EFFECT OF DECARBURIZATION ON NOTCH SENSITIVITY AND FATIGUE-CRACK-PROPAGATION RATES IN 12 MoV STAINLESS-STEEL SHEET

摘要

Tests were conducted in order to determine the effect of surface decarburization on the notch sensitivity and rate of fatigue crack prop-agation in 12 MoV stainless-steel sheet at room temperature. Three speel-men configurations were utilized in the course of the investigation:standard tensile specimen, 9-inch-wide specimens containing fatigue cracks or thread-cut notches of 0.005-inch radius, and 2-inch-wide specimens con¬taining fatigue cracks. The 12 MoV stainless-steel sheet in the normal condition was found to have an ultimate tensile strength of 251 ksi and to be extremely notch sensitive. The material in the decarburized condition was found to have an ultimate tensile strength of 210 ksi and to be con¬siderably stronger than the normal material in the presence of fatigue cracks. Decarburization did not appear to have any significant influence on the rate of fatigue crack propagation in the 2-inch-wide specimens at the stress levels considered. In addition to the tests, two methods for predicting residual static strength and their application to the material are discussed.