Abstract
Cu-doped martensitic steels (Fe–(13, 16)Cr–3W–2Cu–1C) (mass%) with multiple carbide precipitates were prepared at different quenching temperatures, and their corrosion behaviours were examined by measuring the weight loss during immersion in a 0.5 M H2SO4 solution. Lower weight losses and corrosion rates were obtained for the alloy samples prepared at higher quenching temperatures. Surface Cu enrichment was observed for all specimens with a large fraction of dissolved Cr species. Moreover, quenching from higher temperatures not only reduced the amount of M23C6 carbide but also decreased the local electrochemical potential difference between the carbide phase and the martensitic matrix via enhanced surface Cu accumulation, thus increasing corrosion resistance by suppressing microgalvanic corrosion between the constituent phases. The corrosion behaviour of the studied steels was remarkably different from those of the Cu-doped stainless and low-alloy steels with passive oxide surface films, suggesting the strong effect of multiple carbide precipitates on their corrosion behaviour.
Highlights
High-speed steels (HSS) with high carbon content (0.65–1.60 mass% according to the ASTM A600 standard1) and alloying elements such as Cr, W, Mo, V, and Co2 are widely used for manufacturing cutting tools because of their high hardness and wear resistance
Electron backscatter diffraction (EBSD) measurements (Supplementary Fig. 1) captured the lath martensitic matrix in all the specimens, whereas the ferrite grains in the as-received bars remained intact during heat treatment at 800 °C
Higher carbide peak intensities were observed for the samples heat treated at 800 °C, whereas the retained γ-phase is detected were observed at each quenching temperature
Summary
High-speed steels (HSS) with high carbon content (0.65–1.60 mass% according to the ASTM A600 standard1) and alloying elements such as Cr, W, Mo, V, and Co2 are widely used for manufacturing cutting tools (e.g., taps and dies) because of their high hardness and wear resistance. These steels comprise martensitic matrices containing fine carbide particles with the formulae MC, M2C, M6C, and M7C3, depending on the chemical composition and steel processing method[3,4,5,6,7]. The corrosion resistance of HSS is often insufficient for practical applications because of their low Cr content (
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