Indentation creep analysis of T22 and T91 chromium based steels

Classical creep tests are very time-consuming, they usually take more than one year for steels, whereas creep analysis by instrumented indentation tests (IIT) only requires few hundred minutes. By IIT, creep is observed when the indenter continues to penetrate into the material at constant indentation load which leads to a horizontal plate in the load-depth curve. However, an indentation test cannot reasonably replace the conventional creep test. This is the reason why the objective of this work is to propose a methodology to classify the materials according to their creep sensitivity by means of the indentation test. Within this objective, the indentation testing conditions (dwell-time, maximum indentation load, loading rate and indenter shape) are optimized regarding the ability of the different models to adequately represent the time-indenter displacement variation. Applied to the study of T22 and T91 chromium based steels, the proposed methodology by indentation allows the identification of the creep behavior of these two materials. Furthermore, it is found an analogy with classical creep test through the stress exponent. (C) 2015 Elsevier B.V. All rights reserved.