Diffusion bonding of Ti–2.5Al–2.5Mo–2.5Zr and Co–Cr–Mo alloys

A solid state diffusion bonding between two metallic biomaterials, Ti–2.5Al–2.5Mo–2.5Zr alloy and Co–Cr–Mo alloy (F75), has been investigated by using energy-dispersive spectrometer analysis, metallographic observation and bonding strength evaluation. The experiments indicate that bonded at 750 °C leads to insufficient atoms diffusion and weak bond. When bonded at 900 °C some intermetallics, CoTi2, Co2Ti, and Cr2Ti, form in the diffusion zone, which significantly deteriorate the plasticity and lead to lower bonding strength. A high bonding strength can be achieved when bonding at 850 °C for 60 min. During the bonding process each element exhibits various diffusion velocity in the opposite alloy. The diffusion coefficients for those elements can be ranked in following sequence: DCo > DCr > DMo in the Ti–2.5Al–2.5Mo–2.5Zr alloy and DTi > DAl > DZr in the Co–Cr–Mo alloy.

► Optimized diffusion temperature and holding time for the solid state diffusion between Ti–2.5Al–2.5Mo–2.5Zr and Co–Cr–Mo.
► Evaluation of the diffusion coefficients of those elements in the counterpart alloys.
► Bonding at temperature higher than 850 °C results in the formation of CoTi2, Co2Ti, and Cr2Ti in the diffusion zone.