Study On Laser Cladding Technology Of WC Reinforced Ni-based Alloy On 42CrMo Steel Surface

The pick is an important part of the coal mining machine when it is working,and it often encounters problems such as wear and failure during the coal mining process.The use of surface technology to strengthen the pick body can greatly increase the utilization rate of the pick and reduce the cost.Compared with other traditional surface strengthening technologies,laser cladding technology can increase the surface hardness and wear resistance of the pick body effectively and form a high-quality cladding layer.First,single-track and multi-track multi-layer process experiments of Ni(Nickel)-based laser cladding coating with 0%,20%,and 40% Ni-clad WC(Nickel-clad tungsten carbide)were carried out on the 42 CrMo steel.The optimal process parameters were determined as follows: laser power 900 W,scanning speed 4 mm/s,powder feeding volume 10.16 g/min,shielding gas volume 15 L/min,and carrier gas volume 12 L/min.Microstructure observation showed that the structure of the Ni-based cladding layer with 0% Ni-clad WC was mainly fine dendrites and cellular crystals.The structure of the Ni-based cladding layer with 20% and 40% Ni-clad WC was more dense,the cladding layer had a good bond with the substrate.XRD phase analysis showed that the main phases of Ni-based cladding laser with 0% Ni-clad WC were Ni3 Fe,?-Ni,M23C6.The main phases of Ni-based cladding lasers with 20% and40% Ni-clad WC were Ni3 Fe,?-Ni,W2 C,WC,Ni2W4 C,and M23C6.The microhardness of the cladding layer increased because of the increase of WC content.When the content of Ni-clad WC was 40%,the average microhardness of the cladding layer reached 679.94 HV.Then,the temperature field and stress field of Ni-based cladding lasers with different Ni-clad WC content and gradient cladding laser(the content of Ni package WC changes in a gradient of 0%,20%,and 40%)were simulated.Adding Ni-clad WC caused different physical parameters in the cladding layer and between the cladding layer and the substrate.The peak temperature of the 40% Ni-clad WC reinforced Ni-based alloy coating was the highest,and the residual stress was the largest;Compared with the 40% Ni-clad WC reinforced Ni-based cladding laser,the stress of the gradient cladding laser along the laser scanning direction,perpendicular to the scanning direction and along the thickness direction were all reduced by about100 MPa.Finally,the preparation of the gradient cladding laser was carried out,and defects such as cracks were reduced.The microhardness increased from the bottom of the coating to the top,and the highest hardness was 669.5 HV.The average friction coefficients of matrix,Ni-based cladding lasers with 0%,20%,40% WC and gradient cladding lasers were 0.515,0.410,0.347,0.319,0.342.The Ni-based cladding laser with 40% Ni-clad WC had the highest wear resistance,followed by the gradient cladding laser.The wear form of the cladding laser without Ni-clad WC hard phase was adhesive wear.The cladding laser with WC hard phase had both abrasive wear and adhesive wear form.