Laser transformation hardening of Ti–6Al–4V in solid state with accompanying kinetic model

Abstract

Laser transformation hardening in the solid state is shown to successfully provide a surface hardness increase of almost 40% for Ti–6Al–4V with a case depth over 2.5 mm while reducing surface damage. This was completed by testing a matrix of four conditions using a direct diode laser, varying the power and the travel speed, followed by a mechanical and microstructural analysis of the hardness development. A kinetic model was developed to predict these changes by explaining the amount of α that transforms to β upon heating and the fraction of martensitic α′ that forms with natural quenching. The model matched the experimental results reasonably well with the major separation due to the poor hardenability of Ti–6Al–4V.