Microstructure and wear resistance of compositionally graded Ti[sbnd]Al intermetallic coating on Ti6Al4V alloy fabricated by laser powder deposition

Abstract

In this study, a compositionally graded TiAl intermetallic coating has been successfully fabricated by laser powder deposition (LPD) with Ti6Al4V and AlSi10Mg powder. The microstructure, composition distribution and phase structure of the graded TiAl intermetallic coating were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), electron probe microanalysis (EPMA) and micro-area X-ray diffraction analysis (XRD). In order to evaluate the wear resistance of the graded TiAl intermetallic coating, the sliding wear test was performed. Besides, the morphologies of the worn surface were analyzed by SEM and confocal microscope. The results show that the coating had a crack-free and well-graded compositional microstructure. Intermetallic Ti3Al, TiAl, TiAl3 and Ti5Si3 hard phase were the dominant constructive phases of the graded TiAl intermetallic coating. These phases enhanced the micro-hardness of the graded coating and consequently improved its wear resistance. The average friction coefficient and the wear rate of the graded TiAl intermetallic coating were 0.3704 and 1.989 × 10−4 mm3/Nm, respectively, which were significantly lower than those of the substrate (0.5667 and 8.384 × 10−4 mm3/Nm). The wear mechanism of the coating was mainly abrasive wear. Based on our finding, the graded TiAl intermetallic coating is a promising wear resistant coating for Ti6Al4V alloy.