Fe-Cr Melt Nitrogenation WhenExposedto Nitrogen Plasma

Abstract

The nitrogen absorption/desorption for pure iron and Fe-C alloys have been investigated in detail in levitated melts. However, Iimited study seemsto be madewhile molten Fe-Cr alloy is exposedto nitrogen plasma. Nitrogen plasma offers an attractive meansto nitrogenise Fe-Cr alloys in view of rapid absorption to higher nitrogen content. Several workers have reported that su]phur in the melt renders higher nitrogen. Industrially melt with higher nittogen with sulphur maynot be attractive. The experimental condition of present study solves this problem. Melts were madeto observe the effect of arc current, plasma gas composition, surface active elements (SAE) in melt on melt nitrogen content, It wasnoted that the nitrogen was first absorbed upto certain maximumlimit [N~.*] followed by its desorption on continued plasma exposure maybe dueto nitrogen bubble formation. Themaximumnitrogen level in melts could be enhanced whenrate of absorption in plasma arc zone wasmuchhigher with low desorption occurring in non-plasma arc zone of the melt. The use of higher melt temperature and low SAEin melt rendered higher absorption rate. The slower desorption rate could be obtained by maintaining lower SAEand temperature in melts. The nitrogen absorption in plasma arc zone followed first order reaction rate, however, desorption was probably dependedon bubble formation frequency.