Microstructure, mechanical and fatigue properties of SiMo- and SiCu- nodular cast irons

Fatigue has been a predominant fracture mode of load-bearing machine members. Therefore, through the years its prevention has become a fundamental design criterion. The objective of this study was to compare the microstructure, mechanical and fatigue properties of two types of the nodular cast irons ferrite-pearlitic nodular cast iron alloyed by Si and Mo and pearlite-ferritic nodular cast iron alloyed by Si and Cu. Microstructure of the specimens was evaluated according to STN EN ISO 945 and by automatic image analysis. The image analysis system NIS Elements, interfaced with the light microscope, was used for evaluation of the shape factor, count of graphitic nodules and content of ferrite. Fatigue tests were realised at sinusoidal cyclic push-pull loading (stress ratio R = 1) at ambient temperature (T = 20 5 C). They were carried out in the high cycle fatigue region (from 105 to 107 cycles) at frequency f 75 Hz using the fatigue experimental machine Zwick/Roell Amsler 150HFP 5100. The relationship between the amplitude of stress ua and number of cycles to failure Nf, as well as the fatigue strength, were determined. (C) 2018 The Authors. Published by Elsevier B.V.