THE MICROSTRUCTURE AND GALLING WEAR OF A LASER-MELTED COBALT-BASE HARDFACING ALLOY

A carbon dioxide laser was used to modify the surface of a Stellite 156 weld overlay that had been deposited using a plasma transferred arc. Conditions were identified that resulted in a crack-free surface. The modified surfaces were characterized using optical microscopy, microhardness measurements and scanning electron microscopy-energy-dispersive X-ray analysis. Galling wear resistance was determined using a pin-on-plate test. Pre- and post-test surface roughness values were determined with a profilometer. Laser-induced melting led to a significant increase in microhardness, a significant reduction in grain size and a more uniform distribution of alloying elements in the cobalt-rich matrix and the carbide precipitates. However, the galling wear resistance of the laser-melted specimens was unchanged from that measured on untreated specimens.