SURFACE HARDENING OF Ni ALLOYS BY MEANS OF THE PLASMA ION NITRIDING (PIN) PROCESS (REPORT 1).

The probability of surface hardening by means of the Plasma Ion Nitriding (PIN) process was investigated for pure nickel and commercially used Ni alloys under the conditions of having a nitriding temperature 773-1073 K and a nitriding time of up to 32. 4ks in a N//2 plus H//2 mixed gas atmosphere of 800Pa. Marked surface hardening of more than Hv500 was observed at a nitriding temperature 733-1073 K for Inconel 600, 625, 713C and Udimet 500, which contain chromium, and Hastelloy B, which contains molybdenum. On the other hand, Permalloy, which contains iron, was slightly hardened, and pure Ni and Monel were not hardened. It was considered that the hardness increase in the PIN process of Ni alloys was due to a nonuniform microstrain caused by the precipitation of such nitrides in a nitrided layer.