Effect of laser surface alloying chromium onto AISI 1018 steel on the fatigue crack growth rate

Abstract

This paper studies the fatigue properties of laser surface alloying chromium onto AISI 1018 steel substrates using 2.5 kW CO 2 continuous lasers. Chromium was electrodeposited onto substrates using conventional electroplating methods. The laser power and traverse speed were varied and their effects were related to the depth, width and solute content of the laser alloying zone. Light microscopy, SEM, EPMA and WDS were employed to characterize the microstructure, fracture surface, chromium and carbon content of the laser surface alloyed specimen, respectively. The microhardness was measured and the fatigue crack growth rate was determined. From the results, it is shown that the early stage of fatigue crack growth rate decreases with increasing melted depth and hardness. The fracture mechanism of the alloyed region is transgranular cleavage fracture, that of the heat affected region is intergranular brittle fracture, and that of the base metal region is transgranular ductile fracture.