Abstract
In this paper we describe the creep behaviour of 9Cr-1Mo-0.2V steel under disc-bend loading, also known as the small-punch method. An improved power-law, stress-dependent, energy-barrier model was used to describe the creep behaviour of 9Cr-1Mo-0.2V steel because the characteristics of this steel cannot be accurately described using a simple, Arrhenius-type power law. A good correlation between the calculated values from the improved model and the experimental data was obtained for discs of different thickness, i.e., 0.50 mm, 0.47 mm and 0.44 mm. We found that the optimum disc thickness for our small-punch device was 0.50 mm. The stress-dependent, apparent activation energy of creep for a disc thickness of 0.50 mm decreased from ∼543 kJ mol^-1 to ∼535 kJ mol^-1 as the load increased from 350 N to 550 N, with the load exponent equal to 4.5. These values are very close to the results from conventional, uniaxial creep tests.

Key words
Small-punch, 9Cr-1Mo-0.2 V steel, creep equation, stress-dependent activation energy, Monkman-Grant relationship

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