Additive Manufacturing of WC-Co Specimens with Internal Channels

Abstract

Most material removal in modern manufacturing is currently performed using tools with indexable inserts. Additive manufacturing allows for the creation of new, experimental insert shapes and, more importantly, internal structures, such as channels for coolant. This study deals with developing a process for efficiently manufacturing WC-Co specimens with internal coolant channels with a focus on obtaining a suitable microstructure and surface finish, especially inside the channels. The first part of this study covers the development of process parameters to achieve a microstructure without cracks and with minimal porosity. The next stage focuses solely on improving the surface quality of the parts. Special attention is given to the internal channels, where true surface area and surface quality are evaluated, as these characteristics greatly influence coolant flow. To conclude, WC-Co specimens were successfully manufactured and a microstructure with low porosity and no cracks was achieved and an effective parameter set was found. We have developed a process that produces parts with a surface roughness comparable to those of standard SLS manufacturing of steel parts, while still providing a high-quality internal microstructure. The most suitable parameter set resulted in a profile surface roughness of Ra 4 μm and Rz 31 μm and areal surface roughness of Sa 7 µm and Sz 125 µm.

Effect of Post-Fabrication Heat Treatments on the Microstructure of WC-12Co Direct Energy Depositions

“…Internal cracks are common defects that appear in AM components, especially in WC-Co materials, usually due to the development of high thermal stresses during the process. Hence, their occurrence must be controlled [13,[28][29][30][31][32]. Some research demonstrated that these stresses are generated during solidification [33,34].…”

Material Extrusion to Manufacture Carbide-Based Advanced Cutting Tools

“…For the last ten years, there has been an increase in the research on AM with respect to tungsten carbide and cermets [4][5][6]. They have been tested with powder bed fusion (PBF) [7][8][9][10][11][12][13][14], binder jetting (BJT) [15][16][17], material extrusion (MEX) [18][19][20][21][22][23][24], and vat photopolymerization (VPP) [25]. Although they still underperform compared to the pressing and sintering method [26,27], they still possess advantages related to design freedom, which can justify the use of AM for certain applications.…”

“…In this process, heating and cooling rates are extremely fast [7,12], and particularly high energy outputs are needed to achieve sintering temperatures. In hardmetals and cermets, the high temperatures, which are reached in the center of the energy beam, are well above the melting temperature of cobalt; this entails evaporation during the consolidation process, which results in the embrittlement of the material [7,8,10,[12][13][14]. The heating/cooling thermal cycles are so fast that the thermal shock induced is enough to result in the development of cracks and delamination [9].…”