Research On Laser Additive Manufacturing Characeristics Of Titanium Alloy With Powder And Wire

As one of the most common and most widely used titanium alloy, the usage of TC4has accounted for more than50%of the titanium all over the world. Traditionalmanufacturing technology of titanium alloy exists many shortcomings, such as prone tostick a knife and the phenomenon of tool wear, requiring large forging equipments, longproduction cycle, the material utilization is low and the manufacturing costs are high.Moreover, it is difficult to manufacture complex shape parts. Laser additivemanufacturing, also known as laser3D printing, is a layer-by-layer technique ofproducing three-dimensional (3D) objects directly from a digital model. Which providesa low-cost, short-cycle approach for the manufacturing of titanium alloy.This paper mainly adopts coaxial powder feeding and paraxial wire feeding toresearch the laser additive manufacturing of TC4. The forming characteristics of the twomethods, microstructures, mechanical properties and other aspects were studied, also,the influence of heat treatment process on the microstructure and mechanical propertiesof forming parts was studied. Finally the two methods are compared.Through single forming process research, analyzed the influence of processparameters on the size of single-shaping and the range of process parameters wereobtained; Multilayer forming process showed that the protective atmosphere has a greatinfluence on the laser additive manufacturing of TC4. Research is mainly focused on themechanism of directional columnar crystal, puts forward the corresponding controlmethods; The mechanical properties were tested, indicating that deposited TC4with acharacteristic of high strength and low toughness.The microstructures of the deposited TC4are analyzed by optical metalloscope andSEM, which are mainly directional growth of coarse β columnar grain through multiplelayers. And it is full of widmanst tten structure, at the same time, the parallel layerbands were also found. Analyzed the relationship between microstructures andproperties, explained the mechanism of widmanst tten and the layer bands formation;Analyzed the evolution of the microstructure and mechanical properties after heattreatment.The paraxial wire feeding method has some outstanding technological difficulties,such as the neutral between laser and wire, oxidation protection, spheroidization of droplet, incomplete fusion between layers etc. Which were resolved by the equipmentimprovement and process optimization. Studied the influences of process parameters insingle layer forming size, and compared with the powder feeding type. From processcontrol, microstructure characteristics and performance evaluation，the multilayerforming characteristics were studied. Compared the advantages and disadvantages ofthe two methods in process window and internal defects, microstructure, mechanicalproperties, dimensional precision and surface accuracy, efficiency and economy etc.