Erosion-corrosion assessment of tungsten carbide-based plasma-tranferred arc-welded overlays

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Journal titleCorrosion
AbstractTwo commercially available tungsten carbide-based, Ni alloy binder plasma-transferred arc-welded (PTAW) overlays, which had both previously exhibited excellent resistance to slurry erosion (in substantially non-corrosive conditions) and abrasion, were assessed in a more corrosive slurry erosion environment. One overlay consisted of a 50 vol% mixture of crushed eutectic (WC/W2C), spherical eutectic, and tungsten monocarbide (WC) particles in a NiBSi matrix, while the other contained 50 vol% WC in a NiCrBSi matrix. Initial microstructural examination of the mixed carbide/NiBSi overlay confirmed that substantial dissolution/degradation of the spherical eutectic and crushed eutectic carbides had occurred as a consequence of interaction with its matrix alloy constituent at the high temperatures encountered during arc deposition. Conversely, the WC-based overlay exhibited very limited carbide dissolution or degradation. The total erosion-corrosion (E-C) rate, as well as its separate components, namely, erosion, corrosion, and synergy, was established using a novel slurry pot erosion-corrosion (SPEC) tester. The E-C rate for the WC/NiCrBSi overlay was approximately four times less than the E-C rate for the mixed carbide/NiBSi overlay, which performed comparatively poorly. The mixed carbide/NiBSi overlay displayed a very large synergistic value, which accounted for 90% of the total erosion-corrosion rate, with the WC/NiCrBSi showing a synergy level accounting for 50% of the total E-C rate. To establish and compare the damage mechanisms affecting both overlays, a novel technique was implemented where specific regions were examined using scanning electron microscopy (SEM) before and after SPEC testing. This procedure was applied to identify any preferential attack that was occurring and to elucidate the reasons for the significantly different E-C performance of the two products. The main reasons for the inferior performance of the mixed carbide/NiBSi overlay were found to be caused by the attack of the non-Cr bearing matrix and preferential removal of the W/Ni-rich boundary layer and eta-carbides, formed around the eutectic carbides during deposition.
Publication date
AffiliationNRC Institute for Fuel Cell Innovation; National Research Council Canada
Peer reviewedYes
NPARC number21269111
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Record identifier3b2a59a7-3140-435d-98f9-bbeb31629b26
Record created2013-12-05
Record modified2016-05-09
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