【作者】 李洪远；

【导师】 石世宏；

【作者基本信息】 苏州大学 ， 机械制造及其自动化， 2012， 硕士

【摘要】 激光熔覆快速成形技术是一种成形致密金属零件的新型制造方法。激光同轴送粉熔覆是该领域较成熟的工艺，但粉末利用率低（光外送粉利用率为20%-30%，光内送粉利用率为50%-80%），而采用金属丝进行熔覆时利用率可高达100%。本文针对送丝熔覆现状中的不足，采用了一种中空环形激光光内同轴送丝熔覆工艺，该工艺金属丝沿激光束中心线输送，保证丝与激光的同轴性。在现有光内同轴送丝光头的基础之上，设计一种更便于调节的光头，该装置通过调整环形聚焦镜来移动焦点的水平位置，实现金属丝与激光束的同轴耦合，由于采用光外调整方式，极大地提高了操作的安全性。利用设计的同轴送丝光头进行熔覆试验。研究了各个工艺参数对熔覆层表面形貌的影响，重点对离焦量、激光功率、扫描速度、送丝速度进行分析。试验结果表明：熔覆成连续熔道的前提是选一个合适的负离焦量；送丝速度对熔覆层截面宽高的影响最显著；工艺参数对熔覆层截面宽高的影响是相互的。通过正交设计优化了工艺参数，并通过扫描方向性试验证明了光内送丝熔覆能有效地消除扫描方向的问题。对工艺参数和熔覆层的宽高比关系进行了数学模型的建立，进行了统计检验和试验验证，通过因素的主效应分析得出：激光功率与熔覆层宽高比是正相关关系；送丝速度对宽高比的影响最显著，这与熔覆试验的结果分析是一致的。基于优化的工艺参数，进行了空心薄壁圆柱体的堆积，并对成形过程中离焦量和功率进行实时控制，最后得到的成形件表面质量较好、无坍塌、高度平整、微观组织晶粒细小、均匀，显微硬度值相对基体有明显提高而且分布均匀。更多还原

【Abstract】 Laser cladding rapid manufacturing (LCRM) is a novel manufacturing techniqueused to fabricate fully dense components. Feeding powder laser cladding process isquite mature in the field, but which powder utilization rate is low compared with thefeeding wire laser cladding process(outside laser coaxial-powder feeding utilization:20%-30%, internal laser coaxial-powder feeding utilization:50%-80%, laser wirefeeding utilization:100%). Aiming at the disadvantages of lateral wire feeding, anew inside-laser coaxial wire feeding process is adopted that can ensure a goodaxiality between wire and laser beam through transmitting wire along the centerlineof the laser beam.Base on the process of LCRM with coaxial inside-beam wire feeding, a morefacilitate adjustment device has been designed, which realizes the coaxial coupling ofthe wire and the laser beam by adjustting the annular focus lens to move the focus’level position and improves the safety of operation.The novel device was applied in the comparison experiments of laser claddingwith with different process parameters. The influences on the surface quality ofcrucial process parameters were investigated, such as laser power, scanning speed,wire delivery rate, defocusing amount and so on. Experimental results show that theprecondition of forming continuous cladding is to choose a suitable negative defocusdistance and the influence of wire delivery rate on cladding layer section’s width andheight is remarkable and the interaction of each process parameter influences thecladding layer section’s size. The optimum process parameters are selected throughorthogonal test and directional scanning experiment proves laser cladding withcoaxial inside-beam wire feeding can effectively eliminate the problem of scanningdirection.Mathematical modal is built for the relationship between process parameters andcladding layer section’s width and height with regression equation and statistical testswere carried out to verify the model. Through analyzing factors main effect, it isshown that laser power is positive relation with cladding layer section’s aspect ratio and the effect of wire delivery tate on cladding layer section’s aspect ratio. Themathematical model conclusion is consistent with the experimental analyses whichproves theoretical analyses correct.Based on the optimal process, a fine multy-layer hollow rotary parts was formedby keeping the defocus distance unchanged and adjusting the laser power in time.There are no subsidence damage and crack on the whole cladding layer. The widthand the thickness were uniform and the microstructure was uniformly distributed.The hardness of the laser cladding was uniformly distributed and larger than thesubstrate.更多还原