窒化物生成元素を添加したＮｉ２元および３元合金の窒化層の腐食挙動 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６報

Abstract

In order to investigate the corrosion properties of Ni alloys after nitriding treatment, tentative Ni binary alloys of Ni-7 wt%Ti, -15 wt%V, -10 wt%Nb, -20 wt%Cr and -30 wt%Cr and Ni ternary alloys of Ni-7 wt%Ti-2 wt% (V, Nb, Ta, Cr, Mo or Al) and Ni-20 wt%Cr-2 wt% (Ti, V, Nb, Ta, Mo or Al) were nitrided by means of PIN process under the condition of 873 K (823 K at Ni-30 wt%Cr), 10.8 ks, N2+H2 mixed gas atmosphere of 800 Pa. Corrosion properties of tentative Ni alloys were determined in an acid solution (30°C, 5%H2SO4) by means of potentiodynamic polarization methode. Pure nickel and austenitic stainless steel; SUS304 were also used as reference materials.Tentative Ni alloys showed better corrosion resistance then pure nickel before PIN treatment. PIN treatment resulted in a slight deterioration of corrosion resistance of tentative Ni alloys. Comparison of corrosion resistance of Ni alloys and SUS304 after PIN treatment, deterioration of corrosion resistance of Ni alloys were slighter than SUS304. Pitting and intergranular corrosion were observed in nitrided Ni binary alloys excepted Ni-Cr alloys and Ni-7 wt%Ti-X ternary alloys. Separation of nitrided layer occured in nitrided Ni-Cr binary alloys.Taking into consideration of corrosion properties of each tentative Ni binary and ternary alloys after PIN treatment and hardening behavior of their alloys by PIN treatment, it seemed that Ni-7 wt% Ti binary alloys and Ni-7 wt%-X and Ni-20 wt%Cr-X ternary alloys were most benefitial Ni alloys for using after PIN treatment.