phenom.Lausanne 1986, 140-144

:b) '''Powder blending on the basis of doped powders'''For incorporation of additive oxides in the SnO powder the reactive spray 2process (RSV) has shown advantagesHauner, F. This process starts with a waterbasedsolution of the tin and other metal compounds; Müller, R. This solution isnebulized under high pressure and temperature in a reactor chamber; Tiefel, R.: CuCr für Vakuumschaltgeräte-Through the rapid evaporation of the water each small droplet is convertedinto a salt crystal and from there by oxidation into a tin oxide particle in whichthe additive metals are distributed evenly as oxidesHerstellungsverfahren, Eigenschaften und Anwendung. The so created dopedAgSnO powder is then mechanically mixed with silver powder.cMetall 61 (2007) Powder blending based on coated oxide powdersIn this process tin oxide powder is blended with lower meting additive oxidessuch as for example Ag MoO and then heat treatedH. The SnO particles are 2 4 2coated in this step with a thin layer of the additive oxide.d) Powder blending based on internally oxidized alloy powderse) Powder blending based on chemically precipitated compoundpowders6, 385-389