Experimental Research On HVOF Tungsten Carbide Coating By Grinding

HVOF(high velocity oxyfuel spraying) WC-Co high hardness coating materialbrings great challenge to the processing technologies. The coating material achieved byHVOF have low porosity、high bond strength、high microhardness and high wearresistance. In recent years the HOVF method obtained the rapid development, also havemade great achievements. Excellent comprehensive performance makes its can only usediamond grinding wheel machining.There is only a little of research taked on thisdomain at home and abroad. In this paper, the experimental study on the grindingprocess of HVOF WC-10Co-4Cr coating with45#steel substrate is conducted. The mainresearch content was as follows:1. The grinding force of the HOVF WC coating with different grinding parametersare measured by using a piezoelectric crystal dynamometer.2. Optimize the method of temperature measurement using thermocouple. Basedon the grinding temperature measured during grinding, the average temperature of thegrinding zone and the coating-substrate faying face were calculated by the ANSYS3. Analyze the effect of the different grinding parameters to the grinding quality bymeasure the surface roughness、surface microstructure and the subsurface damage.Research the removal mechanism of HOVF tungsten carbide coating.The results show that: the grinding force decreases with the increase of wheel speedwhile increases with the increases of table speed and grinding depth. The ground surfaceroughness improves with the increase of the wheel speed and worsen with the increasesof table speed and grinding depth. Besides there is relationship between the surfaceroughness and the structure of the coating itself. With the help of finite elementsimulation, the temperature of the coating surface and coating-substrate faying face canbe deduced. The temperature of the coating surface and coating-substrate faying faceincreases with the increase of grinding depth,first increases and then decreases with theincrease of table speed.The morphology of surface and sub-surface of the HOVF WCcoating with different grinding parameters were investigated by using scanning electronmicroscope and VHX-1000three-dimensional microscope.It is found that the grindingsurface is composed of trench marks formed by abrasives scratch and pits formed bybrittle fracture. The damages of the subsurface include: cracks、micro broken、materialpulverization and stomatal collapse. Through a large number of experiments analyzed the impact of various processingparameters on the processing quality evaluation factors such as grinding force、surfaceroughness、grinding temperature、surface damage and subsurface damage，the test resultshave a certain significance.