非鉄金属材料のプラズマイオン窒化法による表面改質（第４報） プラズマイオン窒化したＮｉ２元合金の窒化層の微細構造と硬化機構

Abstract

In order to investigate the hardening mechanism of Ni alloys by nitriding treatment, tentative Ni binary alloys of Ni-7wt%Ti, Ni-15wt%V, Ni-10wt%Nb and Ni-30wt%Cr were intrided by plasma ion nitriding (PIN) process under various conditions of nitriding temperature from 673 to 1073K and nitriding time at 10, 8ks in N2+H2 mixed gas atmosphere of 800Pa.Hardness of the nitrided layer was increased with decrease of nitriding temperature. From the X-ray diffraction analysis and transmission electron microscopy, it was considered that the hardening mechansim of Ni alloys by PIN process was due mainly to the lattice strain of the matrix of nitrided layer caused by dispersive precipitation of metastable nitrides of each alloying element. A lower hardness of the nitrided layer at higher nitriding temperature was owing to the decrease of lattice strain by coarsening of equilibrium nitride particles.