Failure Mechanism Analysis of Radiant Tube of CrNiNRE Heat Resistant Steel for Carburizing Furnaces

By means of SEM analysis,EDS and X-ray diffraction,the failure mechanism and the microstructure of the radiant tube for carburizing furnace made of austenite heat-resisting cast steel CrNiNRE containing high Cr,Ni and RE in the long-term and high temperature carburizing environment were investigated and analyzed.The results indicate that the long-term high temperature unilateral carburizing makes the M_7C_3 carbide grow up perfectly,and promote the austenite region diminished and form crack around the carbide.The re-distribution of alloying elements results in chromium dilution in the austenitic matrix.The oxygen invasion in inside wall of the tube results in the interior porous and the oxidized cavity.These factors synthetically cause the tube failure finally by opening into one another.