Effect of carbon addition on microstructure and mechanical properties of as-cast nickel-based heavy density matrix alloy reinforced by high tungsten content

Abstract

In present work, a novel carbon-doped interstitial strengthening nickel-based heavy density matrix alloy reinforced by high tungsten content (Ni-W-Co) was prepared by conventional casting technology using a laboratory vacuum induction melting (VIM) furnace. The effects of carbon addition on as-cast microstructure and phase constituents were characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). And the tensile properties and microhardness were tested as well. Results demonstrated that the present heavy density alloy has a single-phase FCC structure and exhibits typical dendrite characteristics. The carbon content (0–0.021 wt%) presents little influence on as-cast microstructure and phase constituents, but significantly improves the mechanical properties. Both tensile strength and ductility of the matrix alloy were increased synchronously with the addition of interstitial carbon atoms on account of the interstitial strengthening. The tensile fracture morphology revealed the transition from complete ductile dominated features to a mixed fracture mode consisting of quasi cleavage and ductile fractures. Minor carbon addition can trigger an obvious increase for lattice parameters and thus contribute to the strength improvement, and the increase in lattice friction stress enhanced the work-hardening rate and postponed the necking of C-addition alloy compared with C-free alloy.