Microstructures, Corrosion Resistance and Mechanical Properties of TiC-Ti-W Sintered Hard Alloy Affected by the Additional Amounts of Mo

Abstract

The 47.4 vol% TiC-44.2 vol% Ti- 8.4 vol% W alloy was stronger than TiC-Ti-Mo alloy because the TiC particle size was smaller than that of the TiC-Ti-Mo alloy, however its corrosion resistance was inferior to the TiC-Ti-Mo alloy. The additive element for maintaining high strength needs to have the effect of forming βTi phase that promotes sintering and reducing the diameter of TiC particles. Mo and V are candidate for additive elements. Mo improves corrosion resistance more than V does. Therefore, a part of W was replaced with Mo, and the mechanical properties and corrosion resistance were investigated. It was found that 20 vol% Mo / (Mo + W)-added alloy excels in strength and corrosion resistance. The alloy sintered at 1573 K and HIP-treated showed the highest bending strength of 0.82 GPa with the hardness of HRC 68.2. It was confirmed that there is a correlation between the fracture origin size that caused the fracture of these test pieces and the fracture stress acting on the fracture. The high strength was obtained due to two effects: the alloy matrix strength was improved by the refinement of the microstructure, and the fracture origin size was reduced by the HIP treatment.