Experimental study - Control of defects during laser surface alloying

Laser surface alloying is a new and promising technique for generating surf ace alloys having a wide range of favourable properties. The process involv es altering the surfaces of inexpensive substrates by adding small quantiti es of alloying elements to a pool of molten metal produced by local melting using the intense heat of a laser. Certain defects such as cracks, porosit y, surface roughness, compositional inhomogeneity, and excessive dilution h ave been observed during laser alloying (pulsed Nd:YAG laser) with chromium on mild steel, and with molybdenum and Ni-Mo on stainless steel. Specific deterioration in surface properties has been observed and discussed and the techniques utilised to control such defects have been outlined. (C) 1999 I oM Communications Ltd.