Characterization of elastic-plastic properties of surface-modified layers introduced by carburizing

Abstract

The mechanical performance of surface-modified layers is important during mechanical-component service. A simpler expression to characterize the carbon content of the surface-modified layers was proposed for alloy steel after carburizing. The tensile test method was used to determine the elastic–plastic properties of the surface-modified layers of the 18CrNiMo7-6 carburized alloy. The hardness of all tensile test specimens was determined and the relationship with the carbon content was given. The elastic modulus, yield strength and hardening exponents were obtained for the surface-modified layer from the tensile test and stress–strain curves. The elastic modulus does not change with depth, whereas the yield strength and hardening exponent decreased gradually along the depth and were almost correlated with the carbon distribution. The hardening exponent model of the surface-modified layer was given as an exponential function. The relationship between elastic modulus, yield strength, hardening exponent and hardness agrees broadly with the modified expanding cavity model for the surface-modified layer of 18CrNiMo7-6 carburized alloy.