Erosion resistance of coatings for metal protection at elevated temperatures

As experimental study was conducted to investigate the behavior of coated metal substrates exposed to erosion by chromite particles. Chemical vapor deposition technique (CVD) was used to apply titanium carbide (TiC) on nickel based alloy INCO 718 and on AISI 410 (stainless steel 410). Another group of specimens made of the same substrate materials was subjected to surface treatment by nitriding in glow discharge plasma (ion nitriding). The erosive wear of the samples was investigated experimentally by exposing them to particle laden flow at velocities from 180 to 305 m s(-1). temperatures from ambient to 538 degrees C and impingement angles from 20 to 90 degrees in a specially designed erosion wind tunnel. The erosion results show the effect of the velocity, temperature, and the impingement angle on the erosion rate. The cumulative effects of the impacting particles mass on the weight loss and on the erosion rate of the protective coatings were also investigated. The coating erosion rate variation with the impingement angle shows brittle erosion patterns for the TiC coating and ductile patterns for the ion nitrided substrates. The CVD coated INCO 718 nitrided substrates. The CVD coated INCO 718 revealed longer lifetime than that of coated stainless steel 410 in sequential tests. Both substrate materials coated with TiC showed one order of magnitude less erosion rates compared to some commercial coatings on INCO 718. The ion nitrided samples did not reveal any improved erosion resistance compared to the uncoated metal substrates. In addition, the eroded surfaces were examined by scanning electron microscopy (SEM). This study indicates that the rested CVD ceramic coating provides very good erosion resistance for stainless steel 410 and INCO 718 when exposed to elevated temperatures.