激光增材制造微小孔隙的射线成像及误差分析

X-ray Imaging and Error Analysis of Micro Pores during Laser Additive Manufacturing

通过激光选区熔化技术制备了GH3625高温合金制件,内部预制多个不同尺寸的孔隙。分别采用X射线数字成像和显微CT(Micro computed tomography, Micro-CT)对制件孔隙进行二维/三维表征。结果表明,对于直径为5 mm的GH3625高温合金SLM制件,在DR(Digital radiography)图像上能观察到全部直径设计值≥0.2 mm的预制孔隙,最小可检孔隙尺寸为0.18 mm。CT数据显示直径设计值为0.05 mm和0.1 mm的孔隙均未预制成功,直径设计值大于0.2 mm的孔隙全部预制成功,直径设计值为0.2 mm的孔隙中有两个未预制成功,其余全部预制成功,检测出的孔隙直径最小值为0.05 mm。结果表明,直径实测值大于设计值,绝对误差最大为0.26 mm,最小为0.03 mm。最后将不同位置的孔隙平移到基准位置,结合孔隙三维形貌,根据穿透厚度差,分析射线入射方向对不同孔隙成像的影响。

The GH3625 superalloy components were manufactured by selective laser melting(SLM), and multiple pores of different sizes were prefabricated in the interior. The pores of additive components were characterized in 2 D/3 D by X-ray digital radiography and micro-CT. The results indicate that for GH3625 superalloy SLM additive components with a diameter of 5 mm, prefabricated pores with a designed value of all diameters greater than or equal to 0.2 mm can be observed on DR images, and the minimum detectable pore size is 0.18 mm. CT data reveals that the pores with designed diameter of 0.05 mm and 0.1 mm are prefabricated to failure, while all the pores with designed diameter greater than 0.2 mm are successfully prefabricated. Among pores with design diameter of 0.2 mm, only the two are prefabricated to failure, and the rest are successfully prefabricated, and the minimum detected pore diameter is 0.05 mm. The results prove that the measured diameter value is greater than the designed one, with the maximum absolute error of 0.26 mm and the minimum of 0.03 mm. Finally, the pores at different positions were translated to the reference position, and the influence of the X-ray incident direction on the imaging of different pores was analyzed according to the penetration thickness difference combined with the three-dimensional morphology of the pores.