EVALUATION OF THERMALLY-SPRAYED CERAMIC COATINGS USING A NOVEL BALL-ON-INCLINED PLANE SCRATCH METHOD

A ball-on-inclined plane scratch test method has been developed to det ermine the materials responses to stresses on thermally-sprayed cerami c coatings. Material properties such as the critical damage load, dama ge patterns of the scratched surface and subsurface crack patterns are evaluated. Results show that when the applied load is below the criti cal value, then is no subsurface damage but plastic deformation occurs locally on the surface. Beyond the critical load, high velocity oxyge n fuel (HVOF) sprayed Al2O3 coatings exhibit plastic deformation on th e scratched surface and subsurface cracks propagating in the direction s parallel to and at an angle to the sliding surface. In the case of a plasma-sprayed ZrO2 coating, beyond the critical load, cracks initiat e at the surface and propagate into the subsurface at an angle about 3 0 degrees to the sliding surface. (C) 1998 Elsevier Science S.A. All r ights reserved.