High-cycle fatigue properties prediction and damage mechanisms of RuT400 compacted graphite iron at different temperatures

Abstract

As a new type of cylinder head material, the mechanical properties of RuT400 compacted graphite iron (CGI) are particular critical for its industrial application. In this study, the tensile and high-cycle fatigue (HCF) tests of RuT400 were performed at 25, 300, 400 and 500 °C, respectively. Meanwhile, the original microstructure, hardness (HV) and damage features of typical fatigue fractured specimens at each temperature were investigated. It is found that, with the temperature increasing, the tensile and yield strengths decrease slightly first and then rapidly, while, the fatigue strength increases first and then drastically reduces. Several different analyses indicate that the variation of fatigue strength due to the matrix microstructure changing. Besides, a new prediction method of fatigue properties was proposed, it can reasonably predict the HCF properties for CGI at any temperatures. These results will enrich the understanding on the strength improvement of the CGI.