Tetrahedral amorphous carbon deposited with the pulsed plasma arc-discharge method as a protective coating against solid impingement erosion

The solid impingement erosion resistance of a tetrahedral amorphous carbon (ta-C) coating (sp(3) bonding fraction similar to 80% thickness 20 mu m) was compared to the erosion resistance of stainless steels, WC-Co hard metal, sintered SiC, sintered Al2O3, synthetic ruby (Al2O3, grain size of the order of mm) and a commercial TiN coating. The ta-C coating was deposited by the filtered pulsed plasma are-discharge method on an AISI316L stainless steel sample. Al other materials, except the ta-C and the TiN, were in a bulk form. The experiments revealed that the volume removal rate of bulk materials was 1.5-540 times higher than that of ta-C, depending on the material. The extensive chipping of TiN hindered a meaningful comparison of the measured results to those received from bulk materials. The erasion experiments were performed with a test apparatus, which used pressurized air to accelerate angular Al2O3 particles (60-77 mu m in diameter). The erosion damage was analyzed with a surface profilometer and an optical microscope. The critical thickness for the coating that was able to resist catastrophic delamination under particle exposure, was found to be approximately 1 mu m The extremely low erasion rate of ta-C, when eroded with low values of angle of attack ( similar to 20 degrees), implies that ta-C erodes in a brittle manner. (C) 2000 Elsevier Science S.A. All rights reserved.