High silicon grades of ductile cast iron are known to be highly advantageous in regard to technically relevant properties and economic efficiency. In particular, the outstanding mechanical properties lead to an increasing demand since 2011, the year of incorporation to the EN 1563 standard. However, low impact resistance and spontaneous failure are concerns that limit the application, especially at lower temperatures. Silicon serves as a solid solution strengthener. By the addition of cobalt, aluminum and nickel as additional solid solution strengthener, an improvement in mechanical properties compared to only silicon could be obtained. Previous studies showed that the addition of 1.5 wt.% Ni to an EN-GJS-500-14 grade with 3.8 wt.% Si resulted in a tensile strength of 650 MPa at 15 % elongation. In the present study, silicon was substituted stepwise by nickel and aluminum, simultaneously aiming at the retention of the mechanical properties of the EN-GJS-500-14 grade. By decreasing the silicon content to 3.3 wt.% Si at 1.1 wt.% Ni and 0.2 wt.% Al, EN-500-14 was obtained. Even though, the presence of pearlite in the matrix was observed, this substitution of silicon led to an increase in Charpy-V-notch toughness by 4 Joule at room temperature. For further alloy design of high silicon ductile cast iron for simultaneously substituting silicon and improving the mechanical properties and notch toughness, the restrictions for pearlite formation must be complied.
Notch strength of high silicon ductile cast iron and wide applicability to structural design
