Role of nitrogen addition in stabilizing the γ phase of Biomedical Co–29Cr–6Mo alloy

Three-dimensional atom probe observations and thermodynamic calculations revealed that the mechanism of γ-phase stabilization by N addition in the Co–29Cr–6Mo alloy is different from that in stainless steel: N addition does not lower the free energy of the γ phase in Co–29Cr–6Mo but increases the energy barrier and thus lowers the kinetic rate of the γ → ɛ transition through the formation of Cr–N short range order.

► 3-D atomic probe observation + thermodynamic calculations.
► N addition does not change the Gibbs energy of alloy system greatly.
► Generate the energy barrier by formation of N–Cr cluster.
► N addition stabilizes the γ phase of Co–Cr–Mo alloy.
► Phase transition slows down but the transition point does not change with N addition.