Basic Research On Laser Cladding Forming Of Inclined Thin-walled Parts

Many parts not only have thin-walled structures but also with the characteristic of inclination. Typically, the shell of combustion chamber is one of those parts. The combustion chamber shell which manufactured with traditional methods is time-consuming, material-wasting and easily deformed. Technology of Laser cladding forming (LCF), which shows unique advantages in the fabrication of thin-walled parts, can directly forming metallic components meet the performance requirements. However, under three-axis and open-loop control, LCF of inclined parts has been a difficult problem to be solved. Currently, most of the references studied on the parts with single inclined angle, but there is no references about the method to clad arc-section inclined thin-walled parts the shell of combustion chamber has the same structure. For the characteristic of the inclined thin-wall parts, the methods of varying z-increments and laser input energy are adopted to deposit the arc-section inclined thin-walled parts with high geometrical precision and clad quality successfully. The main work done and results obtained are as follows:(1) The technology difficulties of LCF of arc-section inclined thin-walled parts are analyzed. The theoretical analysis on LCF of arc-section inclined thin-walled parts with variable z-increments, and on the process of varying laser input energy to reduce the effects of thermal accumulation and inclination angle changing is done in detail. Therefore, the clad quality of arc-section inclined thin-walled parts is improved. All of above provide theoretical basis for the following experiments of cladding thin-walled parts.(2) Considering the effects of single-layer offset on the cladding height, the corresponding relationship between offset and z-increment is investigated. A mathematical model of single-layer cladding height of uniform cross-section vertical thin-walled parts is built, and obtains the optimized theoretical z-increment0.139mm for vertical thin-walled parts. The model is verified by experiments. The relationship curve between offset and z-increment is obtained by laser cladding inward and outward inclined thin-walled parts with different offsets. The result shows that z-increment decreases gradually with offset increasing, the rate of reduction firstly increases then decreases, and when the offset AX is between0.06mm and0.08mm, the z-increment tsZ reaches its maximum decreasing rate. The single-layer utmost offset values for inclined thin-walled parts are obtained by inclination limit experiments. The inclination angles of inward and outward parts are close to the limit of40■. When the cladding parts reach the inclination limit, continuing increment of the offset or reduction of the z-increment will lead to the aggravation of the collapse of the cladding part and reduce the cladding height sharply.(3) The optimized cross-section paths are planed by simulating the process of forming arc-section inclined thin-walled parts through Matlab program. Using the arrays of offsets and z-increments obtained and the methods of varying z-increment and laser input energy, arc-section inward and outward inclined thin-walled parts with high geometrical precision and clad quality are successfully deposited. The arc-section inward inclined thin-walled part with136layers is formed using circle scanning path. The height of the part is16mm with the offset distance6.5mm, and the top slope angle is39.5o. The dimension errors of them are under0.78mm. After improving cooling measure and the method of transforming starting point, the arc-section outward inclined thin-walled part with124layers is formed using circle scanning path. The height of the part is15.5mm with the offset distance4.9mm.The results of the experiments demonstrate the feasibility of forming arc-section inclined thin-walled parts with the method of varying z-increment and laser input energy, which provides references for forming thin-walled parts with complex inclined structures.