The Scraping Test and Adhesion Measurements of Diamond and Nickel Electroless Coatings

The scraping method, and a tester using the scraping method, have been introduced and applied to evaluate the effects of deposition processes and surface treatments on the adhesion of nickel electroless coatings and diamond coatings. An energy description for the adhesion based upon the scraping test and an elastic-plastic crack propagation mode for the separation of the coating/substrate have also been introduced to illustrate the energy characteristic of the adhesion and the elastic-plastic fracture mechanics foundation of the scraping test. We have also discussed the influence of coating thickness on adhesion for NiP coatings deposited on carbon tool steel substrates, and suggested the scraping energy as the description for the adhesion strength obtained from the scraping test. It was found that the adhesion of the NiP/steel substrate reduced with the increase of the thickness of the NiP coatings until the adhesion limit reached the critical coating thickness. It was also found that the adhesion of diamond coatings was greatly affected by the temperature of the hot filament, the treatments of the substrate surface, and the composition of the etching solutions.