Stress Field Simulation and its Experimental Verification of Carburizing-Quenching Process Performed on 18CrNiMo7-6 Steel

Abstract

The carburizing and quenching process of 18CrNiMo7-6 steel was performed through simulation methods and experiments. The study was carried out to accurately predict the residual stress distribution of carburized samples after the quenching process. The stress and retained-austenite amount were measured via X-ray diffraction. Similarly, the carbon content was determined using a carbon sulfur analyzer, respectively. A detailed model with the coupling of thermal, metallic, and mechanical fields was built to predict the evolution of the stress field during the quenching process. The carburized “thoroughly” specimens at different carbon potentials were used to obtain the required mechanical property parameters and dilatometric parameters for FEM simulation. According to the results, the martensite transformation kinetic parameters α value of 18CrNiMo7-6 alloy steel should be 0.0202. With the increase of carbon content, the changing trend of the transformation plasticity coefficient K appeared as a 'tick' shape. A compressive residual stress field was generated at the carburized layer surface after the quenching process, and the maximum value of 340 MPa occurred at ~ 0.9 mm below the surface. The carbon profile and residual stress fields predicted from the FEM simulation corresponded closely to the experimentally determined results.