Wear and corrosion behavior of laser surface engineered AISI H13 hot working tool steel

The present study reports the effect of laser parameters on the microstructure, and consequently, the wear resistance of laser surface engineered (hardening and melting) AISI H13 tool steel (in hardened and tempered condition) substrate. The microstructure of the laser surface hardened zone consists of ultrafine mixed carbides (M23C6, M7C3, MC or M2C) dispersed between martensite laths. On the other hand, a laser surface melted microstructure comprises retained austenite, martensite, transformed ledeburite and fine carbides precipitated in the inter-dendritic zone. Microhardness of the laser surface engineered zone is significantly enhanced to as high as 670-810 VHN as compared to 480-500 VHN of the as received quenched and tempered substrate and decreases along vertical depth from the surface until a narrow soft zone at the interface with a typical hardness of 440 VHN. Laser surface melting yields a higher hardness level (770 +/- 10 VHN) as compared to that after laser surface hardening (660 +/- 10 VHN). Wear resistance of laser surface engineered samples (evaluated both by ball-on-disk and fretting wear testing equipments) shows a significant improvement as compared to that in hardened and tempered condition. Due to an increased hardness, surface melting shows superior resistance to wear both under fretting as well as ball on disk wear testing conditions. A marginal improvement in corrosion resistance was also recorded in laser surface engineered samples due to microstructural/compositional homogenization introduced by laser surface engineering. (C) 2014 Elsevier B.V. All rights reserved.