PROCESSING AND CHARACTERIZATION OF GLASS-FILLED POLYAMIDE COMPOSITE COATINGS

Glass-polyamide composite coatings have been successfully plasma spray ed on to steel by simultaneous injection of glass and polyamide partic les into the plasma jet. The deposition conditions were selected such that the polyamide melts in the jet in order to provide the matrix, wh ereas the glass remains solid to avoid overheating the polymer. The de position efficiency of glass is significantly less than that of polyam ide, particularly in the initial stages of spraying, because the solid glass particles deform elastically on impact with the substrate and r ebound, whereas the kinetic energy of the molten polyamide particles i s absorbed by viscous flow. The presence of the glass filler reduces t he wear rate of polyamide by an order of magnitude because of its load -supporting action and reduction of adhesive and abrasive wear. Howeve r, there is a minimum in wear rate at a glass filler content of 50 wt% , because higher glass contents adversely affect wear performance by r educing the fracture toughness. The results also show that refining th e glass particle size provides a considerable reduction in wear rate o f the composite. The first-order theory of adhesive and abrasive wear, in which the wear rate is inversely related to hardness, is shown not to hold for this class of materials.