Abstract
The cold metal transfer plus pulse (CMT + P) process was performed to produce a 316L vertical wall through the single-channel multi-layer deposition method. The microstructure of different regions on deposited samples was observed by an optical microscope and a scanning electron microscope (SEM). The phase composition of the as-deposited wall was checked by X-ray diffraction, and the element distribution in the structure was analyzed by an energy-dispersive spectrometer. The tensile strength and microhardness of samples were tested, and the fracture morphology was observed by an SEM. Finally, the electrochemical corrosion characteristics of the as-deposited wall in different regions along the building direction were tested. Results from the experiments indicated that the microstructure of metallography showed a layer band. The metallurgical bounding between layers was carried out by dendrite remelting and epitaxial growth. Along the building direction, the alloy of different regions solidified in an ferritic-austenitic (FA) manner, and due to having undergone different heat histories, their SEM microstructures were significantly distinct. The ultimate tensile strength (UTS) and yield strength (YS) of the vertical specimens were higher than those of the horizontal specimens, displaying obvious anisotropy. Due to a large amount of precipitation of precipitated phases in terms of intermetallic compounds in the middle and upper regions, the tensile strength and microhardness along the building direction showed a trend of first decreasing and then increasing. In the bottom region, a small amount of ferrite precipitated in the austenite matrix, while in the middle of the as-deposited wall, the amount of ferrite gradually increased and was distributed in the austenite matrix as a network. However, due to the heat accumulation effect, the ferrite dissolved into austenite in large quantities and the austenite showed an obvious increase in size in the top region. A stable passivation film was caused by a relatively low dislocation density and grain boundary number, and the middle region of the arc as-deposited wall had the best corrosion resistance. The large consumption of chromium (Cr) atoms and material stripping in the top region resulted in the integrity of the passivation film in this region being the weakest, resulting in the lowest corrosion resistance.
Highlights
Traditional machine part manufacturing methods mainly rely on casting and forging [1]
3b, it can be seen that the weld bead was clear and straight, and no metal flow or collapse observed on the surface of the as-deposited wall, which shows good adaptability of the CMT was observed thestainless-steel surface of theWAAM
In the results indicate that the single-channel multilayer continuous arc-welding deposition addition, the fracture of specimen V2 had a large number of deeper dimples than those on specimen process beduring appliedthe to the additive manufacturing ofspecimen, 316L stainless steel. load acceptor was
Summary
Traditional machine part manufacturing methods mainly rely on casting and forging [1]. Most of the current wire arc additive manufacturing (WAAM) research is generally based on the traditional pulse current as the arc source, and the range of research mainly focuses on studying the influence of various process parameters such as current, voltage, and welding speed on molding appearance and mechanical properties [7,8,9]. Another popular manufacturing process is powder bed fusion, where the molten alloy is formed by melting powder form in a capillary flow in micropores. The microstructure of castings usually contains porosity and inclusions, which may negatively affect the mechanical properties of the workpiece
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