Homogenization Heat Treatment and Tribological Properties of In Situ Alloyed NiTiCu by Laser Powder‐Bed Fusion

Abstract

In situ alloying by additive manufacturing (AM) of premixed powders has been recognized as a promising low‐cost method for creating complex parts for biomedical implants, in which homogenization heat treatment is a critical concern in this technology. Also, as promising implant materials, their tribological properties under dry and lubrication conditions are significantly concerned with evaluating the functionalities of 3D printing. This work preliminarily addresses these two concerns with the laser powder‐bed fusion (LPBF) 3D‐printed nickel titanium copper (NiTiCu) alloy using three homogenization heat treatments and ball‐on‐disc wear tests under dry and NaCl‐lubricated conditions. It is found that to achieve sufficiently good microstructural homogeneity with low porosity, a temperature of 800 °C and a duration of 5 h is needed. Despite the promising outcome, analysis of the results revealed that all heat treatments led to the formation of a secondary phase identified as Ti2(Ni,Cu), which induced two‐step phase transformations. Thus, further studies on the optimization of the postprocessing techniques are required. The heat‐treated alloy resulting in the most favorable properties is selected for tribological testing. AM and the addition of Cu are observed to enhance the wear resistance of the alloy under lubrication conditions.