Sintering solution on the International Space Station

Image: MSL low-gradient furnace with flying furnace handle installed. see more 

An experiment on the International Space Station is testing a centuries-old material bonding process, which may pave the way for more research on such materials in the orbital laboratory. Sintering is the process of heating different materials to compress their particles together.

"In space, the rules of sintering have changed," said Rand German, the lead researcher of the survey named NASA Sample Cartridge Assembly-Gravitational Effects on Distortion in Sintering (MSL SCA-GEDS-German). "The first time someone tried to sinter in a different gravitational environment or even a microgravity environment outside of the earth, they might be surprised. It's just that there have not been enough experiments to tell us what the result will be. In the end we have to experience, give it a try, See what happens."

If the difference between sintering on earth and space sintering can be better understood through continuous experiments, then this technology is expected to become a flying manufacturing solution or a reliable way to piece together on-site resources. Mars or lunar missions can use this sintered new knowledge to piece together habitats in the lunar or Martian soil, called regolith. The weathered layer includes mixed sediments such as loose rocks, dust, and soil.

The sintering process is used for a variety of everyday products, which require metal bonding from the metal parts of a watch to a set of brackets or hinges on glasses. A familiar example of this process is the bonding that occurs when ceramics are fired in a kiln.

The experiment relies on sintering to study the behavior of the new alloy under microgravity.

"After the 1940s, sintering as a manufacturing process really started to take off," German said. "Once the automotive industry adopts it, there will be amazing growth in the field. Now we want to take sintering into space."

The components used for the investigation were transported to the space station on SpaceX CRS-14 and launched in the Materials Science Laboratory Low Gradient Furnace (MSL-LGF) in the Materials Science Research Rack One (MSRR-1).

The survey uses a process called liquid phase sintering to test the degree of sintering deformation caused by microgravity. Slightly different from traditional sintering, liquid-phase sintering introduces materials with a lower melting point into the mixture to combine particles that are not easily sintered. The molten additives speed up and improve the bonding process. The result may allow scientists to adjust future calculations to create more successful bonds in microgravity.

"Sintering occurs at the atomic level," German said. "The increase in temperature will cause these atoms to move, and the liquid phase we studied helps this atomic transport. On Earth, we have a very stable structure in which the particles are pushed together by gravity, but in our previous experiments It was found that without the compression of gravity, the sintered parts would undergo huge deformation."

Initially, the German team's scientists wanted to sinter tungsten, nickel and ferroalloys, but the team had to be creative to adapt to a temperature of 1210 degrees Celsius-the highest temperature allowed by the station's low gradient furnace. Their solution? Create a new alloy. Although based on previous research on the melting point and sintering applications of manganese, the substance created for this research is a new combination of tungsten, nickel, copper and manganese.

The alloy can even be used for low-temperature sintering on the earth. This combination process has revolutionized and expanded the options of the additive manufacturing industry. Although the influence of the earth's gravity is well known and defined as sintering on the ground, the results of the investigation can still improve the process and new insights into deformation. Similarly, the new alloy developed by the German team can be used in various industrial applications.

The survey was sponsored by the Space Life and Physical Science Research and Applications Division (SLPSRA) at NASA Headquarters in Washington.

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Rachel Barry rachel.barry@nasa.gov Office: 281-244-7449

Copyright © 2021 American Association for the Advancement of Science (AAAS)

Copyright © 2021 American Association for the Advancement of Science (AAAS)