Investigation of LPBF A800H steel parts using Computed Tomography and Mossbauer spectroscopy

Laser powder bed fusion (LPBF) was applied in this study to produce a prototype of a miniaturized catalytic burner (CAB), which is a key component of high-temperature polymer electrolyte fuel cells. This prototype was characterized by its complex design with numerous channels, chambers, and thin walls. The test samples and CAB prototype were made of a heat-resistant, anti-corrodible steel called "Alloy 800H" (1.4876), a material that poses problems for welding operations and especially for the LPBF process due to its strong susceptibility to hot cracking and spatters. The effects of LPBF parameter variation on preliminary test samples were investigated by nano-focus Computed Tomography (CT) and Optical microscopy to clarify the internal structure and defects for further LPBF process optimization. Mossbauer spectroscopy points out that LPBF process does not lead to either local phase separation nor oxidation of steel, which is critical factor for use of CAB at high temperatures. The sufficient LPBF parameter sets were used to manufacture the CAB prototype, which was examined by micro-CT and optics as well. The main result of the investigation is a demonstration of the technological feasibility to decrease the number and size of defects in complex LPBF-manufactured Alloy 800H constructions without changes in phase composition at high temperatures.