Selective laser melting (SLM), as one of the additive manufacturing technologies, is widely investigated to fabricate metal parts. In SLM, parts are manufactured directly from powders in a layer-by-layer fashion; SLM also provides several advantages, such as production of complex parts with high three-dimensional accuracy, compared with other additive manufacturing technologies. Therefore, SLM can be applied in aeronautics, astronautics, medicine, and die and mould industry. However, this technique differs from traditional methods, such as casting and forging; for instance, the former greatly differs in terms of microstructure and properties of products. This paper summarizes relevant studies on metal material fabrication through SLM. Based on a work completed in Huazhong Univ. Sci Tech., Rapid Manuf. Center (HUST-RMC) and compared with characteristics described in other reported studies, microstructure, properties, dimensional accuracy, and application of SLM are presented.

Differences in microstructure and properties between selective laser melting and traditional manufacturing for fabrication of metal parts: A review

Selective laser sintering (SLS) is an additive manufacturing technology which has shown great advantages in direct formation of the polymer, metal and their composites. However, ceramic parts prepa...

High-performance ceramic parts with complex shape prepared by selective laser sintering: a review

Three-dimensional (3D) printing technology is becoming a promising method for fabricating highly complex ceramics owing to the arbitrary design and the infinite combination of materials Insufficient density is one of the main problems with 3D printed ceramics, but concentrated descriptions of making dense ceramics are scarce This review specifically introduces the principles of the four 3D printing technologies and focuses on the parameters of each technology that affect the densification of 3D printed ceramics, such as the performance of raw materials and the interaction between energy and materials The technical challenges and suggestions about how to achieve higher ceramic density are presented subsequently The goal of the presented work is to comprehend the roles of critical parameters in the subsequent 3D printing process to prepare dense ceramics that can meet the practical applications

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Dense ceramics with complex shape fabricated by 3D printing: A review

In this study, bulk net-shape pure magnesium was fabricated by selective laser melting (SLM). Effects of Mg particle size and processing parameters on the properties of SLM specimens were investigated. The scan speed and laser power were optimized based on macro-observation of the forming process and resulted specimens. Through the comparison analysis of topology, density, and micro-hardness, it was found that the bulk magnesium specimen made of −250 mesh powder showed better results than that made of −400 mesh powder. The relative densities of both SLM specimens were over 95%, and their micro-hardness values were higher than that of as-cast magnesium. It was also revealed that the scanning time interval (STI), as a relatively new processing parameter, had an obvious effect on the properties of SLM bulk magnesium in terms of surface morphology, roughness, and micro-hardness.

Experimental Investigation on Selective Laser Melting of Bulk Net-Shape Pure Magnesium

Blending Polyetheretherketone (PEEK) with Polyvinyl alcohol (PVA) is promising to obtain a composite scaffold combining the excellent biomechanical properties of PEEK and the remarkable degradabili...

Graphene oxide-driven interfacial coupling in laser 3D printed PEEK/PVA scaffolds for bone regeneration

Indirect selective laser sintering of epoxy resin-Al2O3 ceramic powders combined with cold isostatic pressing

The porcelain fracture caused by low metal-ceramic bond strength is a critical issue in porcelain fused to metal(PFM) restorations. Surface roughening methods, such as sand blasting, acid etching and alkaline degreasing for the metal matrix are used to increase bond strength. However, the metal matrix of PFM processed by selective laser melting(SLM) has natural rough surface. To explore the effect of the original roughness on metal-ceramic bond strength, two groups of specimen are fabricated by SLM. One group of specimen surface is polished smooth while another group remains the original rough surface. The dental porcelain is fused to the specimens’ surfaces according to the ISO 9693:1999 standard. To gain the bond strength, a three-point bending test is carried out and X ray energy spectrum analysis(EDS), scanning electron microscope(SEM) are used to show fracture mode. The results show that the mean bond strength is 116.5 ± 16 MPa of the group with rough surface(R
 a=17.2), and the fracture mode is cohesive. However, when the surface is smooth (R
 a=3.8), the mean bond strength is 74.5 MPa ± 5 MPa and the fracture mode is mixed. The original surface with prominent structures formed by the partly melted powder particles, not only increases surface roughness but also significantly improves the bond strength by forming strong mechanical lock effect. Statistical analysis (Student’s t-test) demonstrates a significant difference (p<0.05) of the mean value of bond strength between the two groups. The experiments indicate the natural rough surface can enhance the metal-ceramic bond strength to over four times the minimum value (25 MPa) of the ISO 9693:1999 standard. It is found that the natural rough surface of SLM-made PFM can eliminate the porcelain collapse defect produced by traditional casting method in PFM restorations.

Liang Hao

Papers

Indirect selective laser sintering of epoxy resin-Al2O3 ceramic powders combined with cold isostatic pressing

Metal-ceramic bond mechanism of the Co-Cr alloy denture with original rough surface produced by selective laser melting