Studies on laser surface melting of tool steel - Part II: Mechanical properties of the surface

Abstract

In the present study, the effect of laser surface melting using different proportions of argon and nitrogen as shrouding atmosphere on microhardness and wear resistance properties of a low alloy high carbon tool steel (SAE 52100 steel) has been undertaken. Laser surface melting in argon (Ar) atmosphere significantly refined the microstructure (grain size) with the presence of carbides (both iron and chromium) and martensites and improved microhardness (350-500 VHN) as compared to as-received SAE 52100 steel (280 VHN). Laser surface melting in 100% N₂ atmosphere led to formation of thin nitride (consisting of Fe₄N and Fe₂N and Cr₂N) layer with improved microhardness to as high as 1050 VHN. Wear studies showed a significant enhancement in wear resistance against hardened steel ball, a maximum improvement was achieved when lased using 100% N₂. The mechanism of wear was studied in details.