Chemical vapor deposition (CVD) has been an important technique significantly impacting the aerospace, cutting tool and other industries, where erosion, wear, and corrosion protection play crucial roles. While in usage for many years, this technique will remain one of the main driving forces behind surface engineering in the next few decades because of its versatility, and ability to be easily scaled up for industrial applications at a reasonable price. The review will provide data demonstrating promising results on CVD coating for erosion protection at elevated temperatures. In addition, conventional and advanced Electron Cyclotron Resonance (RCR) Micro-Wave CVD facilities plus related thin film processing of hard coatings will be discussed.

Small solid particles entrained in a gas-fluid flow can cause degradation of the component surfaces containing the flow by erosion and corrosion processes. Some of the systems with operations involving this problem are: heat exchangers, steam and gas turbines, aircraft engine flow inlets and many others. Different coatings have been introduced recently to control the resulting metal wastage to tolerable levels. The objective of the reported research conducted in the last few years were to develop CVD erosion barriers for surface protection of metal and ceramic materials like: Ni-based superalloys, stainless steel, cemented tungsten carbide, and mullite at high temperatures, and to study the erosion behavior of the coatings. Thermal and micro-wave plasma CVD techniques were utilized to apply titanium carbide (TiC), titanium nitride (TiN), alumina (Al₂O₃), and polycrystalline diamond (PCD) on different substrates, frequently used for manufacturing of turbine and rocket components, cutting tools, and high-temperature parts. The erosion behavior of the coated specimens were investigated experimentally by exposing them to abrasive particle-laden flow in a high temperature wind tunnel. The eroded surfaces were then examined by scanning electron microscopy (SEM). The obtained results reveal the effects of velocity, temperature and impingement angle on the erosion rate. In addition, further data show the variation of the coating erosion rate with the quantity of the abrasive particles used. It was found that the CVD ceramic coatings protect better the base materials at elevated temperatures. The coated alloys reveal one order of magnitude less wear compared to some commercial non-CVD coating on the same substrates. The conducted study demonstrates that the tested CVD coating provide an excellent erosion resistance to MAR 234, Waspaloy, INCO 718, stainless steel 410, WC-Co, and mullite-based ceramic, when exposed to high temperature in particulate flow environment.

In this paper, special attention is given to CVD polycrystalline diamond coatings for wear protection. New experimental data at elevated temperatures are obtained and presented, which demonstrate that PCD is emerging as a promising erosion protective coating for high temperature applications.