Multi-Angle Laser Cladding Process Optimization And Morphology Study

The traditional laser cladding technology is mainly based on the vertical downward operation of the cladding nozzle.In practical engineering applications,there are many parts that are large in volume and difficult to move or have complex surface shapes.When repairing them,the cladding nozzle needs to be deflected at a large Angle,which leads to changes in the stress state of powder and molten pool.Therefore,the study of the influence of process parameters on the morphology and mechanical properties of laser cladding under different angles of laser cladding nozzle deflection can provide theoretical and practical basis for multi-angle laser cladding repair.Firstly,the powder feeding method was optimized and the fixture was designed.The converging focus of the powder beam with the deflection of 45°,90° and 135° was measured.When the carrier gas flow rate was 15 L/min,the adverse effects caused by the deflection Angle and gravity of the powder could be overcome.Experiments of laser cladding of 316 L stainless steel powder with deflection 0°,45°,90° and 135° were carried out,and relatively regular cladding layers were obtained.The effects of process parameters and deflection Angle on the morphology of cladding layer(section size,top offset,etc.)are studied.The results show that increasing the scanning speed(≥6 mm/s),reducing the powder feeding amount(≤18 r/min)and selecting the appropriate laser power(1100 W-1300 W)can ensure the morphology quality of the cladding layer and reduce the top offset.Then,the effects of lap rate,process parameters,scanning direction and lap mode on the morphology and characteristic parameters(penetration height,penetration depth,surface smoothness)of 316 L stainless steel powder with deflection 90° were studied.The results show that the surface smoothness of multi-channel laser cladding can be improved by changing single parameters(such as increasing laser power,increasing scanning speed,reducing powder delivery),vertical scanning,and staggered lap cladding without changing other parameters.At the same time,defects in the cladding layer can be avoided.Finally,the microstructure and hardness of the multi-angle laser cladding layer are analyzed.The hardness of the cladding layer(184.2-191.2 HV)is higher than that of the substrate(168.5 HV).The tensile mechanical properties of the substrate and the 0°and 90° cladding layer were tested,and the fracture mechanism and fracture morphology were analyzed.The results show that the fracture surface of the substrate has more dimples and deeper dimples,and its plasticity is better than that of the cladding layer.The yield strength of the cladding layer(361.04-390.83 MPa)is higher than that of the cladding layer(337.61-354.67 MPa),and the bending strength ratio of the substrate(0.44-0.5)is lower than that of the cladding layer(0.68-0.75).The surface of 20# seamless steel pipe was repaired by a 90° deflection multi-channel laser cladding process.The overall surface of the cladding layer has a high flatness,and the deflection Angle laser cladding can meet the practical repair application.