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This paper aims to experimentally investigate the effect of graphene nanoplatelets (GNPs) doped Al2O3 coating deposited on the surface of cemented carbide substrate using suspension high velocity oxy fuel (SHVOF) thermal spraying technique. Scanning electron microscopy was applied to characterize GNPs doped Al2O3 feedstock, the surface morphologies of cemented carbide before and after spraying, and the wear track morphology of cemented carbide after wear tests. The phases of GNPs doped Al2O3 feedstock, uncoated and coated cemented carbide were analyzed by X‐ray diffraction. The existence of GNPs was analyzed by Raman spectroscopy. A mixture of un‐molten and molten splats formed on the surface of cemented carbide substrate after SHVOF thermal spray. The average coefficient of friction (CoF) of coated samples was slightly lower than that of uncoated samples, which might be due to the friction‐reduction effect of GNPs. The wear rate of the samples was one order of magnitude higher than that of the alumina ball, showing that the wear of samples was the main wear between the friction couples. The wear mechanism of uncoated sample was mainly fatigue spalling, and that of cemented carbide substrate coated with GNPs doped Al2O3 coating was mainly plowing and abrasive wear. [ABSTRACT FROM AUTHOR]

In our present work, alumina/BNNTs and alumina/MoS 2 coatings were deposited onto stainless steel substrates by solution precursor high velocity oxy-fuel thermal spraying. The phase evolution, microstructure and tribological properties of the two kinds of coatings were studied. Investigation of the phased content showed that Al 2 O 3 , BN and MoS 2 survived in the coatings after being sprayed with SHVOF technology. Cross-section images of the coatings showed that the interface between the coating and the substrate was well bonded, and there were no obvious particle inclusions and defects at the interface. The top morphology of the coatings exhibited certain degree of particle deformation, which was conducive to the formation of a more compact coating with less porous and better bonding strength with the substrate. Dry sliding tests showed that alumina/BNNTs and alumina/MoS 2 coating improved the tribological properties of the samples and they were suitable for low load friction conditions (5 and 10 N). A crack evolution model was proposed to analyze the failure of coatings. This work could provide a reference for the application of the two coatings in the field of friction and wear. • Alumina/BNNTs and alumina/MoS 2 were deposited onto a stainless steel substrate using SHVOF thermal spraying. • The top morphology of the coatings exhibited a certain degree deformation of the particles. • The wear mechanisms of the coatings were dominated by coating peeling off, adhesion and abrasive wear. • A crack evolution model was proposed to analyze the failure of coatings. [ABSTRACT FROM AUTHOR]

The incorporation of graphene-based nanodispersoids in ceramic coatings is known to enhance the wear behavior of these materials. In this study, for the first time, alumina/graphene nanoplatelets (GNPs) coatings were deposited through Suspension High Velocity Oxy-Fuel (SHVOF) thermal spray on Al 2 O 3 /TiC substrate composites, which were laser microtextured with grid and line surface patterns. Dense coatings with around 8−10 μm thickness were obtained by spraying alumina suspension containing 1 wt. % GNPs. The tribological performance of the alumina/GNPs coatings on the Al 2 O 3 /TiC substrate composites was evaluated using ball-on-disc sliding wear tests. The alumina/GNPs coated Al 2 O 3 /TiC substrate composites textured with grid pattern showed the best tribological performance reaching a steady coefficient of friction (CoF) at lower sliding distances and presenting the lowest wear rate of the Al 2 O 3 /TiC substrate composites and the counterbody. [ABSTRACT FROM AUTHOR]

Grid and line textures were made on the top surfaces of WC-TiC-Co cemented carbide substrates. Suspension High Velocity Oxy-Fuel (SHVOF) was utilized to deposit alumina and graphene nanoplatelets (GNPs) coating on the textured surfaces. The friction and wear behaviors of the Alumina/GNPs coating were evaluated using dry sliding wear tests against alumina balls. The friction reduction mechanism of alumina/GNPs coating was presented. GNPs in the alumina coatings played a significant role in reducing the coefficient of friction (CoF) up to 40 % and improving the wear resistance properties of the coating. A stress distribution model of the friction contact zone was provided to analyze the tribological performance of the textured sample. The friction reduction mechanism for alumina/GNPs coating was discussed. These results offer a benchmark for further studies combining microtextured surfaces and SHVOF thermal sprayed coatings as promising candidates for high wear resistant applications. • The stress distribution model of the friction contact zone was provided. • A wear mechanism for GNPs doped Al 2 O 3 coatings was proposed. • A thin, controlled layer which preserved the texture surface morphology was formed. [ABSTRACT FROM AUTHOR]