Sintering of pure B4C and Ni2B nanolayer‐coated B4C was studied from 1300° to 1600°C, with the holding time at the peak temperatures being 2 or 10 h. Compacts were made by uniaxial die compaction and combustion‐driven compaction. Pure B4C sample shows less sintering at all conditions. Ni2B‐coated B4C sample shows more extensive densification, neck formation, and grain shape accommodation. The combustion driven compaction process accelerates sintering by offering higher green density to start with. The Ni2B species on the B4C particle surfaces melts into a nickel–boron‐containing liquid phase during heating, remains as liquid during sintering, and then transforms into Ni4B3 and NiB during cooling. High‐resolution composition analysis shows that there is no nickel diffusion into bulk B4C during the sintering process. However, there is boron diffusion into the Ni2B coating layer. Carbon diffusion cannot be directly measured but is believed to be a simultaneous process as boron diffusion. A multievent sintering process has been proposed to explain the observations.
Lasers are useful for performing operations such as joining, machining, built-up freeform fabrication, shock processing, and surface treatments. These attributes are attractive for the supportability of longer-term missions in space due to the multi-functionality of a single tool and the variety of materials that can be processed. However, current laser technology also has drawbacks for space-based applications, specifically size, power efficiency, lack of robustness, and problems processing highly reflective materials. A review of recent laser developments will be used to show how these issues may be reduced and indicate where further improvement is necessary to realize a laser-based materials processing capability in space. The broad utility of laser beams in synthesizing various classes of engineering materials will be illustrated using state-of-the art processing maps for select lightweight alloys typically found on spacecraft. With the advent of recent breakthroughs in diode-pumped solid-state lasers and fiber optic technologies, the potential to perform multiple processing techniques is increasing significantly. Lasers with suitable wavelengths and beam properties have tremendous potential for supporting future space missions to the moon, Mars and beyond.
Conventional manufacturing from wrought bar stock typically involves extensive machining, creates significant material waste (scrap metal), and requires numerous steps to obtain the final part geometry. As a more efficient alternative, powder metallurgical (PM) processes are now available to cost effectively fabricate both simple and complex shapes with minimal material waste. Combustion driven higher pressure powder compaction (CDC) for near-net or net shape manufacturing was recently developed. It offers a unique way of forming near-net or net shape high-density powder metal components both cost effectively and at relatively higher compaction pressures than other PM processes.
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