Abstract
To reduce the deformation and improve the quality of thin-walled parts repaired by laser cladding, a three-factor, three-level orthogonal experimental scheme was employed to clad Ni60 powder on thin-walled parts with a thickness of 3.5 mm. To measure the deformation of the thin-walled parts, a method of combining the meshing of the backs of the thin-walled parts and fixing one end of the parts during cladding was used. The effects of the powder feed rate, laser power, and scanning speed on the deformation of the thin-walled parts were studied via visual analysis and analysis of variance, and the process parameters that resulted in the minimum deformation were determined. The deformation process of the thin-walled parts and the causes of cladding stress were also studied, and the microstructure of the cladding layer with the minimum deformation was analyzed via scanning electron microscopy (SEM). The results reveal that the deformation of the thin-walled parts increased with the increase of laser power. The increases of the scanning speed and powder feed rate were found to reduce the deformation of thin-walled parts; the laser power was found to have a significant effect, and the powder feed rate was found to have no significant effect, on the deformation of thin-walled parts. The order of the influence of factors on the deformation of thin-walled parts from greatest to least was determined to be as follows: laser power > scanning speed > powder feed rate. The optimal parameters to obtain the minimum deformation and good metallurgical bonding of thin-walled parts were found to be a powder feed rate of 1.4 r/min, a laser power of 1100 W, and a scanning speed of 8 mm/s. From the bottom to the top, the crystal structure of the coating with the minimum deformation was found to be coarse dendrite, dendritic crystal, and equiaxed crystal.
Highlights
As an environmentally friendly remanufacturing technology, laser cladding technology has the advantages of resulting in a dense coating structure, a small heat-affected area, and environmental protection [1,2]
Laser cladding technology is widely used in automotive, steel, aerospace, mining machinery, petrochemical, and other fields due to its unique advantages when used in parts repair [3,4], and thin-walled parts are commonly used in the fields of aviation, aerospace, national defense advanced technology, and ships [5]
When repairing thin-walled parts, a large temperature gradient occurs between the cladding layer and the substrate, and there is a difference between the coefficients of thermal expansion of the substrate and the alloy powder; this leads to differences in the thermal expansion and cooling shrinkage of each local area, and cladding stress will occur in the cladding layer [13]
Summary
As an environmentally friendly remanufacturing technology, laser cladding technology has the advantages of resulting in a dense coating structure, a small heat-affected area, and environmental protection [1,2]. Laser cladding technology is widely used in automotive, steel, aerospace, mining machinery, petrochemical, and other fields due to its unique advantages when used in parts repair [3,4], and thin-walled parts are commonly used in the fields of aviation, aerospace, national defense advanced technology, and ships [5] It presents outstanding advantages, there remain many problems when repairing thin-walled parts via laser cladding, as it is difficult to control the process parameters [6,7,8]. Yan et al [26] carried out the on-site monitoring of the temperature under different process parameters via infrared cameras and thermocouples, and studied the effect of temperature on laser cladding deformation These studies have not fundamentally solved the problem of deformation that arises when laser cladding is used to repair thin-walled parts. This work presents a method for the process optimization of the laser repair of thin-walled parts in the fields of aerospace and national defense, as well as other cutting-edge technologies
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