Tribological behaviour of alumina sliding on several kinds of materials

Friction and wear behaviour of alumina sliding on various materials (nickel, copper, titanium, aluminium, alumina) were investigated experimentally. Pin-on-disc tests were conducted in air at various relative humidity levels (RHL). The results show that the influence of humidity depends on the material of the couples. Tribological behaviour of alumina sliding on very reactive metals such as titanium and aluminium is not influenced by RHL. In contrast, the friction coefficient and wear mechanism of nickel and copper are strongly affected by adsorbed films of water vapour. Nickel implanted with boron was also studied. The friction and wear of implanted surfaces are drastically reduced due to a lowering of the nickel surface reactivity. The tribological behaviour of the Al₂O₃/Al₂O₃ couple is also sensitive to RHL. The variation of friction coefficient and wear of this system are discussed in terms of tribochemical reactions and crack propagation.