Influence Of Process Parameters And Substrate Temperature On The Micro-structure And Property Of Detonation Sprayed WC Coatings

Detonation spray as a means of preparing high quality coatings, has been widely used in military fields such as aerospace and nuclear industry. With the development of civilian industry and the popularization of equipment, D-gun has increasingly applied in the civilian industry. In the process of detonation sprayed tungsten carbide coating, the selection of technological parameter(such as spraying distance, the gas flow rate, substrate temperature, etc.) is very important for the structure and related physical or mechanical properties of the coatings.WC coatings were prepared by DNB-3 detonation system using WC10Co4Cr powder which made by sintering and broken. Prepare the WC coating under different spraying distance and oxygen fuel ratio. Organization, hardness, phase structure and fracture toughness were analyzed, thus optimizing the spraying parameters. Then preparing another WC coating by using optimized parameter under the condition of different substrate temperature. Explore the particle flattening, the hardness, the grain size and related properties of the coatings. This played an important role for preparing high quality WC coatings from the angle of the substrate.The main conclusions are as follows:(1) The increase of spraying distance will make the particle stay a long time in the high temperature flame, the resistance of air will be larger, its speed has reduced. The porosity of the coating will be increased. At the same time, a part of WC is decarburizing and become W2C, which has a higher hardness. the fracture toughness of the coating has decreased.(2) After reducing the oxygen fuel ratio appropriately, the combustible mixture gas can fully burned, the explosion energy is enough to melt all binding phase, and bump on the surface of the substrate at a higher speed. At this time, the porosity of the coating is low and the decarburization degree of WC has reduced, the fracture toughness is increasing.(3) Substrate at room temperature, the highest hardness is in the central near the surface of the coating, While the substrate preheat to 300℃, the highest hardness located near the base. With the increase of substrate’s temperature, the average grain size of WC10Co4Cr coatings is decreasing.(4) substrate under the condition of no-preheating, a single WC particles is "petals" shape, Degree of melt is bad and the pore number is lot. Substrate after 300℃ preheat, the particle become "pancake" shape,Co phase infiltrate well between WC particles. The pore number is obviously low. The tensile test result shows that the bonding strength under the condition of preheating is higher than the one which is sprayed at room temperature.