Evaluation of hillock-like deposition behaviour of HVOF thermal spray coatings using rotary shutter procedure

Abstract

Evaluation of hillock-like deposition behaviour of WC/Co coatings was performed using a rotary shutter procedure coupled with 100 passes of high velocity oxy fuel thermal spraying. During the spraying procedure, a DPV 2000 in situ diagnostic instrument was used to monitor the temperature and velocity of inflight particles. The microstructure of the coatings was analysed using an optical microscope to monitor the porosity and thickness distributions at various positions of the hillock-like coatings. A 7·1% porosity was observed at the centre of the hillock-like coatings, and a 10% porosity was observed at the edge, each at a spraying distance of 200 mm. The centre area of hillock-like coatings exhibited almost a 30% decrease in porosity compared to the edge area. The results indicate a higher quality structure at the centre area of the hillock-like coatings.