Laser surface hardening: a review

Laser surface hardening (LSH) is one of the most widely used surface hardening process which can be applied to almost the whole range of metallic materials in today's applications. Laser beam is focused to the localised region for hardening the required portion of the material. High intensity laser radiation is involved for heating the surface of steel into the austenitic region. Steep temperature gradient arises, due to high rates of heat transformation that results in instant cooling by conduction. It causes the phase conversion from austenite to martensite without the need for external quenching. Among various types of lasers, CO2, Nd: YAG and diode lasers are the widely used lasers for hardening in industries. This review paper is a summary of the basic fundamentals of laser hardening, figuring some of its benefits compared with conventional hardening technique. The works published by various researchers by experimentation and by numerical approach are presented.