VHCF strength decrement in large H13 steel specimens subjected to ESR process

Failures at very high number of cycles (Very-High-Cycle Fatigue, VHCF) generally originate from inclusions or defects present within the material. VHCF response of materials is therefore strongly affected by the defect population and, in particular, by the characteristic defect size, which statistically increases with the material volume. According to this well-known dependency, Size Effects were found to significantly affect the VHCF strength of high-strength steels. The paper aims at assessing the influence of Size Effects on the VHCF response of a high performance AISI H13 steel subjected to Electro Slag Remelting (ESR) refinement process. Ultrasonic VHCF tests were carried on specimens characterized by different loaded volumes (hourglass and Gaussian specimens). Experimental results showed that Size Effects strongly influences the VHCF response of the investigated high performance steel, even if it is characterized by a high degree of purity and by a population of inclusions with limited size.