The effect of countersurface thermal properties on the melt wear of aluminum

Abstract

The effect thermal properties of countersurface materials may have on the melt wear of aluminum is investigated. Aluminum (6061 T6) rod specimens were tested in a ring-on-rod configuration against five different ring countersurface materials: stainless steel (304); steel (4130); aluminum (6061 T6); copper (C101); and Glidcop (Al-25). In each test, sliding contact was produced for a brief 2s duration at pressure p = 1.76 MPa and speed v = 5.6 m/s during which friction was measured while rod wear was characterized by post-test mass measurement. At this common combination of contact pressure and sliding speed, heated tests against each countersurface material were conducted at far-field surrounding temperatures of 260, 300 and 330 °C. Aluminum rod wear rates ranged from 102 × 10 −3 mm 3/Nm against stainless steel to 1.23 × 10 −3 mm 3/Nm against copper at 330 °C, from 59.0 × 10 −3 mm 3/Nm against stainless steel to 0.66 × 10 −3 mm 3/Nm against copper at 300 °C, and from 30.9 × 10 −3 mm 3/Nm against stainless steel to 0.68 × 10 −3 mm 3/Nm against copper at 260 °C. Baseline tests were also conducted at room temperature, where rod wear rates all remained below 0.5 × 10 −3 mm 3/Nm as rod melt could not be achieved by sliding contact with any of the ring countersurfaces at such low far-field temperatures for the given contact pressure and sliding speed conditions. In heated tests, rod wear increases with increasing bulk temperature, since a smaller portion of the frictional heat is required to bring the sliding interface to the aluminum rod's melt temperature, thus leaving a greater balance of the frictional heat to go into the aluminum rod's phase change and melt wear. Rod melt wear increases with variation of ring countersurface material as follows: copper; Glidcop; aluminum; steel; stainless steel. This variation was found to be in agreement with the analytical prediction of the ring material's conduction effectiveness in partitioning heat away from the contact interface, thus reducing the heat going into the aluminum rod and its melting.