Fabrication and Mechanical Properties of Porous Co-Cr-Mo Alloy Compacts without Ni Addition

Porous Co-29Cr-6Mo (mass%) compacts without Ni were fabricated by hot pressing and their microstructure and mechanical properties were investigated. PREPed Co-29Mo-6Mo powder with a diameter range (300-500 (mu)m) was hot-pressed under the uniaxial pressure of 40 MPa at 1223 K for 7.2 ks. Hotpressed compacts were annealed at 1473 K for 7.2 ks for further sintering. X-ray diffraction analysis revealed that (epsilon) and (sigma) phases appeared dominantly in the PREPed powder, while (epsilon) and (sigma) phases coexisted in the compact which was hot-pressed at 1223 K. After annealing at 1473 K, only the (epsilon) phase was detected although the (gamma) phase was stable at this temperature. Therefore, the (epsilon) phase formed during furnace cooling. Tensile behavior of porous Co-29Cr-6Mo compacts was characterized by the stress-strain curves. The as-hot pressed compact showed linear deformation followed by sudden fracture. The annealed compact showed higher ultimate tensile strength (UTS) and lower yield strength than the as-hot pressed compact. Youngʹs modulus of the annealed compact was difficult to determine from the stress-strain curve. However, the annealed compact possessed a tensile strength of 116 MPa, which is comparable to that of human cortical bone.