Diamond coatings on femtosecond-laser-textured stainless steel 316 surfaces for enhanced adherence

A challenge for directly coating diamond on metallic substrates is the large residual stress near their interfaces due to the large mismatch in the coefficients of thermal expansion (CTEs) that leads to cracking or delamination of the diamond coatings from the substrates. In this work, femtosecond (fs)-laser texturing was applied to fabricate various periodic microgrids on stainless steel (SS) 316 substrates for enhancing the adherence between the SS 316 substrates and the diamond coatings grown using the laser-assisted combustion flame chemical vapor deposition (CVD). Through adjusting the dimensions of the microgrids with different fs scanning parameters, the diamond coatings with a maximum thickness of 19 μm can be grown with quality factors up to 96 % as analyzed by Raman spectroscopy. The corresponding large diamond crystals with an average grain size of 9 μm can be obtained on SS316 substrates by optimizing the fs-laser texturing process. The enhanced adherence between the SS 316 substrates and diamond coatings can be attributed to the stress relief and the improved mechanical bonding. The growth kinetics of the diamond coatings on fs-laser-textured SS 316 substrates were also revealed through the phase constitutions and morphology characteristics. This work is anticipated to provide a new strategy and guidance for the growth of diamond coatings on metallic materials with strong adherence at the interfaces.