Heat-resistant alloys are superior to stainless steel or heat-resistant steel in high-temperature strength and heat-resistance, and therefore are used in various industrial applications.

Typical heat-resistant alloys include nickel-based alloys such as Inconel and Waspaloy, which are used in aircraft engine turbine parts, shafts, cases and generation turbine parts.

While they are known for excellent high-temperature strength and heat resistance, they are also known as significantly difficult-to-process metals because hardening is more likely to occur and dispersing of the heat generated by cutting is slower as its thermal conductivity is smaller than that of carbon steel and the like that it can impact manufacturing cost.

Meanwhile, in order to improve fuel consumption rate (SPC: Specific Fuel Consumption), aircraft engine manufactures have been developing various products such as high-temperatures, and high-efficient combustors with low-environmental impact. Apparently, it is expected that the next-generation heat-resistant alloys will become even more difficult to process.

In this paper we will introduce some cutting tool materials for handling those alloys as well as new cutting materials we have developed to support machining them.

To obtain a significantly higher Young’s modulus than conventional wrought steels, the improvement of the sintered density was necessary for low-alloyed sintered steels containing 15 vol% or more TiB₂. In this study, the effect of boride powders as the small amount additives on the sintered density and the Young’s modulus of TiB₂ reinforced low-alloyed sintered steels was investigated.

A small amount addition of ZrB₂ powder was suitable to increase the sintered density of low-alloyed sintered steels containing 15 vol% or more TiB₂, because of promoting the infiltration of the liquid phase formed during sintering into the agglomerates of TiB₂ particles. As a result, the high sintered density equivalent to 97% of pore free density and the high Young’s modulus of 300 GPa equivalent to 1.5 times that of conventional wrought steels were achieved when the content of TiB₂ was 40 vol%.

The mechanical properties of selective laser melting (SLM) titanium (Ti) materials can be enhanced by solid solution with oxygen (O) element. However, the microstructure changes and their relationship with mechanical properties of SLM Ti materials have not been clearly revealed in the view point of the dissolved oxygen amount. In this study, we investigated the effect of oxygen element on the microstructures and mechanical properties of SLM α-Ti materials. Furthermore, the strengthening mechanism of SLM Ti materials was also investigated quantitatively. The SLM Ti material without additional oxygen consisted of coarse grains, whereas the SLM materials with 0.35 ~ 0.89 mass% O consisted of acicular α-Ti grains. As the oxygen amount increased, tensile strength was increased while maintaining a high elongation at break. The tensile strength of the 0.89 mass% O material increased by 764 MPa compared to the material without additional oxygen. The strengthening mechanism of SLM Ti-O alloys was quantitatively clarified to be oxygen solid solution and grain refinement strengthening.