Densification, Microstructure, and Wear Property of In Situ Titanium Nitride-Reinforced Titanium Silicide Matrix Composites Prepared by a Novel Selective Laser Melting Process

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2012-02, Vol.43 (2), p.697-708
• Main Authors: Gu, Dongdong, Hong, Chen, Meng, Guangbin
• Format: Article
• Language: English
• Subjects: Applied sciences; Characterization and Evaluation of Materials; Chemistry and Materials Science; Composite materials; Contact of materials. Friction. Wear; Densification; Energy density; Exact sciences and technology; Lasers; Materials Science; Mechanical properties; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Melting; Metallic Materials; Metallurgy; Metals. Metallurgy; Microhardness; Microstructure; Nanotechnology; Production techniques; Strain hardening; Structural Materials; Surface treatment; Surfaces and Interfaces; Thin Films; Titanium alloys; Titanium nitride; Wear
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-011-0876-8

This work presents the densification behavior, microstructural features, microhardness, and wear property of in situ TiN/Ti 5 Si 3 composite parts prepared by a novel Selective Laser Melting (SLM) process. The occurrence of balling phenomenon at a low laser energy density combined with a high scan speed and the formation of thermal cracks at an excessive laser energy input generally decreased densification rate. The in situ -formed TiN reinforcing phase experienced a successive morphological change: an irregular polyangular shape—a refined near-round shape—a coarsened dendritic shape, as the applied laser energy density increased. The variations in liquid-solid wettability and intensity of Marangoni convection within laser molten pool accounted for the different growth mechanisms of TiN reinforcement. The TiN/Ti 5 Si 3 composite parts prepared under the optimal SLM conditions had a near-full 97.7 pct theoretical density and a uniform microhardness distribution with a significantly increased average value of 1358.0HV 0.3 . The dry sliding wear tests revealed that a considerably low friction coefficient of 0.19 without any apparent fluctuation and a reduced wear rate of 6.84 × 10 −5 mm 3 /Nm were achieved. The enhanced wear resistance was attributed to the formation of adherent strain-hardened tribolayer covered on the worn surface.