Abstract
A commercially available scratch tester was used to study the response of samples of high speed steel, coated with WC(Co) by d.c. diode and r.f. magnetron sputtering, to the scratch test. The critical load, mode of coating removal and acoustic signals are discussed. The influence of substrate bias, film thickness and substrate hardness was studied. The films deposited by the r.f. sputtering technique show cohesive failure without presenting an extensive spalling, while those obtained by d.c. sputtering reveal characteristics adhesive failure. In some cases good correlation between acoustic emission and the events in the scratch track has been obtained. In the study of substrate bias influence, it was concluded that critical load is interrelated with the hardness and the stress level of the coatings. For a large number of films, critical load increases with the film thickness and the substrate hardness.
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