Microstructure and mechanical property of electropulsing tempered ultrafine grained 42CrMo steel

Abstract Microstructure and mechanical property of 42CrMo steel after electropulsing (EP) treatment were studied. The average prior austenite grains (PAGs) size was refined to 2.9 μm after EP austenitization, compared with conventional austenitization. EBSD test results indicated the size of sub-grains with high angle boundaries was refined from 1.53 μm to 0.53 μm. The quenched 42CrMo steel with ultrafine PAGs was tempered by EP with peak temperatures ranging from 524–670 °C. Carbides precipitated during EP tempering within the total duration less than 20s. The size of carbides was refined. Combined with grain refinement strengthening and higher precipitation strengthening effects, the strength of EP treated 42CrMo steel was dramatically improved. The effects of PAGs ultra-refinement on martensitic structures were discussed. And the reasons for carbides refinement were analyzed. One reasonable reason was due to the PAGs ultra-refinement. Another reason should be attributed to the athermal effect of high density pulse current.