沉积效率对激光近净成形316L不锈钢组织及性能的影响

利用激光近净成形技术进行了316L不锈钢单道多层结构的制备。在相同的激光功率及扫描速度条件下，通过调整送粉率及层间提升量实现了不同沉积效率的成形，并讨论了不同沉积效率下成形结构的微观组织及力学性能特征。结果表明，在一定的激光功率及扫描速度条件下，随着送粉率及层间提升量的提升，沉积效率由初始工艺参数条件下的12.14 mm3/s提高至22.62 mm3/s，提高了86.3%。同时成形单位有效体积消耗的激光能量由初始工艺参数条件下的98.84 J/ mm3降低至53.06 J/mm3，能量利用效率提高了46.32%。成形结构的微观组织呈柱状枝晶形态，随着沉积效率的提高，枝晶长度呈明显的增大趋势。性能检测结果显示，不同沉积效率下的样件力学性能保持了较高的一致性，并未随沉积效率的提高而降低，成形样件抗拉强度及屈服强度分别稳定在510 MPa与290 MPa，延伸率稳定在40%左右，显微硬度也未出现明显波动，处于180 HV，均达到了锻造的同等水平。该研究表明，在一定的工艺参数范围内，可以实现沉积效率及力学性能的协同优化，达到低能耗高效制备高性能零件的效果。

Effect of deposition efficiency on microstructure and property of 316L stainless steel fabricated by laser engineered net shaping

Laser engineered net shaping is a promising technique to fabricate high-performance components with complex geometry rapidly. Excellent properties of fabricated specimen and high deposition efficiency are both important for this additive manufacturing method, but few researches have been done on the relationship between them. In this paper, single-bead multilayer structures of 316L stainless steel are fabricated by laser engineered net shaping (LENS). Using the same laser power and scanning speed, different deposition efficiencies are achieved by adjusting powder flow rate and layer increment. Microstructures and mechanical properties of the deposited structures under different deposition efficiencies are discussed. The results show that, for certain laser power and scanning speed, the deposition efficiency increases from 12.41 mm3/s to 22.62 mm3/s with the increase of the powder flow rate and layer increment, which increases by 86.3% compared with the initial process. Laser energy consumed by depositing unit effective volume reduces from initial 98.84 J/mm3 to 53.06 J/mm3 and the energy efficiency increases by 46.32%. Microstructures of the specimen consist of columnar dendrite and the dendrite length increases obviously with the deposition efficiency. Property test shows that properties of the specimen under different deposition efficiencies are consistent and do not decrease with the deposition efficiency. Tensile strength and yield strength are stable in 510 MPa and 290 MPa, respectively. The elongation rate is around 40% while the micro-hardness is about 180 HV, all of which have reached the same level of forging. The results illustrate that the deposition efficiency and mechanical property can be optimized, which achieves fabrication of high performance parts with low energy consumption and high efficiency.