Microstructure and fatigue properties of 17Cr2Ni2MoVNb gear steel after gas carburizing and low-pressure carburizing

• Microstructure and fatigue properties of low-pressure carburized 17Cr2Ni2MoVNb steel. • The effect of gas carburizing (GC) was compared with low-pressure carburized (LPC). • Fewer carbides and a higher fraction of RA were in the LPC carburized layer. • The fatigue limit of both LPC and GC specimens was about 980 MPa. • The fatigue lives of the LPC specimens were longer under the high cyclic stresses. In this work, the microstructure and fatigue properties of the 17Cr2Ni2MoVNb gear steel after gas carburizing (GC) and low-pressure carburizing (LPC) were comparatively evaluated. The results showed that fewer carbides and a higher fraction of retained austenite (RA) were found in the carburized layer of the LPC specimens, as a result of the different quenching temperature. Rotating bending fatigue tests revealed that both the LPC and GC specimens had a fatigue limit of 980 MPa. Compared with the GC specimens, the LPC specimens had significantly higher fatigue strengths at a specific number of cycles under high cyclic stresses.