Laser transformation hardening of steel: effects of beam mode, beam size, and composition

Laser transformation hardening experiments have been carried out on three m odel steel alloys of nominal composition Fe-0.4C, Fe-0.4C-1.0Mn, and Fe-0.4 C-1.0Si (wt-%). A 1 kW continuous wave laser with a near. Gaussian beam and a 5 kW continuous wave laser fitted with a beam integration device have be en employed. Thus, it has proved possible to isolate the effects of alloy c hemistry and beam mode on the kinetics of the hardening process. The dimens ions of the hardened zones have been characterised and the results compared with calculations made using process models. It is shown that the results from experiment and theory are in broad agreement. Hardened zones resulting from the uniform source had a larger width/depth ratio than those resultin g from the Gaussian source, although the effect was not as enhanced as sugg ested by theory. A comparison of the Fe-C, Fe-C-Mn, and Fe-C-Si specimens r evealed that manganese and silicon increased the width of the transformed z one, and that this effect was more significant at higher processing speeds. MST/3963.