Abstract
Cold metal transfer (CMT) technology based on wire-arc manufacturing has attracted wide attention because of its advantages of high manufacturing efficiency, low heat input (HI) and near-net-shape. In this study, a CMT-Hastelloy C-276 superalloy surface modification coating by optimizing HI is used to solve the problem of premature failure of key over-flow components of stainless steel in marine engineering. When the HI is increased from 269 J/mm to 358 J/mm, the serious cavitation erosion (CE) damage caused by pore defects and excessive residual tensile stress due to excessive low HI of Hastelloy C-276 coating can be avoid, which is attributed to the effective Orowan strengthening and high proportion of low angle grain bounds (LAGBs: 70.2%). In addition, high contents of Cr, Mo and W elements can promote it's passivation film to maintain excellent self-healing ability during CE to provide continuous and stable protection effect (Rct = 75.68 kΩ·cm2) in the 3.5 wt% NaCl artificial seawater. Therefore, even after 10 h-CE, it still maintains the highest corrosion resistance from both of the thermodynamic (Ecorr = −193.5 ± 3.6 mV) and kinetic perspective (Icorr = 69.3 ± 3.1 μA·cm−2) and has the lowest mean depth erosion rates (MDER, 0.94 ± 0.07 μm/h). However, further increase of HI will cause coarsing of grains (89.6 ± 2.7 μm → 342.8 ± 9.7 μm), excessive precipitation of brittle Mo-rich p phase and excessive dilution of elements from the substrate, resulting in changes in the wear mechanism and deterioration of strength and corrosion resistance. Moreover, the potential of zero charge (PZC) measurements and Mott-Schottky (M-S) test confirmed the decreasing trend of the repulsive ability to Cl ions (ΔE = 0.58 V) and the increased ion doping concentration (ND = 5.94 ± 0.02 × 1022 cm−3) of the weakened n-type passivation films. The optimal combination of wear resistance, corrosion resistance and CE resistance of Hastelloy C-276 coating is obtained by regulating HI, which can lay a theoretical foundation for the related production and application of marine engineering.
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