Assessment of Usability of WC-Co Powder Mixtures for SLM

The study focuses on microstructural evolution in a WC-Co powder mixture during Selective Laser Melting (SLM) and hot isostatic pressing (HIP) processing. This powder mixture contained a 13 ± 0.6% weight fraction of Co binder and WC particles of mean size of 3.0 ± 1.9 μm. SLM of the mixture produced samples of various densities, depending on the volumetric energy density (VED) applied. High VED levels led to densities of up to 88%. The aspects affected by changes in VED included the pore density as well as the resulting types of phases and the size of WC phase particles. At high VED, the material began to develop cracks due to embrittlement. This had multiple causes: coarsening of α-phase (WC), evaporation of β-phase (Co binder), and precipitation of η-phase. At low VED levels, pores formed, typically of nonsymmetric shapes, with sizes larger than 500 μm. Subsequent HIP processing led to an increased density, up to 96% of solid material. Contributions to this increased density were provided by structure transformations, namely, coarsening of α-phase by up to 1300% when compared to the powder grain size, and formation of η-phase. The results provided a basis for steering further research to explore to a greater depth the SLM and HIP processing of selected WC-Co powder mixtures with as yet unused ranges of process parameters.

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“…EDS analysis found that the particles contain 13 ± 0.6 wt.% of Co binder. The particle size of α-phase was 3.0 ± 1.9 µm [36,37].…”

Section: Experimental Materialsmentioning

confidence: 99%

Development of the Structure of Cemented Carbides during Their Processing by SLM and HIP

Bricín

Ackermann

Jansa

et al. 2020

Metals

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“…In the sample with 6 wt.% Co content, a W 2 C phase was formed [116]. The common WC-Co samples prepared by SLM do not contain more than 20 wt.% Co, and ternary and W 2 C phases are generally formed in these samples [111].…”

Section: Microstructurementioning

confidence: 99%

“…For the AM processes that require a powder spreading step, including the above three, powder properties, most importantly the flowability, are critical to the success [110]. In SLM and BJAM without an infiltration process, WC-Co powders need to be pre-alloyed before printing [78,111]. In the BJAM process that requires infiltration, WC powder is used directly [76].…”

Section: Slm and Sebmmentioning

confidence: 99%

“…In the BJAM process that requires infiltration, WC powder is used directly [76]. Regardless of whether it is WC-Co powder or WC powder, the particle size will affect the fluidity, and 10 to 50 μm is a suitable size [78,111]. The powder should be spherical and free of surface defects because the irregular topography and defects can impair the flowability of the powder [112].…”

Section: Slm and Sebmmentioning

confidence: 99%

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Additive manufacturing of WC-Co hardmetals: a review

Yang

Zhang

Wang

et al. 2020

Int J Adv Manuf Technol

112

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WC-Co hardmetals are widely used in wear-resistant parts, cutting tools, molds, and mining parts, owing to the combination of high hardness and high toughness. WC-Co hardmetal parts are usually produced by casting and powder metallurgy, which cannot manufacture parts with complex geometries and often require post-processing such as machining. Additive manufacturing (AM) technologies are able to fabricate parts with high geometric complexity and reduce post-processing. Therefore, additive manufacturing of WC-Co hardmetals has been widely studied in recent years. In this article, the current status of additive manufacturing of WC-Co hardmetals is reviewed. The advantages and disadvantages of different AM processes used for producing WC-Co parts, including selective laser melting (SLM), selective electron beam melting (SEBM), binder jet additive manufacturing (BJAM), 3D gel-printing (3DGP), and fused filament fabrication (FFF) are discussed. The studies on microstructures, defects, and mechanical properties of WC-Co parts manufactured by different AM processes are reviewed. Finally, the remaining challenges in additive manufacturing of WC-Co hardmetals are pointed out and suggestions on future research are discussed.

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“…The quality of samples and parts built with laser powder bed fusion is strongly influenced by the properties of the metal powders particles themselves [30,55,56], as also outlined by official regulation agencies such as ASTM (ASTMF2924-14 [29]). Granulometry, flowability, particle size, density, and chemical composition are among the most crucial properties which are typically checked before processing the selected powder [47,[57][58][59][60][61].…”

Section: Powder Feedstock Featuresmentioning

confidence: 99%

Material Reuse in Laser Powder Bed Fusion: Side Effects of the Laser—Metal Powder Interaction

Santecchia

Spigarelli

Cabibbo

2020

Metals

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Metal additive manufacturing is changing the way in which engineers and designers model the production of three-dimensional (3D) objects, with rapid growth seen in recent years. Laser powder bed fusion (LPBF) is the most used metal additive manufacturing technique, and it is based on the efficient interaction between a high-energy laser and a metal powder feedstock. To make LPBF more cost-efficient and environmentally friendly, it is of paramount importance to recycle (reuse) the unfused powder from a build job. However, since the laser-powder interaction involves complex physics phenomena and generates by-products which might affect the integrity of the feedstock and the final build part, a better understanding of the overall process should be attained. The present review paper is focused on the clarification of the interaction between laser and metal powder, with a strong focus on its side effects. Figure 1. Schematics of the laser powder bed fusion (LPBF) equipment. Adapted from Reference [9] with permission from Elsevier.While the market and the applications of laser powder bed fusion continuously and impressively grew in recent years, there is a common view across users and researchers concerning the repeatability of the process in terms of chemical composition and mechanical properties of the final parts, which are of paramount importance when challenging environmental or testing conditions are considered [10][11][12][13][14][15][16].The most typical approach to study the microstructural and mechanical properties of parts built by LPBF is to compare them with castings of the same alloy or, rather, the corresponding alloy since the starting material is metal powder rather than a fuse. However, in some existing alloys designed for cast and wrought parts, laser additive manufacturing processing results in cracking or other microstructure deficiencies [11,12,16,17]. It is worth noting that LPBF has more similarities with laser welding rather than casting, since the two laser-based techniques have some common features (i.e., melt-pool formation, moving heat source) [18]. However, process parameters are, in general, quite different in terms of laser power and scan speed, and the laser-matter interaction is much more complicated in LPBF processes, since the powder feedstock is inherently unstable and the solidified material undergoes multiple thermal cycles corresponding to the fusion of subsequent layers during the additive process [19][20][21][22]. Furthermore, owing to the similarities with welding and to the complicated interaction between laser and metal particles, when comparing laser powder bed fusion with other metal forming processes, it is evident that the range of processable alloys is very limited and the number of high-productivity commercially available alloys is even smaller [23]. One of the reasons behind this is that the level of metal powder sensitivity to the laser action during LPBF is not yet fully understood, despite the efforts of the scientific community to uncover it [24][25][26][27], and ...

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Assessment of Usability of WC-Co Powder Mixtures for SLM

Cited by 9 publications

References 5 publications

Development of the Structure of Cemented Carbides during Their Processing by SLM and HIP

Development of the Structure of Cemented Carbides during Their Processing by SLM and HIP

Additive manufacturing of WC-Co hardmetals: a review

Material Reuse in Laser Powder Bed Fusion: Side Effects of the Laser—Metal Powder Interaction

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