Microstructure and wear properties of LENS^® deposited medical grade CoCrMo

Abstract

There is a growing interest in metal-on-metal bearing surfaces for orthopedic implants. Although some success has been achieved in applications like hip implants which involve a large contact area, non-conforming joints, such as knees, have proved more difficult. The current work examines the applicability of a novel additive manufacturing process, Laser Engineered Net Shaping (LENS^®, the registered trademark and service mark of Sandia National Laboratories and Sandia Corporation), for producing CoCrMo implants. A series of experiments were conducted to determine the optimum parameters for deposition of CoCrMo. Microstructural studies, hardness tests, and dry sand/rubber wheel abrasive wear tests were conducted on the LENS^® deposits. The results showed that metallurgically sound deposits can be produced using the LENS^® process under optimized conditions. The hardness of the LENS^® deposited CoCrMo was found to be comparable to that of standard CoCrMo wrought material; however, wear tests indicated that LENS^® deposits were considerably less resistant to abrasive wear than wrought CoCrMo. The reasons for this behaviour are discussed based on microstructural observations.