Abstract
The probability of surface hardening by means of Plasma-Ion Nitriding (PIN) process was investigated for pure Ni and commercially used Ni alloys under the condition of nitriding temperature from 773 to 1073K and nitriding time up to 32.4ks in N2+H2 atmosphere of 800Pa.
Remarkable surface hardening more than Hv500 was observed for Inconel 600, 625 and 713C and Udimet 500, which were contained Cr element, and Hastelloy B, which was contAlned Mo, at nitriding temperature 773-1073K. On the contrary, Permalloy, which was contAlned Fe, was slightly hardened, and pure Ni and Monel were not hardened.
From the result of X-ray diffraction analysis, CrN for Inconel 600, 625 and 713C and Udimet 500, MoN and Mo2N for Hastelloy B were detected as nitrides together with diffraction peaks from the matrix of nitrided layer and base metal beneath it. Diffraction peaks of these nitrides and matrix of nitrided layer were very broad and the half value width of these peaks had a good relationship with surface hardness, which was linearly increased as the increase of the half value width. Therefore, it was considered that hardness increased by PIN process was due to lattice expansion caused by the precipitation of such nitrides in nitrided layer.
