Porous surface structures in biomedical Co-Cr-Mo alloy prepared by local dealloying in a metallic melt

A novel method for preparing nano/submicron porous surfaces in biomedical Co-Cr-Mo alloy is presented, which involves local dealloying in a pure Zn melt at 500-800 °C and selective removal of Zn-rich phase formed in the dealloying products. First, reaction layers composed of Zn-rich and Zn-lean phases were formed by partially dealloying of Co from the alloy, which thickness ranges from 6 μm to 90 μm. Then, various nano/submicron porous surface layers containing a small amount of Zn were introduced by selective removing the Zn-rich phase in 1 M HCl aqueous solution. The morphologies of either reaction layers or porous structures were significantly affected by dealloying temperature. The elements of Co, Cr, Mo and Zn in porous surface layers exist predominantly in their metallic states.