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

Abstract

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 9 10 À5 mm 3 /Nm were achieved. The enhanced wear resistance was attributed to the formation of adherent strainhardened tribolayer covered on the worn surface.

An overview of additively manufactured metal matrix composites: preparation, performance, and challenge

“…TMCs with TiN and Ti 5 Si 3 reinforcements can also be fabricated via the in-situ reaction of 9Ti + Si 3 N 4 → 4TiN + Ti 5 Si 3 . This method was employed by Gu et al [300,301] to fabricate (TiC + Ti 5 Si 3 )/Ti composites and the resulting composites demonstrated significant improvements in hardness and wear resistance compared to pure Ti. Similarly, (TiC + Ti 5 Si 3 )/Ti composite can be produced by the addition of SiC [215].…”

Selective Laser Melting to Manufacture “In Situ” Metal Matrix Composites: A Review

“…SLM production of “in situ” TiN/TiC/Ti 5 Si 3 reinforcements has been attempted in Ti powder systems by using the SLM process . For these composites, the main exploited mechanisms are: Or Or …”

“…In another work, Gu et al used a stoichiometric composition according to Equation (i.e., Ti:Si 3 N 4 molar ratio of 9:1) to prepare balled‐milled powder for the SLM process. After SLM, they observed phase changes to a composite with TiN secondary phases in Ti 5 Si 3 matrix (Figure ).…”