Tribomechanical Properties of Ion Implanted Metals

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Abstract
A review of tribomechanical studies supported by surface analysis finds ion implantation capable of increasing the sliding wear resistance of ion implanted metals in two ways. First, it can reduce friction by modifying the surface composition (e.g. Ti+ into steel) or by promoting the growth of low friction oxide layers (e.g. N into Ti). Second, it can modify the subsurface composition and structure to resist fracture and debris formation. These modifications harden the surface, change its work-hardening behavior and/or increase residual stresses. Microindentation hardness measurements indicate that many but not all of the wear resistant surfaces are hardened by implantation; thus, surface hardness is a contributing but not necessarily a controlling factor in wear resistance. These mechanisms of wear reduction and the chemical and microstructural modifications responsible for them are discussed. Evidence for wear reduction through the migration of N during wear is critically reviewed. It is concluded that the principal benefit of ion implantation is to prevent or delay the formation of wear particles, thereby changing the wear mode during run-in and permitting metals to reach load-carrying capacities up to their elastic limits.