Application of creep small punch testing in assessment of creep lifetime

Abstract

In this contribution, the problem is investigated, whether the dependence of the time to rupture on the acting force in small punch tests can be analyzed in the same way as the dependence of time to rupture on the applied stress in conventional tensile creep tests. Two comparable sets of constant-force small punch tests and relevant conventional creep tests on P91 steel were performed at temperatures from 823 to 873 K. The experimental results were analyzed using various parametric approaches (Larsson–Miller, Fisher–Dorn, etc.) very well-known from conventional creep testing. It is shown that the methods based on time–temperature parameter can be used also for a description of small punch test data. The differences among various studied methods are negligible; the best description can be achieved with the Sud–Aviation parameter. The extrapolated data can be used for determination of empirical relationships between stress and minimum creep rate in the creep tests and force and minimum deflection rate in the small punch test.