Chapter 5-Adhesive Wear Testing

AS WAS PREVIOUSLY MENTIONED, THE TERM “adhesive” essentially defines a wear mechanism, and mechanisms are seldom universally agreed upon. In addition, the term “adhesive wear” is not popular, but for this guide, it is preferred over the “nonabrasive” alternate term. Many times, the “adhesive” component may be minor, but “nonabrasive” may have no meaning to newcomers in tribology. In any case, the ASTM G 40 definition is: “wear due to localized bonding between contacting solid surfaces leading to material transfer between the two surfaces or loss from either surface.” There are several major types of wear in this category: • Sliding wear: any solid sliding on any other solid • Galling: severe form of adhesive wear • Scoring/scuffing wear: grooves and scratches in the sliding direction • Oxidative wear: mild wear in hard/hard unlubricated ferrous systems In addition, there are four types of relative sliding to consider • Unidirectional continuous • Reciprocating • Complex (slide, roll, etc.) • Intermittent Discussion will be limited to tests that are unidirectional, continuous, or reciprocating because most of the standard tests fall into these two types of sliding. Complex sliding is used, for example, in tests that simulate human joints in which motions are reciprocating combined with articulation. Intermittent motion tests are mostly employed in special tests to simulate an application. For example, photographic lenses in satellites are programmed to be translated by ball screws with a sequence that may consist of 70 clockwise rotations followed by 10 counterclockwise, then a dwell and then 30 rotations back, etc. The four types of adhesive wear will be addressed with standard and non-standard tests. The chapter will conclude with test selection remarks.