Effect of V and Cr transition layers on microstructure and mechanical properties of Ni-based coating on titanium alloy fabricated by laser cladding

Abstract

Abstract In current study, the Inconel 718 coating was prepared on the surface of Ti-6Al-4V by laser cladding. The transition composition route of Ti-6Al-4V alloy\xa0→\xa0V\xa0→\xa0Cr\xa0→\xa0Inconel 718 was designed to relieve tremendous differences of Ti and Ni in thermal physics properties and refrain undesirable intermetallic compounds at the interface between Inconel 718 coating and Ti-6Al-4V substrate. The microstructure and composition of different layers were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and electron back-scatter diffraction (EBSD). The mechanical properties of the coating were examined by Vickers hardness tester and nanoindentation tester. The friction and wear properties of the Inconel 718 coating was evaluated from 30°C to 800\xa0°C in air against Si3N4 counterpart. Results show that the V and Cr transition layers are composed of V bcc and Cr bcc respectively, without undesirable intermetallic compounds. The Inconel 718 coating contains γ-Ni(Cr, Fe) and (Ni,Ti,Al) solid solutions as well as Ni4Nb and Ni0.45V0.55 intermetallic compounds. Due to the diffusion of V element into the Inconel 718 coating, the segregation of Nb was improved and the formation of Laves phase was inhibited. The strengthening effect of intermetallic compounds leads to a remarkable increase in the mechanical properties of the coating compared with Ti-6Al-4V substrate. The Inconel 718 coating suffers from abrasive wear and micro-cutting at low and middle temperature, while exhibits superior wear resistance due to the formation of the glazed layer at high temperature.