Thermal Fatigue Testing of SiMoCr Compacted Graphite Cast Iron for HPDC Tooling Application

SiMoCr CGI (compacted graphite iron) has the potential to be a cost-effective replacement for some hot working tool steel parts like shot sleeve in HPDC (High-Pressure Die Casting) applications. Thermal fatigue testing of SiMoCr CGI cast alloy was performed on Gleeble 1500D machine. Cracks were evaluated on non-nitrided and nitrided samples at test temperatures of 400 and 600 °C, after 1000, 2000 and 4000 thermal cycles. Samples were heated to prescribed test temperature and afterward cooled in computer-guided cycles. After the test, all the samples were axially and radially sectioned and cracks on cross sections were evaluated. Length of all cracks which occurred was measured and statistically evaluated, i.e., the average length of cracks and distribution of crack lengths were determined. At nitrided samples, higher values for average crack lengths were obtained while density of cracks was lower in comparison with non-nitrided samples.