Study of High-Temperature Sliding Friction Properties of Protective Coatings for Steam Turbine Valve Components

Abstract

In order to address the problem of high-temperature reciprocating friction and wear of protective coatings for steam turbine valve components, NiCr/Cr3C2-NiCr metal-ceramic composite coatings were prepared on the surface of martensitic heat-resistant steel substrate by high-velocity oxygen-fuel spraying process (HVOF).The high-temperature sliding wear characteristics of the coatings were tested, and the high-temperature wear behavior of the coatings at 630 ℃was studied at different frequencies, so as to analyze the high-temperature sliding wear performance of protective coatings for valve parts.Results showed that the NiCr adhesive coatings improved the bonding strength and thermal stability of the coating to a certain extent,and the tribological properties of coatings were affected by the friction products.Additionally,the wear surface of the coating mainly manifested as adhesive wear and oxidation wear.The reciprocating frequency affected the high-temperature wear resistance of the coating through the intensity of oxidative wear, and the increase in the frequency accelerated the process from formation to rupture of the oxide film.Besides, under the condition of discontinuous wear, the wear rate of the coating decreased by 35.6%compared to that of continuous wear mode.

Keywords

• hvof； nicr/cr₃c₂-nicr coatings； high temperature frictional wear