The erosion of a Super D-Gun*, a D-Gun*, and a plasma chromium carbide coating of interest to the power generation industry was compared with that of 400-series stainless steels in tests with chromite erodents of differing particle size, and with alumina erodent. Some tests were conducted at 550-degrees-C with particle velocities of 305 m s-1 and some at room temperature with particle velocities near 49 m s-1. The 400-series stainless steels were found to exhibit maximum erosion rates at impingement angles close to 30-degrees when attacked by chromite fractions with particles no larger than 120 microns, but not when attacked by larger chromite particles or by alumina. The ratios of the erosion rates of the coatings to those of the steel at low angles were also low when the larger chromite or the alumina were used, but attained values of 9:1 or greater with the smaller chromite; the highest ratios were obtained at room temperature, with the smallest chromite. For all conditions, the Super D-Gun coating eroded more slowly than the D-Gun coating, which eroded more slowly than the plasma coating. The erosion resistance of all the coatings was enhanced by pre-oxidation.
