Sintered metallic friction material

Sintered Metal Friction Materials Under Dry Conditions (vol. 2.05, p. 223-225, 1989)... 

Friction Materials. Sintered friction materials are classified as metal— nonmetal combinations (49,50). These are best manufactured by the P/M process. Clutch plates, brake bands, brake blocks, and packing compositions are examples of friction materials (see Brake linings and clutch facings). 

A sintered friction material is composed of a metal matrix, generally mainly copper, to which a number of other metals such as tin, zinc, lead, and iron are added. Important constituents include graphite and friction-producing components such as siHca, emery, or asbestos. 

Sintered Materials or Cermets. Heavy weights and high landing speeds of modem aircraft or high speed trains require friction materials that ate extremely stable thermally. Organic or semimetallic friction matenals ate frequendy unsatisfactory for these appHcations. Cermet friction materials ate metal-bonded ceramic compositions (see Composite materials) (12—14). The metal matrix may be copper or iron (15). 

Metals such as copper, iron, or a combination of the two, usually modified with tin, bismuth, and/or lead ate used as binders of sintered friction materials where deformation under the high forming pressure is requited to lock together the property modifiers within a matrix. Metals such as copper, iron, zinc, aluminum, and occasionally lead are also used as friction modifiers. 

For automatic transmissions where the clutch is immersed in oil, paper-based clutch facings are employed. For tmcks and heavy off-road equipment, cermet friction materials are also used. Sintered cermet segments are attached to a metal plate to form the clutch facing. 

These are iron- and copper-based inorganic friction materials used for severe applications like tractor clutches, train, and aircraft brakes. Sintered metallic formulations contain lubricants like graphite, abrasives, and other property modifiers held together by metal binders like copper and iron. Sintered friction materials are normally fabricated as buttons that are riveted or fused to a carrier plate or cup. These friction materials are well suited for heavy-duty applications and find use in either dry or oil-immersed applications. 

Metal powders and flbers like iron, tin, copper, brass, and bronze are used as binders in sintered formulations. Powder metallurgy processes are used to fabricate these friction materials. 

Fibers and chips of nonferrous metals and alloys like copper, brass, aluminum, zinc, and bronze are used in friction materials to provide the desired friction and wear performance. Porous and solid metal powders like tin, brass, copper, bronze, and iron are also used in some products. As mentioned earlier, some metal powders are also used as binders in sintered formulations. 

Metal-matrix composites using TiC as the reinforcing phase have also been used as tool materials for copper alloys (Ref 26). Both sintered TiC Ni W and hipped TiC Ni Mo alloys were used to friction stir copper alloys. However, both TiC-containing alloys produced brittle tools that fractured during the tool plunge. 

While cermets have a hardness similar to sintered hard metals, these are less sensitive to diffusion and they have a better friction and wear behavior. They are capable of machining at speeds higher than those used for sintered hard metals. They excel in the semi-finish turning and milling and finishing of steels and stainless steels. The material properly deficiencies between high-speed steels and sintered hard metals is made up by the composites consisting of a dispersion of TiC or, less... 

---