Optimization of HVOF thermal spraying parameters to improve the oxidation resistance of MCrAlY coating using Response

In this research, effects of different coating process parameters on the final properties of thermal spray coatings obtained from HVOF method are investigated. For this aim, five different levels are considered for four effective parameters (Fuel injection rate, oxygen injection rate, powder injection rate and spray distance) on HVOF process by response surface method (RSM) and minimum porosity and minimum oxidation layer thickness are considered as the responses. To investigate the microstructure of coatings, Thermal Grown Oxide (TGO) thickness and porosity, a Scanning Electron Microscopy (SEM) and image analysis method are applied. Oxidation test has done at1100ºC for 50 hours on coated samples. Results show that (oxygen injection rate and powder injection rate), (fuel injection rate and powder injection rate), (powder injection rate and spray distance) have a reaction on each other in the TGO thickness value. Also, (oxygen injection rate and powderinjectionrate), (fuel injection rate and powder injection rate) have a little reaction on the porosity against the other parameters which haven’t any effect on it. Investigation of the coated sample with optimized parameters reveals that porosity of the coating is about 0.5% and TGO thickness is about 5.3 micrometer.