Study On The Generating Mechanism And Control Methods Of High Hardness Laser Cladding Coating Cracks

In this paper, CO2laser is adopted with the Feeding method of synchronization together to prepare the high hardness of laser cladding coating. It makes a research on the influence on cracks of laser cladding coating with preheating temperature, mass fraction of laser scanning technology, rare earth elements, Ni/WC and gradient method of laser cladding. With the aid of modern testing equipment, laser cladding coating tissue morphology, microhardness and wear resistance are tested and analyzed.The analyzing results demonstrate that:Increasing the preheating temperature can suppress cracks of the laser cladding coating, adding rare earth elements can remove cracks in the laser cladding coating, adding the right amount of Ni/WC can improve the wear resistance of the laser cladding coating but to much Ni/WC can easily cause cracks. The fundamental cause of cracks in the laser cladding coating is the excessive difference in thermal expansion coefficient between the lasers cladding coating. The residual stress produced during solidification processes has effect on the grain boundary, which makes the grain boundary hold a cracking tendency, and generates cracks when the residual stress exceeds the yield limit of the material.By means of gradient laser cladding controlling method, using Co47-49-1alloy powder including5%Ni/WC, making use of the method that preheating the base to500℃and slow cooling after cladding; it can get high hardness gradient laser cladding coating without cracks on the surface, using1500W process parameters of laser power,+50mm defocusing distance,300mm/min scanning speed,12V powder feeding voltage,300L/h powder feed gas flow. Hardness test shows that the hardness of high hardness gradient coating can get734HV0.1and the wear resistance is increased by about5.68times.