Plasma-assisted surface hardening of dual two-phase intermetallic alloy composed of Ni3X type structures

A dual two-phase intermetallic alloy composed of Ni3Al (L12) and Ni3V (D022) was plasma-nitrided (PN) or -carburized (PC) in dependence of processing temperature and time. The surface layers of nitrided or carburized alloy were characterized by micro-hardness measurement, scanning electron microscopy, electron probe micro-analysis and X-ray diffraction analysis. The maximum surface hardness of the alloy was obtained by nitriding at around 850 K and by carburizing at 1025 K, and little decreased up to a high temperature with increasing temperature. The XRD analysis revealed that vanadium nitrides (VN) and vanadium carbides (VC) were formed in the surface layer of the nitrided and carburized alloy, respectively; suggesting that the enhanced surface hardness is attributed to the dispersion hardening due to the nitrides and carbides.