Comparative study on hot deformation behaviour of P91, RAFM-CLAM and Low C RAFM-CLAM steels by processing maps

摘要

The comparative study of high temperature deformation behaviour of P91, RAFM-CLAM and Low C RAFM-CLAM steels was done from compression deformation data in the temperature range of 850-1100 degrees C and the strain rate range of 10(-3)-10 s(-1). The processing maps in terms of strain rate sensitivity (m), % efficiency of power dissipation (eta) and the instability criterion (xi((epsilon) over dot)) were constructed in the temperature-strain rate space. The stable domains for hot processing with higher m and % efficiency values were identified. For P91, the stable domain was observed in between 970 degrees C-1100 degrees C at 0.01-1 s(-1) strain rate with maximum m value of 0.223 and 36% efficiency. For RAFM-CLAM steel, the stable domain was observed in between 1000 degrees C-1050 degrees C at 0.3-5 s(-1) strain rate with maximum m value of 0.189 and 30% efficiency. For Low C RAFM-CLAM steel, the stable domain was observed in between 900 degrees C-1000 degrees C at 0.01-0.1 s(-1) strain rate with maximum m value of 0.175 and 30% efficiency. The unsafe conditions for industrial hot working of the steels were determined from the negative values of xi((epsilon) over dot). The detailed kinetic analysis including activation energy and activation volume was carried out. The rate controlling mechanisms based on activation energy and activation volume values were concluded to be movement of screw dislocations and thermal activation breaking of attractive junctions.