Effect of Cobalt Additions on the Microstructure and Mechanical Properties of As-Cast Thin-Wall Ductile Iron

Effect of Cobalt in Thin Wall Ductile Iron and Solid Solution Strengthened Ferritic Ductile Iron

“…13 Interaction plot between cobalt and thickness on tensile strength[79].The addition of 4 wt.% Co resulted in a decrease of the yield strength as observed in the main effects plot(Figure 4.14). A drop in yield strength for all thicknesses with 4 wt.%Co is confirmed in the interaction plot(Figure 4.15).…”

“…1 (a) CAD model illustration with dimensions (mm)[79], and (b) a finished chemically bonded mold.The second mold contained three ASTM A536[80] ½ inch Y-blocks(Figure 3.2). Each sand mold weighs 34 pounds, and 11 molds were poured per heat for a total of 55 molds.…”

“…Interaction plot between cobalt and thickness in nodule count[79]. 4.1.2.1.2 Ferrite, Pearlite, and Carbide Analysis The 3 mm sections etched with 2% Nital are shown in Figure 4.4, with all etched micrographs for the other thicknesses provided in Appendix A. Carbides were found for the base ductile iron, 1 wt.% Co, and 2 wt.% Co heats, but the 3 wt.% and 4 wt.% Co heats had no carbides and an increase in ferrite percentage.…”

“…Ferrite, pearlite, and carbide percentages for all section thicknesses[79].4.1.2.2 ASTM ½ inch Y-blocks4.1.2.2.1 Graphite AnalysisThe unetched micrographs at 50x of the first and last Y-blocks poured show that adding cobalt results in an increase in nodule count and a decrease in the nodule size (Figure Unetchedmicrographs at 50x of the first and last ½ inch Y-blocks poured[81].For the first Y-blocks poured, there was not a substantial difference in nodularity among all the heats(Figure 4.7). A decrease in nodularity with time is observed when comparing the first and last Y-blocks poured likely due to Mg fade(Figure 4.7).…”

“…24 Effect of cobalt additions on the Brinell hardness of the rectangular plates. Error bars are 95% Std error of the mean[79].…”