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How Shielding Gases such as Argon and Nitrogen Affect 3D Printing Stainless Stee

2019-05-05 15:52 admin

 A group of researchers studied the effects of argon or nitrogen as protective gases on the final mechanical properties of 17-4 PH stainless steel with additives.

"By investigating various process parameters, scanning strategies and building orientation effects, many efforts have been made to optimize and improve the mechanical properties of AM components," the researchers said.“The introduction of shielding gas is another important parameter that not only affects the thermophysical properties of the manufactured part, but also the mechanical properties of the manufactured part. The shielding gas is responsible for removing the reactive gases around the bath to prevent adverse effects from the reaction with the atmosphere. Like oxygenSuch gases must take into account various factors, such as the base material and chemical metallurgical reaction of the gas and the molten pool, when selecting a suitable shielding gas."

The effects of various protective gases such as nitrogen, argon and helium on the behavior of different materials such as carbon steel, stainless steel and aluminum alloy were investigated. The researchers' focus is "to simulate the thermal response of 17-4 PH SS by simulating a single orbit under typical L-PBF conditions, while considering the convective heat transfer of different shielding gases." Numerical studies were conducted to obtain the temperature, temperature gradient and cooling rate of the parts fabricated under argon and nitrogen shielding gas during the laser powder bed melting process. Microhardness testing and tensile testing were performed to determine the mechanical properties of the 3D printed components under different shielding gases. Concluded as follow:
1. The nitrogen atmosphere introduces a slightly lower temperature and temperature gradient along the track while the cooling rate is higher than the argon atmosphere. The researchers attributed this to the higher thermal conductivity of nitrogen.
2. When nitrogen is used as a shielding gas, more energy should be dissipated from the orbit to the environment. This is due to the higher cooling rate provided when using nitrogen.
3. The hardness of the sample fabricated under a nitrogen shielding gas is slightly higher than the hardness of the sample manufactured under argon. This is due to the finer microstructure obtained due to the higher cooling rate provided under a nitrogen atmosphere.
4. The hardness of the HT-Ar / Ar sample is higher than that of the HT-Ar / N2 sample. This is because the austenitic matrix produced under the argon atmosphere has higher precipitation hardening ability than the martensite microstructure. .
The change in tensile behavior was minimal under all test conditions. However, the 3D printed samples under nitrogen atmosphere have slightly higher strength and ductility.


China 3D Printing Network Comments: This research can provide valuable insights to better avoid the addition of defects in manufacturing parts, such as porosity and lack of fusion. In particular, the manufacture of metal additives is a very precise science involving a large amount of chemical knowledge and mathematical calculations to create the best conditions for 3D printing. According to researchers, manufacturers may be able to change the conditions of 3D printed parts to get better overall components.