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Scientists successfully 3D printed stainless steel strength 3 times

3D printing technology is already popular all over the world, but at present the best combination of this technology is plastic and foam steel materials, but these materials are not strong enough to meet the core material application requirements. Now researchers have developed a tough, flexible stainless steel technology for 3D printing that may lead to faster and cheaper methods of manufacturing everything from rocket motors to nuclear reactor and well equipment components product.

Stainless steel was invented 150 years ago and is still popular today. It is made by melting a traditional steel structure - a mixture of iron and carbon (sometimes other metals such as nickel) itself, plus chromium and molybdenum to prevent rust and corrosion. In the stainless steel manufacturing process, a series of complicated steps of cooling, reheating and rolling make the microstructure of the material closely arranged, that is, the alloy particles form a cell-like structure with the particles. When the metal is bent or pressed, the atomic layers in the particles slide against each other, sometimes forming crystalline defects, resulting in the generation of cracks. But solid grain boundaries prevent these defects, make the material hard, and still flexible enough to form a desired shape.

For a long time, 3D printing researchers have been trying to copy this structure. Their plan started with a layer of metal alloy particles smeared on a flat surface.

In this study, a computer-controlled, high-performance laser beam scans back and forth across the surface. The particles hit by the laser melt and fuse together. This surface was then moved downwards, followed by the addition of another layer of powder, after which the laser heating process was repeated again, adhering the newly melted material to the underlying layer. By repeating this layer-by-layer addition, engineers can make complex structures, such as rocket motors.

However, the problem persists - at the microscopic level, 3D-printed stainless steels are generally highly porous, which also makes them brittle and prone to breakage.

"The performance of these steels is very poor." Yinmin "Morris" Wang says he is a material scientist at Lawrence Livermore National Laboratory in California. Several years ago, Wang and his colleagues proposed a method of using laser and a rapid cooling technique to fuse metal alloy particles in a dense and compact structure.

Today, they extend this work by designing a computer-controlled program that not only makes dense stainless steel layers, but also controls the structure of these materials more strictly-from the nanoscale to the micrometer. This allows 3D printers to build tiny cell-wall structures on every scale, preventing cracking and other common problems.

Tests have shown that under certain conditions, the final 3D printed stainless steel is three times harder and more ductile than stainless steel produced by conventional processes.

The research was reported in Nature - Materials on October 30.
"What they did was really exciting," said Rahul Panat, a mechanical engineer at Carnegie Mellon University in Pittsburgh, Pa. In addition, Panat pointed out that Wang and his colleagues did the job using a commercially available 3D printer and laser device. This makes it very likely that other research groups will quickly follow suit, creating a wide range of high-strength stainless steel components - from the tank of the aircraft to the pressure tube at the nuclear power plant. At the same time, it may also increase people's enthusiasm for 3D printing.

3D printing
is a rapid prototyping technology that builds objects by layer-by-layer printing based on digital model files using bondable materials such as powdered metal or plastic. 3D printing is usually done using a digital technology material printer. It is often used in mold making, industrial design and other fields to make models. It is being used for the direct manufacture of some products. There are already parts that are printed using this technology appear. The technology has applications in areas such as jewelry, footwear, industrial design, construction, engineering and construction, automotive, aerospace, dentistry and healthcare, education, GIS, civil engineering, firearms and many more.