Nitriding of Titanium and its Alloys

Abstract

Investigations were made on the nitriding process of titanium and its alloys containing 3%Al, 3%Mn, 7%Mn, 3%Fe and 7%Fe, respectively. Nitrided specimens were examined by weight gain, X-ray diffraction, electron beam X-ray microanalysis, microhardness and metallographic techniques. TiN was detected on titanium and its alloys at 1200°C, while ε-TiN and TiN were observed at 1000°C. A case which consisted of nitride film and α-layer was produced on the rim of the specimens. Elongated α grains were observed below the case on the Ti-3%Al alloy nitrided at 1000°C. The hardness gradient, consequently the nitrogen gradient, was remarkable in the α-phase layer, but not detected in the elongated α grains. In nitrided specimens of Ti-Mn and Ti-Fe alloys, the enrichment of manganese and iron was observed in the β-phase next to the α⁄β interface, but such an enrichment of alminum in the Ti-3%Al alloy was observed in the vicinity of the nitride film/α-phase interface.