As cast high silicon ductile irons with optimised mechanical properties and remarkable fatigue properties

The present work shows a comparative study regarding the mechanical properties of 25 as cast ferritic ductile iron alloys, nine of them with silicon contents higher than 3.00% and carbon contents lower than 3.60%. In a first step, different carbon equivalent values have been used in order to analyse the effect of this parameter on the mechanical properties. After this comparative analysis, the composition ranges C=3.30-3.40 wt-% and Si=3.75-3.80 wt-% have been selected as the most proper ones to optimise the tensile and impact properties among the high silicon ductile iron alloys. Finally, a second study was carried out to compare the tensile and fatigue properties of the optimised high silicon alloy with the corresponding ones obtained from an EN GJS 400-18-LT grade alloy with low silicon content. Although the room temperature impact values obtained from the high silicon ductile iron are lower than 6 J cm(-2), the measured fatigue limit of this alloy (358 MPa) is clearly higher than the one obtained from the low silicon cast iron (170 MPa). A discussion about the benefits and advantages of the high silicon alloy is included.