Abstract:
This article reports on the comparative study of the hot deformation behaviour of virgin (steel A) and rejuvenated heat treatment creep-exhausted (steel B) P91 steels. Hot uniaxial compression tests were conducted on the two steels at the deformation temperature range of 900°C-1050°C and a strain rate range of 0.01-10s-1 to 0.6 strain using Gleeble® 3500 equipment. The results showed that the flow stress largely depends on the deformation conditions. The flow stress for the two steels increased with an increase in strain rate at a given deformation temperature and vice versa. The flow stress-strain curves exhibited a dynamic recovery as the softening mechanism. The material constants determined using Arrhenius constitutive equations were: stress exponent was: steel A (5.76) and steel B (6.67), and the apparent activation energy was: steel A (473.1 kJ mol-1) and steel B (564.5 kJmol-1). From these results, steel A exhibited better workability than steel B. Statistical parameters analyses showed that the flow stress for the two steels had a good correlation between the experimental and predicted data. Pearson’s correlation coefficient (R) was: steel A (0.97) and steel B (0.98). The Average Absolute Relative Error (AARE) values were: 7.62% (steel A) and 6.54% (steel B). The study shows that the Arrhenius equations can effectively describe the flow stress behaviour of P91 steel, and this method is applicable to the industrial metalworking process.
