The adhesion of hot-filament CVD diamond films on AISI type 316 austenitic stainless steel

Steel ball indentation and scratch adhesion testing of hot filament chemical vapour deposited diamond films onto AISI type 316 austenitic stainless steel substrates using two different interlayer systems, namely chromium nitride and borided steel, have been investigated. In order to compare the adhesion of these films with that of a well-known and strongly adherent system, detailed adhesion tests were performed on diamond films grown on molybdenum substrates as well. Scanning electron microscopy analysis of various indented regions on the diamond-coated steel and molybdenum samples in combination with the measurement of the acoustic emission signals during loading, indicate that the adhesion of the coatings on the stainless steel substrates with the CrN interlayer is comparable and only slightly less than that of the strongly adhering diamond films on the molybdenum samples. The critical load value derived from the acoustic emission signals at which partial delammation of the diamond films is first observed, is significantly lower for the diamond-coated steel with the boride interlayer than that obtained with the CrN interlayer for the present deposition conditions used. The steel ball indentation tests also show that the hardness and thickness of the interlayer have a strong effect on the penetration depths of the indents. Scratch tests performed on the diamond coated stainless steel specimens with the boride interlayer show no significant coating failure for loads up to 80 N. (C) 2003 Elsevier B.V. All rights reserved.