Study of TC4 Titanium Alloy Following Laser-induced Oxygen Diffusion Hardening Under Ambient Atmospheric Conditions
C-J. Chen, M. Zhang, Q-M. Chang and S-C. Zhang
An attempt has been made to determine the influence of oxygen diffusion hardening (ODH) treatment on the microstructure, microhardness and wear behaviour of TC4 alloy. In order to study the effect of ODH treatment, specimens were laser surface melted under ambient atmosphere by different laser input power and scan speed. Characteristic features of the ODH surface were revealed by scanning electron microscope (SEM). The composition of the ODH scales were measured by energy dispersive X-ray analysis (EDX). The microhardness of the ODH scales and the TC4 substrate were identified by microhardness tester. The load was 100 g with a holding time 15 seconds. The wear performance was also evaluated. The surface layer comprises an oxidised rutile TiO2 layer and an underlying oxygen diffusion hardening zone. And it has been found that the surface oxidised layer was adherent to the substrate. The oxygen concentration was gradually decreased from the outmost surface to the substrate. The microhardness was found to be as high as 927 HV, while the substrate had a microhardness of about 340 HV. The laser ODH treated TC4 titanium alloy exhibited significantly improved abrasive wear resistance.
Keywords: TC4 titanium alloy, laser-induced oxygen diffusion hardening, CO2 laser, microstructure, hardness, wear