Speaker
Description
Molybdenum is a difficult-to-weld metal that, when processed by Powder Bed Fusion – Laser Beam (PBF-LB/M) is prone to cracking and residual porosity. This presentation addresses the crucial role of oxygen impurities driving the formation of such defects and the beneficial effects that can be exploited by utilizing carbon as an alloying element.
The effects of these two elements on manufacturing temperature, solidification mechanism, and grain boundary strength, are discussed. It was found that oxygen is responsible for the cracks in PBF-LB of molybdenum regardless of the processing temperature. Alloying molybdenum with 0.45 wt.% carbon diminishes the detrimental effects of oxygen by three effects: Firstly, outgassing of carbon monoxide, secondly by enabling grain refinement through supercooling of the melt and therefore increasing the grain boundary surface area and thirdly, by trapping oxygen impurities within the semi-coherent molybdenum carbide. The hardening effects of the finely dispersed carbide network must be countered by utilizing a substrate temperature of 800 °C to prevent cold cracking. The herein presented alloying and processing strategies enable Mo-0.45 wt.% C to be PBF-LB/M-manufactured free of cracks.
| Speaker Country | Austria |
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| Would you like to publish your paper in the special issue of BHM "Berg- und Hüttenmännische Monatshefte" | No |