CVD Diamond Coating for Erosion Protection at Elevated Temperatures

Small solid particles entrained in a gas-fluid turbomachinery flow can cause degradation of the component surfaces containing the flow by erosion and corrosion processes. As diamond is the hardest known material, much work has been done to use polycrystalline diamond (PCD) as a protective coating on parts operating in a hostile and abrasive environment. Little attention is given in the literature to the high-temperature erosion behavior of chemical vapor deposition (CVD) diamond on different substrates. The objectives of this research were to develop CVD diamond erosion barriers for surface protection of cemented tungsten carbide at high temperatures and to study the erosion behavior of the coatings. Microwave plasma chemical vapor deposition (MPCVD) was used to apply diamond films on WC-6%Co. The erosion behavior of the coated specimens was investigated experimentally by exposing them to abrasive particle-laden flow in a high-temperature wind tunnel. The obtained results show the effects of impingement angle, temperature, and particle dose on the erosion rate. The data demonstrate that uncoated substrates suffer 6–7 times higher wear compared to diamond-coated samples at elevated temperatures up to 538 °C when exposed to alumina particle flow. This study indicates that polycrystalline diamond is emerging as a promising erosion protective coating for high-temperature applications.