Air conditioning systems are routinely employed within automobiles and other vehicles for creating comfortable conditions within the passenger compartment for the vehicle occupants. At outside temperatures above about 70.degree. F., it is difficult to maintain a comfortable passenger compartment temperature without first cooling the air that is being blown into the passenger compartment. Typically, cooling of the air is accomplished by first compressing an appropriate refrigerant, such as the generally used fluorocarbons (known commonly as freon) or another alternative refrigerant, using an engine-driven compressor which compresses the vaporized refrigerant.
The materials and components within the air conditioning system must be capable of withstanding extremely demanding conditions, particularly, the materials used to form the components within the engine driven compressor. The compressor contains many mating components which continuously wear against each other during operation of the air conditioning system, while also being subject to significant pressures due to the compressed refrigerant. Appropriate lubricants are provided throughout the compressor at these bearing surfaces, so as to prevent excessive wear and galling between the mating materials. Typically in the past, a lubricant which is soluble in the refrigerant has been added directly in with the refrigerant when charging the compressor with the pressurized refrigerant prior to use. Since the conventional lubricants have been soluble within the refrigerant, the lubricant therefore moves freely through the compressor with the refrigerant, thereby providing lubrication where it is needed most between mating components.
However, due to environmental concerns, the current fluorocarbon-based refrigerants are being eliminated from use. Alternative refrigerants which alleviate environmental damage have been tested, with a 1,1,1,2-Tetrafluoroethane refrigerant, known as R134A, being a likely substitute. Unfortunately, conventional lubricants which have been previously (and successfully) employed with the fluorocarbon-based refrigerants are not soluble within the R134A refrigerant. Therefore the lubricant does not freely move throughout the compressor components when the new refrigerant is used and does not lubricate mating surfaces, as was the situation when the fluorocarbon-based refrigerants were used. The result is that during operation of the air conditioning system with the new R134A refrigerant, the bearing surfaces of the mating components are not lubricated and correspondingly they experience significantly higher incidence of wear.
Therefore, in the absence of an appropriate lubricant, it is necessary to provide a wear resistant material which is essentially self-lubricating. The desired material must be capable of not only providing sufficient lubricity, but must also be sufficiently strong to resist wear and galling during operation of the compressor. In addition, there are certain applications wherein the material must also be sufficiently ductile to permit the formation of a component from the material such as by swaging or other forming techniques. Therefore, the requirements of this material are many.