Comprehensive analysis of fractures, microstructure, and physical and mechanical properties for the evaluation of the crack resistance of medium-carbon Cr–Ni–Mo steel

Resumo

The crack resistance of the 38CrNi3MoV (34NiCrMoV14—5. 35NiCrMoV12—5) tempered steel (at various tempering temperatures) has been estimated based on a comprehensive study of the steel fractures, microstructure, physical, and mechanical properties. Stress-intensity factor K_1C at the apex of the crack is growing continuously with an increase in the tempering temperature from 200 to 620°C. This indicates that K_1C is a structural-sensitive parameter, which depends on the steel microstructure and submicrostructure, the fracture mechanism that occurs under these structural conditions, the internal stress level, and the existence of microdefects and microcracks. The linear correlation dependence is found between the coefficient K_1C and the transverse velocity V_transv. The obtained results reveal that the acoustic method can be used to quickly and efficiently estimate the crack resistance of the thermostrengthened steel without the recourse to labor-consuming mechanical tests and computations of the K_1C value.