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The alloy composition of Fe-Cr-Mo-C-B-Y-Co 7 components Fe-based alloy was selected as the master alloy and prepared by vacuum induction melting. Then the alloy ingots were re-melted and fabricated into spherical alloy powder by inert gas atomization process in the Material and Chemical Laboratories, Industrial Technology Research Institute (ITRI, Hsinchu). After size sieving, XRD analysis, and SEM examination, the atomized powders which can meet the specification of additive manufacturing were collected to do the linear laser melting test and cube selective laser melting (SLM) test. Hopefully, the optimum process parameters of SLM that is suitable for additive manufacturing can be designed.
After size sieving, the particle size of the most amount powder locates around 37~44 μm. According to the XRD results, all the powders which particle size below 63 μm are confirmed to be amorphous. On contrary, the structure of the powders with particle size more than 63 μm was found to contain an amorphous matrix co-existing with a C23C6, crystalline phase. The intensity of the C23C6 peak increases with increasing the powder size. Meanwhile, a spherical or near-spherical appearance can be clearly observed by SEM examination for all powders.
10 sets parameters of laser power and scanning rate were obtained from the results of linear laser melting test by OM observation. Then these 10 sets parameters and an additional parameter (which can successfully apply on produce maraging steel sample) were applied to do the cube SLM test. After SLM, cracks and spalls were found on the side view of most SLM cubes except the cubes made by the parameters of P240-S650 (#7), P240-S700(#8), and the parameter for maraging steel (#11). However, after the SEM examination on the cube samples made by parameters of #7, #8, and #11, respectively, there still can be found several unmelted powder particles on the surface of cube sample which made by the parameters of #8 and #11. In parallel, the laser melted powder layers of the cube sample made by # 11 parameter exhibit an insufficient fusion condition and the separated powder particles still can be seen on the side view of cube sample. Although there are no unmelted powder on the cube surface and no insufficient fusion condition on the side view for the cube sample made by #7 parameter, but there is one crack throughout the whole cube sample. On the other hand, there are only few unmelted powder particles on the sample surface, no clear separation of laser melted powder layers, and no obvious creaking can be found in the cube sample made by #8 parameter. Moreover, the cube sample made by parameter #8 presents higher hardness than the samples made by the parameters of #7 and #11, which means that the cube sample made by #8 parameter possesses higher product density than the other. In summary, #8 parameter seems the optimum process condition in this study and can be applied as the reference for the further laser additive manufacturing the Fe-based amorphous alloy.
Keyword: Fe-based metallic glass, atomization process, additive manufacture | en_US |