Laser surface alloying of silicon into aluminum casting alloys

Aluminum alloys that are easily castable tend to have lower silicon content , and hence, lower wear resistance. The use of laser surface alloying to im prove the surface wear resistance of 319 and 320 aluminum alloys was examin ed. A silicon layer was painted onto the surface to be treated. A high powe r pulsed Nd:yttrium-aluminum-garnet laser with fiber-optic beam delivery wa s used to carry out the laser surface treatment to enhance the silicon cont ent and produce a very fine silicon-rich phase. One advantage of using a pu lsed laser beam to carry out the surface alloying is it provides a vigorous turbulence in the molten pool and enhances the dissolution of the fine sil icon into the molten bath and its dispersal in a short process time. Proces s parameters were varied to obtain smooth single treated tracks and minimiz e the surface roughness from overlap of the treated tracks. Our goal is to take advantage of the vigorous turbulence characteristic of the pulsed beam to obtain desired microstructure of laser-alloyed layers, and at the same time to employ the pulse parameters that mimic continuous wave operation as closely as possible to produce the smooth surface. The surface-alloyed lay er was characterized and the silicon content and microhardness profile were determined. (C) 2000 Laser Institute of America. [S1042-346X(00)00503-9].