EROSION RESISTANCE OF DIAMOND COATINGS

Preliminary solid particle erosion testing of 10 mum thick diamond fil ms on silicon substrates showed excellent erosion resistance. The appl ication of diamond coatings to materials that are commonly used in ero sive environments should result in significant improvement over other erosion-resistant coatings. Diamond films were applied to silicon, tun gsten and Ti-6Al-4V using a high-pressure microwave-assisted plasma de position system and were determined to have a high degree of sp3 bondi ng using Raman spectroscopy. Erosion tests were performed on diamond-c oated silicon, tungsten and Ti-6Al-4V, as well as on uncoated substrat es and alternative coatings. The erosion resistances of the target mat erials were compared using volume loss versus erodent mass plots and s teady-state erosion-rate data. Diamond-coated silicon showed the highe st erosion resistance. Diamond-coated Ti-6Al-4V also showed high erosi on resistance when compared with uncoated materials. Erosion mechanism s were identified by examination of eroded surfaces using scanning ele ctron microscopy. Diamond coatings on Ti-6Al-4V substrates fail by del amination of the coating from the substrate. This is believed to be a result of high residual stresses and stress concentrations at the coat ing-substrate interface. Diamond coatings on silicon and tungsten subs trates are gradually removed by a brittle erosion process.