Research of Surface Roughness and Relative Density of SLM Medical Co-Cr Alloy

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.

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Section: 引言激光选区熔化(Slm)是一种基于激光熔化金属粉末的快速成型技术，成型原理是将设计的三维模型离散unclassified

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

Shuzhen¹,

Yongqiang²,

Di³

2015

中国激光

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Ultrasonic Measurement of Stress in SLM 316L Stainless Steel Forming Parts Manufactured Using Different Scanning Strategies

2019

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Selective Laser Melting (SLM) technology is a new kind of additive manufacturing technology developed in in the last decade. Measurement and control of stress in metal forming layer is the basic problem of SLM forming parts. Critical Refraction Longitudinal (LCR) wave method was used to measure stress. The acoustic-elastic formulas for measuring stresses in SLM 316L stainless steel forming parts manufactured using meander, stripe, and chess board scanning strategies, respectively, were established based on static load tensile test. The experimental results show that the acoustic time difference of LCR wave in SLM specimen manufactured with 316L stainless steel increases linearly with the increase of stress when the tensile stress is less than critical stress (372 MPa, 465 MPa, and 494 MPa). Due to the inhomogeneous deformation of the anisotropic SLM forming layer and the dimple-micropore aggregation fracture mechanism, the acousto-elastic curve fluctuates up and down along the irregular curve when the tensile stress is larger than critical stress. The results of corroboration experiments show that nondestructive measurement of stress in SLM forming specimen can be realized by using LCR wave method. The scanning strategy can significantly affect the tensile strength and yield strength of SLM forming specimen. The stresses were all in tension stress state at the edge of the specimens, whatever scanning strategy was used. Sub-area scanning and scanning sequence of alternate and intersect were adopted, which can effectively reduce the stress in the SLM forming specimen. The overall stress values of SLM forming specimen manufactured using chess board scanning strategy were smaller than that using meander and stripe strategies. The distribution of stress were more uniform.

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Research on Surface Roughness of AlSi10Mg Parts Fabricated by Laser Powder Bed Fusion

Bai

et al. 2018

Metals

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AlSi10Mg cubes were fabricated with the laser powder bed fusion (LPBF) process, using different exposure times and scan strategies to gain insight into the effect of energy density and part orientation on surface roughness. The results showed that, with increasing energy density, the five-face roughness first decreased and then increased, whereas the top roughness increased slightly. Moreover, considerable differences in roughness appeared for the different faces. A good surface quality was obtained at 175 J/mm 3 and 200 J/mm 3 when the rotation start angle and rotation increment angle were set as 0 in meander scan mode. The roughness variation was caused by the scan direction, gas flow direction, and wiper movement direction. The scan strategies with rotation increments of 90 • effectively narrowed the variation. These results support direct part orientation and placement and can guide users to further reduce roughness through process optimisation or simplification of post-processing procedures.

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Research of Surface Roughness and Relative Density of SLM Medical Co-Cr Alloy

Cited by 3 publications

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

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

Ultrasonic Measurement of Stress in SLM 316L Stainless Steel Forming Parts Manufactured Using Different Scanning Strategies

Research on Surface Roughness of AlSi10Mg Parts Fabricated by Laser Powder Bed Fusion

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