激光选区熔化成型NiCr合金曲面表面形貌及粗糙度变化规律研究

Study on Surface Morphology and Roughness Variation of NiCr Alloy Curved Surface Manufactured by Selective Laser Melting

为快速直接制造具有复杂曲面的个性化金属零件,需要保证激光选区熔化(SLM)成型曲面特征的表面成型质量。通过正交实验获得Ni Cr合金优化工艺参数,采用S型正交层错扫描策略成型两种柱面体模型;在超景深显微镜、扫描电镜下观察成型件内、外侧曲面表面形貌,并测量相应表面粗糙度。结果表明:成型不同空间位置摆放的曲面零件,各层面轮廓误差、层面间台阶效应的逐层堆叠最终使曲面形成台阶状、网结状形貌,成型倾斜切角小于60°的悬垂曲面时因粉末粘附严重甚至会形成条虫状、粒球状形貌;表面粗糙度Ra值与曲面特征表面形貌变化规律具有相关性,这为提高SLM成型曲面零件的表面成型质量提供了重要参考。

In order to directly fabricate customized metallic parts with complicated surface, the surface quality of curved surface feature manufactured by selective laser melting （SLM） technology should be ensured. The parameters of NiCr alloy are optimized by orthogonal experiment and two kinds of cylinders are fabricated with X-Y inter-layer staggered scan strategy. The surface morphologies of curved surfaces of the parts are studied using three dimensional super depth digital microscope and scanning electron microscope, and the corresponding surface roughness is measured. The results show that when fabricating the parts with curved surface placed in different spatial positions, contour error in layer and stair effect among layers stacked lead to the staircase-shaped profile and anastomosing morphology on curved surfaces, and even the worm-like or granular morphology on overhanging curved surfaces when the tilt angle is larger than 60°. Variation of the value of Ra is consistent with surface morphology. The results provide important guidance to improve surface quality of the parts with curved surface fabricated by SLM.