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利用数值分析和试验相结合的办法,对多道搭接激光熔覆层的开裂机理和规律进行了研究。数值分析结果表明,激光熔覆后,熔覆层内部呈明显的拉应力状态,且主要集中在熔覆层底部与基体的交界处,因此单道熔覆时熔覆层的开裂倾向主要是垂直于扫描方向。在两道搭接熔覆时,前一次熔覆输入试样的激光能量在试样内部传递和扩散已有一定的时间,试样的整体温度升高后,第二次熔覆时激光能量输入产生的热量在试样内部形成的温度梯度就会有所减小,从而降低了工件内部的应力水平。两道熔覆完成后,由于熔覆层在扫描所受的拉应力降低的幅度最大,而垂直于扫描方向所受的拉应力变化不大,此时若熔覆层开裂,则开裂的方向将不再是垂直于扫描方向,而是会与扫描方向成一定的夹角。实际熔覆中,对单道、多道熔覆时熔覆层的开裂现象进行了观察,试验结果与分析结果较好地吻合。
The cracking mechanism and rule of lap lapping cladding layer were studied by the combination of numerical analysis and experiment. The results of numerical analysis show that the laser cladding has obvious tensile stress in the cladding and mainly concentrates on the interface between the cladding and the substrate. Therefore, the cracking tendency of the cladding is mainly vertical In the scanning direction. In the lap welding, the laser energy of the previous cladding input sample has been transmitted and diffused within the sample for a certain period of time. After the overall temperature of the sample is increased, the laser energy input of the second cladding The heat generated within the sample will be formed within the temperature gradient will be reduced, thereby reducing the stress level within the workpiece. After the two cladding is completed, the tensile stress suffered by the cladding layer decreases to the maximum while the tensile stress perpendicular to the scanning direction does not change much. In this case, if the cladding layer is cracked, the direction of cracking will be No longer perpendicular to the scanning direction, but with the scanning direction into a certain angle. In the actual cladding, the phenomenon of cracking of the cladding layer during single-pass and multi-pass cladding was observed. The experimental results were in good agreement with the analysis results.