马氏体时效钢激光增材制造工艺及组织研究

Maraging Steel Laser Additive Manufacturing Process and Microstructure Study

探究了使用同轴送粉激光直接沉积增材制造方法制造18Ni(300)马氏体时效钢零件的可行性。采用正交实验设计,分析了不同工艺参数对单道成形的影响,发现扫描速度、送粉速率、激光功率对稀释率的影响较大。在单道多层试验中发现在合适的参数下18Ni(300)能获得良好的外观成形,但内部仍然容易出现非致密性缺陷。激光直接沉积制造过程的高冷却速率使得晶粒最小可以达到8μm,晶粒生长方向大致与散热方向相同,但在层间位置存在晶粒转向区,而在顶部存在柱状晶/等轴晶转变区。在扫描电镜下发现由于加工过程中热循环的特点,先沉积层出现了析出相造成了硬度值的变化。硬度试验发现,越靠近基材的硬度值越高,最高可达358HV。

The 18Ni（300） coaxial laser direct energy deposition process was studied.firstly,orthogonal test was designed,and the influence of different parameters to single-layer-single-trace forming appearance were analyzed,it was found that scanning speed,powder feed rate,laser power had greater impact.Although maraging steel could obtain good forming appearance under appropriate parameters,the workpiece was still prone to have internal defects such aspores,which was found in single-tracemulti-layer experiments.Because of the high cooling rate of the process,minimum crystal grain could reach 8 μm.The grain grew along the heat radiation direction,but shift grains presented in the interlayer region,and columnar grains changed to equiaxed grains at the top part.Higher hardness values were found closer to the substrate by micro-hardness test,the highest value was 358 HV.It was found that the emergence of precipitates caused by the thermal cycle led to the changes of hardness,which was found by scanning electron microscopy.