Small specimen test techniques for estimating the tensile property degradation of modqa 9Cr-1Mo steel on thermal aging

Abstract

The degradation in mechanical properties of modified (mod) 9Cr-1Mo steel on thermal aging at 923 K has been studied using the small specimen test techniques-shear-punch and ball-indentation tests. Small volumes of material required for these test techniques make them unique tools for the assessment of service related degradation and failure analysis of structural components. A variety of heat treated microstructural conditions of mod 9Cr-1Mo steel is generated on which both conventional tensile test and shear-punch/ball-indentation tests are carried out. The relationship between conventional tensile properties and small specimen test results is established from these standardization experiments. Small specimens of Mod 9Cr-1Mo steel in the thermally aged conditions are tested using both shear punch and ball-indentation techniques and the tensile property changes are determined. Both these tests identically reflect and quantify the changes in the tensile properties with aging time which correlates well with the microstructural changes observed using optical and electron microscopic studies.