Microstructure and Properties of HVOF-Sprayed NiCrAlY Coatings Modified by Rare Earth

Rare earth (RE)-modified NiCrAlY powders were prepared by ultrasonic gas atomization and deposited on stainless steel substrate by high-velocity oxygen fuel spraying. The effects of the RE on the microstructure, properties, and thermal shock resistance of the NiCrAlY coatings were investigated. The results showed that the NiCrAlY powders were refined and distributed uniformly after adding RE, while the number of unmelted particles in the coatings was reduced. Moreover, the RE-modified coatings showed improved microhardness and distribution uniformity. The microhardness of the coating reached a maximum after adding 0.9 wt.% RE, being 34.4 % higher than that of coatings without RE. The adhesive strength increased and reached a maximum after adding 0.6 wt.% RE, being 18.8 % higher than that of coatings without RE. Excessive RE decreased the adhesive strength. The thermal cycle life of NiCrAlY coatings increased drastically with RE addition. The coating with 0.9 wt.% RE showed optimum thermal shock resistance, being 21.2 % higher than that of coatings without RE.