Abstract
This paper examines different blends of starting materials for alloy development in the laser powder bed fusion (LPBF) process. By using blends of individual elemental, ferroalloy and carbide powders instead of a pre-alloyed gas-atomized starting powder, elaborate gas-atomization processes for the production of individual starting powders with varying alloy compositions can be omitted. In this work the model alloy Fe3.5Si1.5C is produced by LPBF from different blends of pure elemental, binary and ternary powders. Three powder blends were processed. The base material for all powder blends is a commercial gas-atomized Fe powder. In the first blend this Fe powder is admixed with SiC, in the second with the ternary raw alloy FeSiC and in the third with FeSi and FeC. After characterizing the powder properties and performing LPBF parameter studies for each powder blend, the microstructures and the mechanical properties of the LPBF-manufactured samples were analyzed. Therefore, investigations were carried out by scanning electron microscopy, wave length dispersive x-ray spectroscopy and micro hardness testing. It was shown that the admixed SiC dissolves completely during LPBF. But the obtained microstructure consisting of bainite, martensite, ferrite and retained austenite is inhomogeneous. The use of the lower melting ferroalloys FeSi and FeC as well as the ternary ferroalloy FeSiC leads to an increased chemical homogeneity after LPBF-processing. However, the particle size of the used components plays a decisive role for the dissolution behavior in LPBF.
Highlights
The model alloy composition to be obtained after Laser Powder Bed Fusion (LPBF) processing will be referred to as target alloy and the raw materials used for blending are defined as raw alloys
The FeSiC system is a basic system for steels and cast irons and was chosen as a target alloy, due to several specific limitations and possibilities regarding phase and microstructure evolution in the LPBF process
Bigger particles may not dissolve during the short residence tion process at the phase boundaries, inhomogeneous element distribution or incomtime of the melt pool during LPBF processing
Summary
Individual metal powder alloys for Laser Additive Manufacturing (LAM). Processes such as Laser Powder Bed Fusion (LPBF) are difficult to achieve due to the complex LPBF processability and the complicated atomization process. Only few alloys can be found in the market. Laser additive manufacturing is an emerging technology offering a variety of different process-related advantages compared to subtractive manufacturing. LPBF uses a powder feedstock, which is deposited on a building platform and selectively fused by a computer-controlled laser beam under an inert gas atmosphere [1,2]
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