Study On The Technology Of Laser Additive And Subtractive Repairing Aluminium Alloy Casing

Laser additive and subtractive repairing technology is a new technology which combines traditional machining technology with advanced laser deposition repair technology to complete the integrated repair of parts.It effectively reduces the production cost and processing time.In this paper,the repaired technology of ZL114 A aluminium alloy is studied through the integrated test bench of CNC milling and laser deposition repair.Firstly,the basic repair process was studied according to the common damage of the casing,including the influence of different surface treatment methods to be repaired,the selection of the repairing angle of the opening groove,the effective corner of the laser powder feeding head,the selection of the material of the penetrating damage block and the repairing method of the thin bottom square groove.Secondly,for some special areas to be repaired,direct laser additive and subtractive repair can lead to the melting of parts or difficult to regularize.Cold welding process is needed as a transitional repair.Therefore,the research on cold-welding and cold-welding + laser deposition repair of pre-groove damage is carried out.The phase composition and component were tested,and the microstructure and mechanical properties of the repaired samples were contrastively analyzed.The results show that both repair processes can form a dense metallurgical bond,but the efficiency of cold welding repair is lower.The repaired area contains only Al and Si phases.The structure of the repaired area is composed of epitaxial columnar dendrites and Si phase between dendrites.The dendrite size of the laser deposited repair zone is about three times as large as that of the cold-welding repaired zone.The microhardness of the cold-welded repair zone is obviously higher,and the tensile strength of the repaired sample is both better than that of the repaired substrate.Finally,T6 heat treatment was carried out to further improve the mechanical properties of the repaired specimens.The phase composition,microstruture changes and the differences on the mechanical properties were compared.The results show that the compositions of the phases have not changed after T6 heat treatment,and the distribution of elements in the repair area is relatively uniform.The roundness of eutectic Si phases in the repair zone has been significantly improved.The eutectic Si phase distribution in the cold-welded repaired zone is more uniform,but the hardness was slightly lower due to the coarsening of Si phase.The average tensile strength of the repaired specimens reaches about 75% of the casting standard.