Microstructure and dry sliding wear behavior of plasma transferred arc clad Ti5Si3 reinforced intermetallic composite coatings

Abstract

In order to modify the tribological properties of titanium alloy, Ti53–Si32–Ni15, Ti43–Si26–Ni31 and Ti30–Si18–Ni52 (at.%) elemental powders blends were designed to fabricate Ti5Si3 reinforced intermetallic composite coatings on Ti–6Al–4V titanium alloy substrate by plasma transferred arc (PTA) cladding process. Microstructure of the PTA cladding coatings was characterized by SEM, XRD and EDS. The relationship between Ti/Si/Ni atomic ratios of the Ti–Si–Ni elemental powders blends and microstructure of the PTA cladding coatings was investigated in detail. The effect of volume fraction of the Ti5Si3 primary phases on microhardness and room temperature dry sliding wear behavior of the PTA cladding coatings was discussed. Results show that the PTA clad intermetallic composite coatings have a non-equilibrium solidified super-fine microstructure consisting of Ti5Si3 primary phases, NiTi2/α-Ti/Ti5Si3 ternary eutectics and a small amount of NiTi2/Ti5Si3 binary eutectics. The PTA clad composite coatings are metallurgically bonded to the Ti–6Al–4V titanium alloy substrate. The Ti/Si/Ni atomic ratios of the Ti–Si–Ni elemental powders blends have a noticeable effect on grain size, volume fraction and solidification morphologies of the Ti5Si3 primary phases. With increasing the Ni content of the elemental powder blends, grain size and volume fraction of the Ti5Si3 primary phases decrease significantly. Microhardness values of the PTA clad intermetallic composite coatings are remarkable influenced by the volume fraction of the Ti5Si3 primary phases. The higher the volume fraction of the Ti5Si3 primary phases, the higher the microhardness value of the PTA cladding coatings. Room temperature dry sliding wear properties of the PTA cladding coatings are significantly affected by both the solidification morphologies and volume fraction of the Ti5Si3 primary phases.