The effect of initial hot plastic deformation on creep behaviour of 12 Cr steel specimens in small punch tests

The results of small punch creep tests carried out on flat and on sombrero- shaped disk test specimens made of high-alloy 12 Cr steel have shown that t he time to rupture of the flat disk test specimens, which had been subject to rapid and large initial plastic deformation, was one order of magnitude shorter than that of the sombrero-shaped disk specimens whose contours had been shaped before the test to fit the shape of the punch. In the case of t he flat disk test specimens, the strain energy density was increased by the initial hot plastic deformation, this probably accelerated the dynamic rec overy and consequently reduced the time to rupture. However, the measured a ctivation energy and the power to which the load is raised are practically the same at small punch creep tests with flat disk test specimens as well a s at conventional constant load creep tests.