Material for high-speed airframe are typically selected such that high ablation resistance is maintained on the material surface while high pull-strength is maintained inside the material. However, in case of application to extremely severe condition, the material should have better mechanical properties. Thus, heat treatment or surface treatment is utilized to improve the mechanical properties. This study is conducted as a preliminary research to improve the mechanical properties of vehicle material considering the frictional heat produced during high-speed vehicle is in motion. In this study, Inconel 625 alloy, widely used material for the application of high-speed air vehicle, is ion nitriding processed and then mechanical property test and wear test on this material are conducted consequently. As results, mechanical properties such as tensile strength, yield strength and hardness are increased, and also wear rate is increased at particular condition.

This study has been performed on the full density sintering of Fe nanopowder and the surface hardening by plasma ion nitriding. The Fe sintered part was fabricated by pressureless sintering of the Fe nanopowder at in which the nanopowder agglomerates were controlled to have 0.5-5 sized agglomerates with 150 nm Fe nanopowders. The green compact with 46% theoretical density(T.D.) showed a homogeneous microstructure with fine pores below 1 . After sintering, the powder compact underwent full densification process with above 98%T.D. and uniform nanoscale microstructure. This enhanced sintering is thought to be basically due to the homogeneous microstructure in the green compact in which the large pores are removed by wet-milling. Plasma ion nitriding of the sintered part resulted in the formation of '- equilibrium phase with about 12 thickness, leading to the surface hardening of the sintered Fe part. The surface hardness was remarkably increased from 176 for the matrix to 365 .