Microstructural and Mechanical Assessment of Camshafts Produced by Ductile Cast Iron Low Alloyed with Vanadium

Abstract

In the present study, ductile iron camshafts low alloyed with 0.2 and 0.3 wt % vanadium were produced to study the microstructural and mechanical evaluation of lobes and camshaft. For this purpose, camshafts were produced in one of the largest manufacturers of the ductile iron camshaft in México by the phenolic urethane no-bake sand mold casting method. The microstructure of the lobes was studied in three zones located at the top, middle, and bottom of the lobes by optical microscopy, and mechanical tests were performed on lobes and camshafts. A homogeneous distribution of spheroidal graphite with high nodularity for both castings was obtained from the regions of the lobes analyzed. The high cooling rate on the lobe surfaces enabled us to obtain a high nodule count of a smaller size instead of the middle region where big nodules with a low nodule count are presented. An inverse chill behavior was found in the middle region of the lobes where there is an increase in the concentration of carbide-forming elements, leading to the highest micro-hardness values in this region. The tensile properties were increased when the vanadium contents were increased; however, the toughness and ductility of the as-cast alloys were decreased as a result of the increase of the volume fraction of carbide particles.