Surface hardening of S45C by ion-nitriding with a subsidiary cathode

摘要

Ion-nitriding for 545C using Al, Cr and Tisubsidiary cathodes was carried out at 823K for 3hours in anatmosphere of 30%N2-X%H2-Y%Ar mixing gas at 665Pa. Thenitriding layers formed on 545C were characterized by XRD, XPS,microscopic observation and microhardness profile.The surface hardness of 545C was increased with Ar contents upto 20% while N2 was maintained at 30%. Iron nitride phases of ε-Fe2-3N and γ'-Fe4N were found on the surface of 545C ion-nitrided with each subsidiary cathode. From the results of XPSanalysis, Al was found as a combined form with nitrogen in thenitrided layer. Using Al, Cr and Ti subsidiary cathodes, the surfacehardness and thickness of compound layer became higher andthicker than the unused layer one. The surface hardness of S45Cion-nitrided without the subsidiary cathodes was about Hv521. Onthe contrary, the surface hardness of S45C ion-nitrided with Al, Crand Ti subsidiary cathodes were Hv890, Hv734 and Hv667,respectively. These may be due to the sputtered atoms, whichdiffused into the iron nitrides and then increased lattice strain.