Key Technology Of Additive And Subtractive Manufacturing Based On Pulsed Laser Wire Deposition

Industrial technology can always develop along the path from preliminary research by lab,improvement of the process,to leading products application,and finally mass application.Metal additive manufacturing(AM)is also a kind of developing technology urgently to be study and pushed to the market.In China,from the main bearing component of the aircraft,to the precision instrument base of the inertial navigation system,there exist great demand for the potential technology,and this as well is the main driven force in the development of AM in China.Yet the progress of AM development in China seems to be difficult since the unsubstantial industrial fundation.Particularly,the reliabiligy of the equipment and process,as well as the mechanisms of accuracy and mechanical property of AM-made products are in urgent need of deeply understanding.Besides,products with precision surface,complex narrow slit and inner chamber can hardly be fabricated by single AM process.For these kinds of products,a novel hybrid AM technology is needed,and actually,this is an emergent requirement because most of the products in the airocraft and inertial navigation system are complex and precise.In the current research,we proposed a novel additive and subtractive manufacturing technnology besed on pulsed laser wire deposition.By combining the pulsed laser wire deposition and metal cutting technique,we aims to explore a solution that can meet the requirement in both accuracy and mechanical property.First,we develop the hybrid additive and subtractive manufacturing machine tool according to the design requirements,on which several key technology is studied.Preliminary process study of the hybrid machine tool.In this part,the basic functions of the hybrid machnie tool are validated,such as deposition and cutting.During the research,we obtain the relation between process parameters and deposited shape,as well as process sensibility.Further,the process map is drew to guide the direction of process optimization.Results in this part are the foundation of the following works.Microstructure evolution of the pulsed laser wire deposition.During this part of research,a thin wall and step block are designed and fabricated for study.Additionally,the global temperature field and local fluid field are simulated using finite element method.In the reference of alloy phase diagram,the microstructure evolution both of the thin wall and the step block are studied in details.Defects and their propagation in the parts fabricated by pulsed laser wire deposition.At first,the defects are clarified according to their formation character,and then the formation and propagation mechanisms of these defects are analyzed.For further understanding of the pore and crack formation,a novel heat source model is established,and both the heating and cooling stage are calculated.Results are discussed to explain the influence of local temperture gradient and local stress on defect formation and propagation.Process research of the hybrid additive and subtractive manufacturing.Interactional relationships between depositing and cutting are studied unidirectionally first,and the optimized process parameters are chosen to implement the bidirectional research.Finally,the influence of succesive fabrication process on thin wall accuracy and the microstructure are discussed.Exploration on rapid solidification in pulsed laser processing.A kind of inert gas high-pressure aided laser processed method is proposed,and the impact of high gas pressure on rapid solidification are researched.Besides,ultrasonic aided AM is explored,and the action mechanism of ultrasonic on solidification is revealed.With deeply researches on the above key technology of pulsed laser wire deposition based additive and subtractive manufacturing,we verify that the proposed process is feasible to make complex and precision products.Results indicate that grain size of 1~1.5?m can be obtained,and the surface roughness after cutting is below Ra6.3,in addition,no macro deformation is detected.In conclusion,we proposed a novel additive and subtractive manufacturing technology based on pulsed laser wire deposition,and the whole work have provided a new solution for precision and complex products,and have laid a theoretical foundation process guidance for the research of AM.