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Owing to their high hardness, fracture toughness and oxidation resistance, tungsten carbide (WC) coatings are extensively deposited on parts that operate in demanding applications, necessitating wear, erosion, and corrosion resistance. The application of thick and hard WC coatings has an inevitable effect on the original dimensions of the parts, affecting the geometrical tolerances and surface roughness. The capability of achieving a sub-micron surface finish and adhere to tight geometrical tolerances accurately and repeatably is an important requirement, particularly with components that operate in high-precision sliding motion. Meeting such requirements through conventional surface finishing methods, however, can be challenging due to the superior mechanical and tribological properties of WC coatings. A brief review into the synthesis techniques of cemented and binderless WC coatings is presented together with a comprehensive review into the available techniques which are used to surface finish WC-based coatings with reference to their fundamental mechanisms and capabilities to process parts with intricate and internal features. The binderless WC/W coating considered in this work is deposited through chemical vapour deposition (CVD) and unlike traditional cemented carbide coatings, it has a homogenous coating structure. This distinctive characteristic has the potential of eliminating key issues commonly encountered with machining and finishing of WC-based coatings. Here, six contact and non-contact surface finishing techniques, include diamond turning, precision grinding, superfinishing, vibratory polishing, electrical discharge machining, and electropolishing are discussed along with their current use in industry and limitations. Key challenges in the field are highlighted and potential directions for future investigation, particularly on binderless WC coatings, are proposed herein.

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Nanostructured tungsten/tungsten carbide (W/WC) coatings produced by chemical vapour deposition are promising WC based coatings for applications where galling wear is prevalent due to the high hardness, toughness and stacking fault energy which the coatings possess despite low hardness to elastic modulus ratio (H/E). In this work the galling resistance of W/WC coatings has been studied through tibometer tests using sliding speeds of 0.014 m s −1 and contact pressures of up to 810 MPa. The study investigates the effects of surface finish and the use of similar and dissimilar material combinations on galling wear. Results show that self-mated stainless steel AISI 316 behave poorly under dry sliding wear conditions whilst uncoated stainless steel tested versus W/WC coating combinations are affected by galling due to material transfer forming a stainless steel on stainless steel tribosystem. The best performance was recorded for self-mated W/WC which did not develop any signs of galling even at the highest contact pressures (810 MPa) contradicting the common practice that the use of dissimilar materials can help prevent galling.