Improvement Of Wire Flame Spray Equipment And Research On The Process Of Wire Flame Spraying Mo Coatings

Wire flame spray technology has been widely used due to its low cost and superior coating properties, which makes it play an important role in the remanufacturing process. With the resource and environment problems becoming increasingly prominent, near-zero emission, reducing negative effects on the environment, obtaining high performance thermal spray coatings with less energy and material should be the direction of long-term development for thermal spray industry, improving the level of automation and efficiency of wire flame spray equipments could be an effective way. Currently, domestic wire flame spray equipments are on the way out for they can’t meet the growing demands of environmental protection, productive efficiency and products’ qualit y in new period. Therefore, speeding up domestic wire flame spray equipments’ automation improvement, and making relative process research is very urgent. Supported by the National 863 Program “Environmental friendly surface treatment technology and equipment development”, this paper made automation improvements for grit-blasting equipment and wire flame spray equipment, then carried out research of grit-blasting and wire flame spraying Mo coatings process by the improved equipments, analyzing how the process parameters affect coatings’ performance. The main results and conclusions of this paper are as follows:(1) Automatic grit-blasting and wire flame spray equipments with closed loop turntable were developed. Moving speed of grit-blasting gun and wire flame spray gun, wire feeding speed, mass flow of oxygen and acetylene and some other parameters can be easily and accurately set through newly designed control system with human machine interface. Automatic ignition device has been designed for wire flame spray equipment, the equipment can operate automatically with the aid of flame and gas monitoring systems.(2) Process of grit-blasting pretreatment was studied. The result shows that, surface roughness parameters Ra, Rz increase with grit size’s increasing. Ra, Rz increase with gritblasting gun movement speed’s decreasing. On the whole, Ra, Rz increase with blasting pressure’s increasing, but it fluctuates on a small scale. The relationship between Ra, Rz and grit-blasting angle is not clear.(3) Process of Wire flame spraying Mo coatings were studied. When acetylene flow is sufficient, Mo coating’s adhesion strength and microhardness increase obviously wit h oxygen flow’s increasing. With acetylene flow’s increasing, Mo coating’s cohesio n strength increases slightly, while microhardness decreases. Spraying particles’ temperature and velocit y reach optimal combination with the spraying distance o f 90~110mm. The coating has a combination of high cohesion strength and microhardness when wire feeding speed is within 300~500mm/min,(4) The test result of Mo coatings’ adhesion or cohesion strength shows that, Mo coating and steel substrate have good adhesion strength, rupture is within the Mo coating, mostly locates in the first and second stack, while the coating’s thickness has poor influence on the cohesion strength.(5) Under dry condition, the result of ring-block wear test between Mo coatings and GCr15 counterpairs shows that, the wear mechanism of Mo coatings are mainly adhesive wear, accompanied with fatigue wear. Wear mechanism of GCr15 counterpairs is mainly adhesive wear when Mo coating’s microhardness is low, then turns into abrasive wear when the coating’s microhardness becomes greater. Friction coefficient is between 0.66~0.84 in steady wear period, and the friction coefficient becomes lower with the increase of coating’s hardness. Mo coating’s wear resistance is better with higher microhardness.