SEM SE and BSE images of the cross sections of both coatings are presented in Fig.1. Both coatings have densely packed structures with no signs of cracking, with good adhesion to the substrate, as can be seen due to a total lack of any crack or delamination along the interface. The NiSF_HF and NiSF_LF coatings had a measured thickness of(518±11)um and(576±8) um. The splats of the Ni alloy and WC-Co particles can be seen throughout the microstructure, with many Ni alloy splats still retaining their spherical shape. The diameter of 10 spherical Ni alloy splats seen from cross sectional BSE images of the coatings were measured, with the average diameter in the NiSF _HF and NiSF_LF coatings found to equal(41±11) um and (37±7) um respectively; however, this may differ depending on how the sample was prepared.
Fig.1.(a,b) SEM secondary electron images of the NiSF_HF and NiSF_LF coatings.(c,d) BSE images of the coating microstructures. Intersplat phases are marked on the images with a red arrow.(For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
The Cr rich areas that can be observed on the cross section of the Ni alloy particles in Fig.2 can also be observed within the coating microstructure within some Ni alloy splats. Thin string like phases with a bright contrast, marked on Fig.1 with red arrows, can be seen positioned between splats of Ni alloy throughout the microstructure of bothcoatings. An EDX line scan across one such site was carried out with the results displayed in Fig.3. The areas scanned in the darker contrast area were found to contain large element weight percentages of Ni(>60%)with little measured W and Co(<15%). The scanned points in the brighter contrast region were still seen to contain measureable amounts of Ni, with a spot roughly in the centre of the feature measured to contain an elemental weight percentage of approximately 15% Ni. Thismay indicate that a form of mixing between the two separate powders has taken place; however, whether or not this is due to the EDX generation region being larger than the measured phase is the reason for the detection of Ni cannot be confirmed.
Fig.2.SEM secondary electron image of the composite feedstock powder.EDX point scans were carried out on the marked areas.
Fig.3.EDX line scan across the intersplat phase marked in Fig.1.
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