Microstructure and tribological properties of supersonic plasma sprayed Ni-based high entropy alloy coatings optimized by response surface method

FeCoNiCrAl high entropy alloy (HEA) coatings were prepared through the employment of the plasma spraying technique. The plasma spraying process parameters were optimized by means of the response surface methodology (RSM). A Box Behnken Design (BBD) was adopted to evaluate the effects of spraying power, spraying distance, and main gas flow rate on the porosity and microhardness of the coatings. Microscopic analysis and mechanical performance testing were conducted on the coating. Research showed that FeCoNiCrAl high entropy alloy coatings with different powers all consisted of body-centered cubic (BCC). The results revealed that the spraying power was the key factor affecting the porosity and microhardness of the coatings. With the change of spraying power, the melting degree of FeCoNiCrAl powder differed, and various spreading droplets appeared on the coating surface. The porosity and microhardness of the optimized FeCoNiCrAl coating were 0.45 % and 476.98 HV_0.1, respectively, which were in close agreement with the model predictions. The results obtained from TEM indicated that the grains of the coating were highly crystallized and dislocations were existent within them. The optimized coating manifested a notable augmentation in wear resistance. Fatigue wear and abrasive wear were determined to be the predominant wear mechanisms discerned in the coating. Through the optimization of spraying parameters, the FeCoNiCrAl coating had been refined, thereby having furnished a reference for future investigations into plasma - sprayed FeCoNiCrAl high entropy alloy coatings.