Improving stress corrosion resistance and wear resistance of austenitic hot-stamping die steels via synergistic effects of shot peening and plasma nitriding

Abstract

In this work, the effects of plasma nitriding, shot peening and their combination on the high-temperature wear resistance and stress corrosion resistance of an austenitic hot-stamping die steel were investigated. The results showed that the nitrided layer consisted of a single expanded austenite after nitriding at 560 °C for 4 h. Shot-peening pretreatment improved the surface hardness and depth of nitrided layer by 29.4 % and 36.4 % compared with the nitrided-only samples. This could be attributed to an increase in dislocation density, sub-crystal refinement, precipitation of nanoscale carbides and high strain of carbides and slip bands. Nitriding increased the stress corrosion resistance and high-temperature wear resistance of materials. Samples nitrided after shot peening showed the greatest wear and corrosion resistance. Besides, the introduction of residual compressive stresses in the nitrided layer by shot peening also improved wear and corrosion resistance to some extent.