Crack Formation And Control Of Laser Cladding Ni60/WC Coatings On 45 Steel

As an emerging surface modification technology,laser cladding technology has been applied in many engineering fields.However,the high-hardness coatings are prone to crack during laser cladding,which limits the application of this technology in the engineering field.Based on this,the research on the causes and control methods of cracks in high-hardness cladding coatings has great theoretical and practical significance.This paper takes the surface cracks of the cladding layer as the research object,summarizes the causes of the cracks and the influencing factors that cause the cracks,explores the influence of the coating composition and process parameters on the cracks,and studies the optimization of process parameters,preheating,and laser remelting.The effectiveness of methods such as modification with rare earth Ce O₂ on the crack control of the cladding coating,a series of crack-free Ni60/WC coatings were prepared,and the structure and performance of the series of coatings were characterized.Studies have shown that the main reason for the cracking of the cladding layer is that the residual stress of the cladding coating is greater than its yield strength.The main factors affecting the cracking of the cladding coating are the cladding material,the structure of the cladding layer,the size of the workpiece and the cladding process parameters With the increase of WC content,the crack rate on the surface of the cladding coating gradually increases;the main effect of each process parameter on the surface crack rate of the cladding coating is scanning speed>overlap rate>laser power>powder feeding rate.Methods such as optimization of process parameters,pre-heat treatment,laser remelting and rare earth Ce O₂modification can effectively reduce the surface crack rate of Ni60/WC cladding coatings.Among them,the optimization of process parameters can only control the cracks of Ni-based composite coatings with a WC content of less than 30%,while methods such as pre-heat treatment,laser remelting and rare earth Ce O₂ modification can treat Ni-based composites with a WC content of less than 50%.The cracks of the coating are controlled.The four methods of controlling cracks have important engineering application value,but they have their own advantages and disadvantages in terms of control effectiveness,process cycle,production cost,etc.,and they can be selected reasonably according to the actual situation.