Influence of Fe–Ni–Co binder composition on nitridation of cemented carbides

Nitridation of cemented carbides leads to the formation of wear resistant Ti(C,N)-enriched outer-surfaces (fcc-rich outer-surfaces). In this work the influence of the binder phase composition on the kinetics of formation of fcc-rich outer-surfaces was investigated. Sintered cemented carbides were nitrided at 1200 °C in a 5 bar N2 atm for 2 and 4 h. The thickness of the nitrided fcc-rich outer-surfaces increases with the addition of Fe to the Co and Ni binders. Correlations between nitrogen diffusion coefficients and nitrogen solubility levels in Fe–Ni–Co systems are investigated to understand the mechanisms governing the formation of graded layers on nitrided cemented carbides with Fe–Ni–Co binders.

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► Effect of Fe binder addition on nitridation of Co/Ni cemented carbides.
► Nitrided zone formation obeys a parabolic law (diffusion-controlled process).
► Thickness of nitrided zone larger for cemented carbides with Fe-based binders.
► Kinetics of nitrided zone formation controlled by N diffusion in binder phase.
► Thermodynamic predictions of N solubility levels in Fe–Ni–Co binders.