The Research For Process Of Preparing Micro-metallurgical Bonding Coating By Arc Spraying

The bonding form between thermal spraying coating and substrate is generallymechanical bonding, and the structure of the coating is typically lamellar which leadsto anisotropy of coatings’ properties. So interlayer failure and coating’s spalling fromsubstrate are common which restrict the application of thermal spraying technology.In order to increase the bond strength, we use spray welding and laser or plasmacladding to eliminate the porosity and the lamellar structure. Higher heat sourcemakes matrix surface melt and form metallurgical bonding. However, the temperatureof substrate is too high in these ways which affects the properties of substrate andsurface coating.The purpose of the reaserch is to make the surface of substrate melt to formmicro-metalurgical bonding between coatings and substrates, eliminate anisotropy ofproperties and increase the bonding strength of the coating. Of course, the temperatureof the substrate cann’t rise to a high value during the spraying prosess.We designed a new arc spraying system according the purpose of research. Thedesignation of the system includes choosing power source, designing wire feedingsystem and improving the structure of spraying gun. We choose NBC-500weldingpower source which has big output power, and design the wire feeding system whichcontains two wire feeders to feed two wires which connect two polars of power.During arc spraying process, we did process stability experiment to study theeffects of many factors on system stability. We obtained the following conclusion: onthe basis of the two wires’ centring, when the extension elongation of two wires is10-15mm, the wire which connects negative polar is controlled by constant wire-feedsystem, and its diameter is1.2mm, the wire which connects positive polar of powersource is controlled by independent wire feeder, and its diameter is1.6mm. Thesystem can work well with good stability. When we add pressure gas to the systemand the gas pressure is045MPa, the system can atomize the molten drop well and thesize of atomized particals is small and homogeneous.We sprayed the substrate by the arc spraying system to study the effectsof the processing parameters on metallurgical rate, porosity rate of coatings andthe temperature of substrate. We optimized the process and obtained the best:when the spraying distance is100mm, arc voltage is32.5V, spraying current is 231A, gas pressure is0.45MPa, preheating temperature is110℃, we can produce the coating with high metallurgical bonding rate.