Microstructure and mechanical properties of spray formed ultrahigh-carbon steels

Abstract

The microstructure and mechanical properties of the spray formed 1.25C–3.0Si–1.5Cr ultrahigh-carbon steel (UHCS) were described. The 1.25C–3.0Si–1.5Cr UHCS was processed by spray forming to break up carbide networks. The fine pearlites with average interlamellar spacing of 0.20 μm was observed in the as-sprayed microstructure. The ultimate tensile strength and the pearlite spacing can be related by the Hall–Petch equation. The as-sprayed 1.25C–3.0Si–1.5Cr UHCS consisting of fine lamellar pearlites has been shown to exhibit superplastic behavior at elevated temperature. The dramatic change of microstructure from fine lamellar pearlites to equiaxed grains stabilized by spheroidized particles during superplastic deformation has been observed. The estimation on the basis of thermodynamics shows that the content of chromium of 1.54 wt.% is needed to inhibit graphite formation in the 1.25C–3.0Si–1.5Cr UHCS.