The use of laser radiation to improve the surface properties of titanium has been the subject of a number of
investigations.1-1o Ayers and co-workers1-s injected hard particles of TiC and WC into laser surface melted zones on various substrates and demonstrated that wear resistance was improved. For example, Ti-6AI-4V (wt-%) alloy injected with 30-50 vol.-%TiC had a hardness of 450 HV; the coefficient of friction decreased when the TiC content wa~ increased, reaching a minimum at 50 vol.-%TiC (Ref. 5). The high reactivity of titanium with gases such as nitrogen and oxygen led to the development of a new method of improving the wear resistance6-1o involving laser surface melting in a nitrogen atmosphere. A pulsed Nd- YAG laser and a CW CO2 laser* having powers of 200 W and 2-5 kW, respectively, were used. In one report, for example, the hardness was increased from 200 to 700 HV in a single pass using a CW CO2 laser and this increase was