Improvement of cavitation erosion resistance of AISI 316 stainless steel by laser surface alloying using fine WC powder

Fine WC powder of approximately 1 mum size was employed as a convenient source of tungsten and carbon in the laser surface alloying of AISI 316 stainless steel for improving the cavitation erosion resistance. A slurry containing WC powder was preplaced on the substrate by pasting and processed with a high-power CW Nd:YAG laser to achieve surface alloying. The composition and microstructure of the alloyed layer and the phases formed were investigated by energy-dispersive X-ray spectroscopy, optical microscopy, scanning electron microscopy, and X-ray diffractometry, respectively. The cavitation erosion behavior of the laser surface-alloyed samples in 3.5% NaCl solution was studied with a vibratory cavitation erosion tester. The microhardness of the alloyed layer increases with the total W content in the layer. By employing proper processing parameters, an alloyed layer that is hard but not too brittle can be formed, with a cavitation erosion resistance that may reach more than 30 times that of the as-received 316. The improvement in cavitation erosion resistance may be attributed to the increase of Win solid solution and to the precipitation of dendritic carbides, both resulting from the dissociation of the fine WC powder during laser processing. (C) 2002 Elsevier Science B.V. All rights reserved.