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| A comparative research of porosity in stainless steel powders manufactured by
vacuum induction-melting gas atomization and plasma rotating electrode process |
| HU Jiaqi，WANG Changjun，WEI Lai，YANG Zhe，LIANG Jianxiong，DONG Han |
| Iron and Steel Research Institute, Beijing 100081, China |
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Abstract In this paper, a comparative research on the characteristics of porosity in stainless steel powders manufactured
by vacuum induction-melting gas atomization (VIGA) and plasma rotating electrode process (PREP) were
conducted via metallographic examination. The results show that the number of hollow powders increases with the
increment of particle size in both powders. Meanwhile, the morphology of porosities primarily exhibites a spherical
shape. The forming mechanisms of porosity in VIGAed and PREPed powders are quite different in essence. The atomization
is accompanied by the rapid cooling of droplets during VIGA process. The incomplete bag breakup during
secondary breakup stage causes gas preservation inside the liquid film. Considerable hollow powders form after
droplets solidification due to the gas preservation. While in the case of PREP with low pressure of gas (0.1
MPa), a minute amount of gas enters into the core of melted end face under the negative pressure generated from
high-speed rotation of the metal bar. The invaded gas would further move along with the liquid film. The gas-containing
liquid film forms droplets under the control of centrifugal force. Consequently, a small amount of hollow
powders with porosity are produced after solidification during PREP.
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Received: 09 April 2019
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2021, Vol. 31 
