抄録
In order to investigate the influence of alloying elements, low-carbon alloy steels containing Mo, Nb, V and Cr were ion-nitrided at 823K for 2 and 4h in a 50%N2-50%H2 gas mixture at 800Pa. Samples of the ion-nirtided low-carbon alloy steels were subjected to hardness test, microscopic examination and X-ray diffraction analysis. The following conclusions were reached. Ion-nitriding produced a markedly hardened surface layer on samples containig, Nb, V ans Cr. There was little increase in hardness in samples containing Mo and samples of plain low-carbon steel. Sectional hardness distributions of the nitrided steels showed characteristic shapes attributable to the alloyig elements in the steels. Vanadium and niobium steels showed, respectively, 2 and 3 plateaus in thier hardness distribution curves. A white layer of ε-Fe2-3N nitride was formed on the surface of nitrided samples, and characteristic nitriding layer was formed beneath that nitride layer. The large increase in the hardness of the nitriding layer is attributed to precipitation of the very fine alloy nitrides accompanying the very high levels of precipitation strain.
