Chapter 7-Lubricated Wear Tests

THE PURPOSE OF MOST WEAR TESTS IS TO SIMUlate a specific situation, a type of motion, frequency, speed, etc. Of course, some tribosystems involve the use of lubricants. Thus, representative bench tests also use lubrication-a lubricated wear test, which is the primary subject of this chapter. The objective of a lubricated wear test is often to determine the efficacy of a particular material couple when lubricated in a specific way. There are also tests, called lubricant tests, that keep the material couple constant and test the friction or wear reduction characteristics of lubricants, although these tests are not included in the chapter scope. The evaluation of lubricants is such a large subject that it could not be properly addressed in one short chapter. In addition, there are a plethora of lubricant tests that address characteristics other then their friction and wear reduction capabilities. For example, oil tests include biodegradability, viscosity, foaming, acidity, and contaminants. Grease tests include tests to assess stiffness (cone penetration), corrosivity, evaporation characteristics, and separation characteristics. Solid film lubricant tests include corrosivity, adhesion, and shock resistance. Screening lubricants requires more than wear tests. The chapter objective is knowledge of wear tests that can be used to screen material couples in the lubricated condition. This chapter will describe important lubricant families and then discuss some of the more commonly used ASTM and nonstandard tests. Many important lubricant terms were defined in Chapter 1. Additional terms will be defined as needed. We will discuss ASTM standard tests and then some nonstandard tests.