The wear resistance of pure titanium is poor and as a result its application under severe wear conditions is highly restricted. To improve the wear resistance of pure titanium, its surface hardness was improved in this study by the application of laser cladding with TiC powder of 3-10 µm particle size. This treatment was performed using YAG fiber laser at 1700, 2000, 2200 and 2800 W, speed of 4 mm/s and argon as a shielding gas. The powder layers of 1 and 0.5 mm thick were replaced on the specimens for one and two passes. In these cases, surface cladding layers of Ti/TiC composite were produced. The increase of processing power caused increase in the depths of the cladding layer and heat-affected zones. Hardened zones of depths ranging from 0.7 to 1.2 mm were achieved by increasing the processing power from 1700 to 2800 W. The surface hardness of the cladded layer was improved as almost 13 times as that of the substrate in the case of 1700 W. The microhardness of the heat-affected zone was also increased. The improvement in hardness was decreased in the cases of two passes and the specimens cladded with powder layer were replaced with 0.5 mm thickness.

Titanium and its alloys are extensively used in aircraft (Tian et al., 2005; Baogang et al., 2008; Weifu et al., 2008; and Zimmermann et al., 2012), marine and chemical industries due to their low density, high weight-to-strength ratio, excellent resistance for corrosion and oxidation especially at high-temperatures (Tian et al., 2005; Baogang et al., 2008; Hamad et al., 2010; and Zimmermann et al., 2012). However, the application of titanium alloys under severe wear and friction conditions is highly restricted due to their poor tribological properties (Tian et al., 2005). Replacing the worn structural member with a new one increases the cost (Weifu et al., 2008). In addition, titanium and some of its alloys are commonly used as medical implants (Tian et al., 2005) but their failure occurs by wear and corrosion-fatigue. The conventional surface hardening (chemical heat treatment) such as nitriding, carburizing, boriding and thermal spray coatings can deform the workpiece and the treatments take long time (Tian et al., 2005). Also, a limited bond strength between the coating and the substrate results in cases of thermal spray coatings (Tian et al., 2005). These problems can be eliminated and the wear and corrosion resistance of titanium and its alloys can be enhanced by the application of laser surface treatments such as melting and cladding (Tian et al., 2005). Pei and Hosson (2000) reported that the surface of the specimens treated by laser surface melting is modified mainly by the homogenization and refinement of the microstructure. In addition, different precipitates may be formed in some alloys and the supersaturation of some phases increased due to nonequilibrium solidification. However, these modifications are limited, because the composition of the melted layer is the same with respect to the substrate (Pei and Hosson, 2000). In laser cladding, the cladding material is melted and metallurgically bonded with the substrate. As a result, the wear, corrosion and fatigue properties of the parts can be improved. The main advantages of this process over the traditional cladding ones are high deposition rates, low dilution of the substrate, high cooling rates and low distortion (Jian et al., 2007). However, it causes some residual stresses which can lead to some cracks, especially at multiple overlap tracks (Robinson et al., 1996; and Jian et al., 2007).

TiC is highly compatible with titanium because it possesses both metallic and refractory properties (Rasheedat et al., 2013). To obtain clad zone of large depth for long service life, the treatment should be tried at high processing power. Therefore, the present paper is to study the applicability of YAG fiber laser with high power (1700-2800 W) in cladding of Commercially Pure Titanium (CPTi) with TiC.

Mechanical Engineering Journal, Commercially Pure Titanium (CPTi), Wear resistance, Laser cladding, TiC, Surface composite materials, Surface hardness.