Structure Property Relationship of Suspension Thermally Sprayed WC-Co Nanocomposite Coatings
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Tribomechanical properties of nanostructured coatings deposited by suspension high velocity oxy-fuel (S-HVOF) and conventional HVOF (Jet Kote) spraying were evaluated. Nanostructured S-HVOF coatings were obtained via ball milling of the agglomerated and sintered WC-12Co feedstock powder, which were deposited via an aqueous-based suspension using modified HVOF (TopGun) process. Microstructural evaluations of these hardmetal coatings included transmission electron microscopy, x-ray diffraction, and scanning electron microscopy equipped with energy dispersive x-ray spectroscopy. The nanohardness and modulus of the coated specimens were investigated using a diamond Berkovich nanoindenter. Sliding wear tests were conducted using a ball-on-flat test rig. Results indicated that low porosity coatings with nanostructured features were obtained. High carbon loss was observed, but coatings showed a high hardness up to 1000 HV2.9N. S-HVOF coatings also showed improved sliding wear and friction behavior, which were attributed to nanosized particles reducing ball wear in three-body abrasion and support of metal matrix due to uniform distribution of nanoparticles in the coating microstructure.
Keywordsnanoindentation nanostructured coating suspension spraying tribology WC-Co coating wear
Authors acknowledge the support of Youssef Elakwah at Alfaisal University KSA in conducting the nanoindentation experiments. Irina Shakhverdova (Fraunhofer IWS) is thanked for support in evaluation of XRD pattern. Financial support of Saudi Aramco for the research project is also gratefully acknowledged.
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