Microstructure and High-temperature Tribological Properties of HVOF Sprayed CoCrWSi and Stellite-6 Coatings
To enhance the high-temperature wear resistance of F92 heat-resistant steel at 600 ℃ and 630 ℃,two kinds of CoCrWSi and Stellite-6 coatings were fabricated via high-velocity oxy-fuel (HVOF) spraying. The surface and cross-sectional characteristics,as well as the phase composition of the coatings,were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Micro-hardness measurements were conducted with a Microvickers hardness tester (HV-1000STA). The tribological properties and volumetric wear rates were evaluated with a high-temperature tribotester (UMT-TRIBOLAB) and a two-dimensional profilometer (TencorD-100),with wear morphology and phase analysis performed by SEM and XRD. The SEM revealed that both coatings were well-adhered to the substrate,with smooth surfaces,uniform internal structures,and no cracks,averaging a thickness of approximately 200 µm. XRD identified the main phases of the coatings as Co,Cr7C3,and CrSi2 at room temperature. The presence of Cr7C3 and CrSi2 phases in both coatings contributed to increasing hardness and wear resistance. The Co phase served as a lubricant,reducing the wear rate during sliding. Hardness and wear resistance tests indicated that the Vickers hardness of the CoCrWSi and Stellite-6 coatings were 3.12 and 2.68 times greater than that of the F92 substrate,respectively. The average friction coefficients for the F92 steel at 600 ℃ and 630 ℃ were 0.87 and 0.86,with corresponding volumetric wear rates of 0.49×10-4 mm3/(N·m) and 1.11×10-4 mm3/(N·m). The primary wear mechanisms for the F92 matrix were identified as fatigue,adhesive,and oxidation wear. Compared with the substrate,the CoCrWSi coating demonstrated a significant reduction in friction coefficients (68％ and 71％) at two temperatures,which were about 0.28 and 0.25,respectively. The volumetric wear rates were reduced by about 95％ and 97％,which were 0.20×10-5 mm3/(N·m) and 0.30×10-5 mm3/(N·m),at both temperatures,respectively. This was mainly attributed to the lubricating effects of internal Cr2O3,γ(Co),and Co3O4 phases. In contrast,the Stellite-6 coating exhibited a lesser improvement in wear resistance,with average friction coefficients of 0.85 and 0.71,and wear rates of 0.32×10-4 mm3/(N·m) and 0.57×10-4 mm3/(N·m). The Stellite-6 coating suffered from more severe wear,primarily adhesive wear,with substantial abrasive chip accumulation. The CoCrWSi coating showed minimal wear at 600 ℃ AND 630 ℃,with wear mechanisms dominated by abrasion and adhesion. The research findings indicate that HVOF-applied Stellite-6 and CoCrWSi coatings significantly improve the tribological properties of F92 steel at elevated temperatures,with CoCrWSi offering superior protective performance. This work employs high-velocity oxy-fuel spraying technology to deposit CoCrW coatings infused with a minor amount of Si onto the surface of F92 heat-resistant steel. It also conducts a comparative investigation into the tribological behavior of the F92 heat-resistant steel substrate,CoCrWSi,and Stellite-6 coatings under simulated actual working temperatures (600 ℃ and 630 ℃),analyzing the wear mechanisms involved. The objective of the findings is to supply substantiated data to enhance the knowledge base regarding the high-temperature durability of CoCrWSi coatings on F92 steel.
CoCrWSi coatinghigh-velocity oxy-fuel sprayinghigh temperature frictionStellite-6 coatingwear mechanismtribological properties
万方数据
维普
