Formation of Flake Particles during Plasma Rotating Electrode Process of Ti6Al4V
PREP(Plasma rotating electrode process)is one of the most used methods to produce high quality spherical metal powders with low impurity.The main atomization mechanism of PREP is centrifugal atomization,which supports inertia force to resist surface tension of the molten liquid metal.Thus,compared with gas atomization mechanism,the centrifugal atomization uses less gas flow kinetic energy,which makes the contact possibility of gas to liquid system lower than gas atomization and forms fewer gas holes or porosity.However,the heat source of PREP is a kind of high speed plasma gas flow with super high temperature and thermal energy,which means that the plasma gas flow will also affect the powder forming process like gas atomization.For titanium alloys PREP,there is always existing 0.3-0.7%flakes particles in the received powders.This research has found that some irregular particles with flake shapes in PREP are formed by the reason of high speed plasma gas flow.The influence degree of different process parameters is tested by orthogonal experiment in this work.The results show that the width between the plasma nozzle and the electrode is the main heat parameter to influence the flake particles fraction.The width should be set to a suitable position.The temperature and gas flow speed of the plasma gas would fade when width increasing.Thus,too larger width makes the temperature too low and the spheroidization process is not complete.Smaller width also makes too much flake particles for the reason that the gas flow is too strong.For low-density alloys like titanium alloys,especially Ti6Al4V,the low density of molten pool could not get enough inertial force to resist the power of gas flow,being easier to make wave-shaped flakes during PREP.The solution for this phenomenon in this work is to increase the over-heated degree of the liquid pool and reduce the flow gas power.The results show that the fraction of the flakes powders can be decreased after promotion.
Spherical powder Ti6Al4V PREP Atomization model Irregular particle
Liu Yang Yan Fei Han Zhiyu Wang Qingxiang Liang Shujin
Sino-Euro Materials Technologies of Xian Co.,Ltd.,Xian 710018,China
国际会议
北京
英文
58-62
2018-09-16（万方平台首次上网日期，不代表论文的发表时间）