Abstract
Cast nickel aluminum bronze (NAB) alloy is widely used for large engineering components in marine applications due to its excellent mechanical properties and corrosion resistance. Casting porosity, as well as coarse microstructure, however, are accompanied by a decrease in mechanical properties of cast NAB components. Although heat treatment, friction stir processing, and fusion welding were implemented to eliminate porosity, improve mechanical properties, and refine the microstructure of as-cast metal, their applications are limited to either surface modification or component repair. Instead of traditional casting techniques, this study focuses on developing NAB components using recently expanded wire arc additive manufacturing (WAAM). Consumable welding wire is melted and deposited layer-by-layer on substrates producing near-net shaped NAB components. Additively-manufactured NAB components without post-processing are fully dense, and exhibit fine microstructure, as well as comparable mechanical properties, to as-cast NAB alloy. The effects of heat input from the welding process and post-weld-heat-treatment (PWHT) are shown to give uniform NAB alloys with superior mechanical properties revealing potential marine applications of the WAAM technique in NAB production.
Highlights
Cast nickel aluminum bronze (NAB) alloys are widely used for marine applications due to their excellent mechanical properties and corrosion resistance
Apart from mechanical properties, NAB alloys are characterized by their excellent corrosion behavior, partially because Ni and Fe extend the terminal α phase field and suppress the γ2 phase formation that occurs in binary Cu-Al alloys
This study focuses on the wire arc additive manufacturing (WAAM) of NAB components
Summary
Cast nickel aluminum bronze (NAB) alloys are widely used for marine applications due to their excellent mechanical properties and corrosion resistance. As summarized by Brezina [1], NAB is a copper-based quaternary alloy that typically contains 8–12 wt % aluminum, 3–6 wt % nickel and iron It has a two-phase microstructure, an equilibrium fcc α phase and a high-temperature bcc β phase. Several methods for improving the microstructure and mechanical properties of NAB e.g., heat treatment, friction stir processing (FSP), and fusion welding, are reported in the literature. Fuller et al [5] achieved microstructure refinement and homogenization, as well as closure of porosity of as-cast NAB materials through FSP This modification method is only available for near-surface layers rather than for through-thickness components due to the shallow pin depth of the FSP tools [7]. Corrosion behavior was intensively investigated and can be found elsewhere [15,16]
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