This research investigates how laser transformation hardening is improved if the laser beam intensity profile is designed to produce the ideal temperature distribution in the work-piece. The use of diffractive optical kinoform allows the laser beam intensity profile to be highly customized and so optimise the process.
A simple heat flow model was employed to design the beam intensity profile used to generate the temperature distribution in the substrate. Laser transformation hardening experiments were carried out on 0.4% plain carbon steel and 1.5% nickel-chromium-molybdenum low alloy steel using customized laser beam profiles at different incident beam power and scanning rates.
An even surface hardening profile could be accomplished with sharper edges to the laser hardened zone than achieved without complex beam shaping. Optimisation the temperature distribution as the beam passes over the work-piece, allows carbon dissolution to be ensure as the homogenous austenitic transformation can be achieved without surface melting. Judicious design of the beam intensity profile enables successful hardening of steels with coarser carbide formation and higher alloying metal content.