Study On Microstructure And Abrasive Wear Of WC/Co Coating Deposited By Denotation Spraying

Thermally sprayed tungsten carbide-based coatings are being widely used for a variety of wear resistance applications.These coatings deposited by detonation gun spray(DS)techniques are known to provide improved wear performance.Due to higher costs and lower productivity, DS is generally applied in the military and aerospace fields;recently it is gradually extended to the civilian direction, and has achieved good economic efficiency.In order to increase the abrasive wear resistance of 316L stainless steel,16 coatings were deposited on 316L stainless steel with various sizes of WC grain and cobalt percent WC/Co powder and various spraying permanents by using denotation gun spraying.The structure of the feedstock powders and the coatings were analyzed by XRD.The characterizations of spraying feedstock powders,microstructure and wear surface micrographs of these coatings were analyzed by SEM.Porosity measurements were performed on the sectioned and polished surface of the coating using a Zeiss Axiovert 40 MAT microscope fitted with a MIAPS image analyzer, bond strength of coatings were tested by the electronic tensile machine,The fracture toughness of all coatings was evaluated using a Vickers indenter. The abrasive wear resistances of all the three coatings have been studied by wet sand rubber wheel abrasion tester. The influence of the WC grain size, cobalt content in the WC/Co powder and D-gun spray permanents on the coating performance had been explored.The main conclusions are as follow:1.The ratio of oxygen and fuel has significant influence on the quality of coating,the hardness of coating increased with the amount of the decomposed W2C or W phase.The abrasive wear resistance of WC/Co increased with the increasing of amount of the decomposed W2C until the metal W appeared because of high brittleness of coating.2.The porosity and fracture toughness of the coating decreased with the increasing of coating hardness.3.The abrasive wear resistance of WC/Co coating increased with the decreasing of WC grain size.4.The abrasive wear loss increased with the increasing of abrasive particle size and cobalt.5. The mechanisms of wear can be deduced as that:firstly, it was by selective removal of the binder and WC carbides particles were attritive worn by abrasive particles,and then plastic deformation and fatigue due to the repeated action of the carbide particles resulting in their fracture,crashing and eventual pull out.