Formation of commercially pure titanium with a bimodal nitrogen diffusion phase using plasma nitriding and spark plasma sintering

CP titanium with a bimodal microstructure consisting of a substrate surrounded by a network structure of nitrogen diffusion phase was fabricated by sintering nitrided powders, as a means of improving the mechanical and tribological properties. A nitrogen diffusion layer can be formed on CP titanium powder at temperatures above 873 K. The areal fraction of the nitrogen diffusion phase increased along with the sintering temperature. As results of ball-on-disk dry friction tests, CP titanium fabricated from powder nitrided at 873 K had a lower friction coefficient than compacts fabricated from as-received CP titanium powder. In contrast, adhesion of the counter material was observed over the worn surface of sintered compact fabricated from the powder nitrided at 973 K, which indicates a higher friction coefficient. (C) 2018 Elsevier B.V. All rights reserved.