Abstract
The property of the ion-softnitriding layer formed on S15C steel and the wear resistance of the ion-softnitrided S15C steel under a dry sliding condition were investigated. S15C steel was ion-softnitrided in N2–H2–CH4 gas mixtures of various compositions at 823 K for 14.4 ks under a pressure of 6.67×102 Pa. With increasing CH4 gas content in the atmosphere, the compound layer becomes thinner and the diffusion layer also becomes shallower or does not form. The thick compound layer is formed in the gas compositions of [CH4%]<1/12[N2%]+1/3. The phase composition of the compound layer is affected by the CH4 gas content in the atmosphere and ε-Fe2−3(CN) phase is easily formed by the addition of CH4 gas. The increase in CH4 gas content brings about the formation of Fe3C and finally results in sooting. The ion-softnitriding markedly improves the wear resistance of steel and is more effective for the wear resistance at high speeds under high loads than the ion-nitriding.
