WC particles distribution model in the cross-section of laser cladded NiCrBSi + WC coatings, for different wt% WC
Por:
Ortiz, A., García, A., Cadenas, M., Fernández, M.R., Cuetos, J.M.
Publicada:
1 ene 2017
Resumen:
This paper studies the non-homogenous distribution of non-melted tungsten carbides in NiCrBSi + WC coatings obtained by laser cladding. Ni base metal matrix coatings reinforced by spherical shape WC particles show a good wear performance in dry sliding contacts. However, during the cladding process, WC particles tend to fall down to the bottom of the melted coating, and as a consequence, the percentage of carbides increases near the interface with the C45E steel substrate, and decreases on the top of the coating. Distribution of carbides was studied in coatings made with different weight percentages of WC adjusted in the feeder (10, 20, 30, 40 and 50 wt% WCfeeder). The process parameters for different wt% WC were adjusted in order to obtain coatings with similar height (due to the different densities of base Ni alloy and WC, the powder feed rate had to be adjusted in the cladding process). An image treatment software was used to measure the volume percentage of WC particles along the entire depth of the coating. As a result, a WC distribution model is presented. All the coatings studied (10 to 50 wt% WCfeeder) show similar behaviour: The percentage of WC at the bottom of the coating is greater than the theoretical percentage of the coating (% adjusted at the feeder), and lower than the theoretical percentage at the top of the coating. Also, in this area, all specimens present around 40% of the theoretical percentage of carbides. This model of distribution of carbides allows to obtain an optimized manufacturing process in coatings made for wear performance. This is obtained by simultaneous control of the theoretical percentage of particles and the grinding depth of the coating. The same actual concentration of WC on the surface of the coating can be obtained with different combinations of wt% WCfeeder and grinding depth. © 2017 Elsevier B.V.
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