Phase changes in a laser-alloyed Fe-5Cr steel

Abstract

Laser surface alloying is a relatively new method to modify metal surfaces. A suitably applied metal coating and an underlying metal substrate are rapidly melted by a high power, continuous laser beam. The resultant melting, mixing and rapid solidification can be controlled to form an alloyed fusion zone at the surface with the desired mechanical properties.In this work, Ni-Cr and Ni-Cr-WC metal powders were thermally deposited on a Fe-5Cr steel. Coating parameters were adjusted to achieve desired coating thicknesses. Laser processing was carried out with a continuous CO2 laser beam capable of power densities up to 108 watts/sq.cm. to alloy the metal powder with the base material. Power density, scan rate, spot size and other parameters were all controlled to produce penetration depths of up to 850μm (Table 1). Interpass steps were adjusted to produce both overlapping and discrete fusion zones.