Performance Assessment of Ni-Coated Titanium Alloys Under Wet Conditions

Abstract

Since its first introduction in the 1950s, Ti6Al4V became the most sympathetic titanium alloy due to its attractive mechanical and physicochemical properties and is currently extensively used, for e.g., in machining, automotive, aerospace, as well as biomedical industry. However, its poor tribological properties limit its use in machining, automotive, aerospace, and orthopedic applications. Hence, a variety of attempts have been made in order to improve tribological performance of titanium alloys, especially focusing on surface modification. This paper represents an overview of significance of surface modification applied on Ti6Al4V alloy. Several solutions have been followed to improve the machinability of these alloys: development of new machining techniques, tool geometries, and protection of tools??? surface with coatings to yield high productivity, good surface finish of the work-piece, and extended tool life. In this work, Ni coating on Ti-based alloys is tested to evaluate their potential for machining as well as for biomedical applications. The tribological behavior is evaluated at room temperature in wet lubricated conditions on pin-on-disk equipment, by testing Ni-coated pins of 10 mm diameter and 30 mm long against EN-31 flat plate. Friction coefficient of coated pins in wet condition is observed to be less, as compared to the tests performed with uncoated pins. Coated sample tested in lubricated condition showed much more reduction in wear and friction coefficient than their performance under uncoated condition. From experimental investigation, it is observed that the Ti alloys with Ni coating show improved wear rate and friction coefficient as compared to without coating.