Experimental study on water droplet erosion resistance of coatings (Ni60 and WC-17Co) sprayed by APS and HVOF

In order to simulate the actual operating environment of the last stage blades of steam turbines, especially under the condition of high-speed liquid-solid impact (over 600 m/s), a new experimental rig for testing the water droplet erosion (WDE) characteristics is built, and three kinds of specimen structure adapted to different impact angles are designed. The WDE resistance of the four kinds of thermal spraying coating, which are prepared using atmospheric plasma spraying (APS) and high velocity oxygen fuel spraying (HVOF) with two kinds of alloy powder (Ni60 and WC-17Co) on the substrate material (17-4PH stainless steel), are tested using the experimental rig. In this paper, three-dimensional optical microscopy is used to obtain the morphology of WDE grooves on the target surface of different coating specimens. During the measurement process, three characteristic sections are selected, and the average profile of erosion grooves at different times are given respectively. The average area loss of the erosion section is obtained with integrating method. The cumulative loss curves are analyzed and the WDE resistance of the present coatings are compared. It is found that the HVOF-WC17Co coating is of the best WDE resistance.