Functionally Graded HVOF Sprayed NiCr-Al₂O₃ Coatings for Demanding Applications

Functionally graded (FG) coatings were manufactured by High Velocity Oxy-Fuel (HVOF) thermal spraying and tested aiming for the high temperature applications. Single layers were manufactured and their elastic modulus measured by using Impulse Excitation Technique (IET). Obtained data was used for modeling of optimal gradient structure. Dual feeding hose for HVOF gun was developed. Calibration procedure for the concurrent use of two powder feeders was performed. NiCr-Al₂O₃ coatings with coating thickness of 600 µm and 1000 µm were manufactured and tested. Promising results were obtained from high temperature corrosion tests.