Influence of high hydrostatic pressure on tribocorrosion behavior of HVOF WC-10Co-4Cr coating coupled with Si3N4 in artificial seawater

Abstract

The ambient pressure is increasing with depth of ocean, however there are few studies about the effect of the pressure on the tribocorrosion behavior. Thus, the influence of hydrostatic pressure on the tribocorrosion behavior of the HVOF WC-10Co-4Cr coating sliding against Si3N4 was studied. Hydrostatic pressures were 0, 20, 40, 60, and 80 MPa, respectively. Experimental results indicate that the hydrostatic pressure has insignificant effect on the friction coefficient of the tribo-pair. At 1500 rpm, the friction coefficient increases from 0.0215 to 0.0282 when the pressure rises from 0 to 40 MPa, and the difference between the maximum and the minimum wear rate is only 0.6 × 10−8 mm3/Nm, implying that the tribo-pair has good adaptability to different hydrostatic pressures. The results of potentiodynamic scanning show that the hydrostatic pressure has a slight promoting effect on the corrosion rate of WC-10Co-4Cr.Under corrosion-only condition, the corrosion rate increases from 0.006 mm/a to 0.0143 mm/a when the pressure ranges from 0 to 80 MPa. Friction promotes the corrosion behavior of WC-10Co-4Cr coating. Under tribocorrosion condition, depassivation of Cr and Co elements in WC-10Co-4Cr coating accelerates the dissolution of the worn zone and crevice corrosion, leading to the corrosion rate increases from 0.0112 mm/a to 0.0296 mm/a with the rising pressure. The wear mechanism of WC-10Co-4Cr is that the corrosion of the CoCr binder phase leads to the shedding of WC particles and part of the abrasive wear.