Izvorni znanstveni članak
https://doi.org/https://doi.org/10.5599/jese.3245
Electroless cobalt coating of BNi-2 powders: process development and characterization
Tansu Göynük
; Department of Metallurgical and Materials Engineering, Middle East Technical University, 06800, Ankara, Türkiye
*
İshak Göynük
; ROKETSAN Inc., P.K. 30 Elmadağ 06780 Ankara, Türkiye
* Dopisni autor.
Sažetak
Electroless cobalt deposition and examination of how cobalt enrichment on the particle surface modifies the chemical composition and thermal behaviour of the commercial
BNi-2 brazing alloy powder was investigated in this study. A multi-step surface preparation sequence involving oxide removal, Sn-based sensitization, and Pd activation was employed prior to cobalt deposition in an alkaline CoSO₄-NaH₂PO₂ bath. A design of experiments approach was used to evaluate the influence of plating temperature, cobalt sulphate concentration, hypophosphite concentration, and coating time on cobalt uptake. ICP-OES analyses showed that cobalt incorporation increased from 1.1 to 7.0 wt.% across the selected parameter range. Differential scanning calorimetry revealed that coating levels up to 7 wt.% Co elevate the solidus temperature, while decreasing the liquidus temperature, resulting in a narrower melting interval. Thermodynamic simulations confirmed these trends, showing suppression of borides and enhanced γ/γ′ stability where γ denotes the Ni-rich face-cantered cubic matrix phase and γ′ represents the ordered Ni₃(Al,Ti)-type strengthening phase with increasing cobalt content. EDS mapping of coated powder showed continuous cobalt distribution at the particle perimeter. Overall, the results provided a quantitative basis for linking coating parameters to cobalt incorporation and corresponding modifications in melting behaviour.
Ključne riječi
Ni-based braze alloy; brazing powder modification; cobalt plating; plating experimental design; coated powder
Hrčak ID:
351685
URI
Datum izdavanja:
14.5.2026.
Posjeta: 0 *