Dispersion strengthened cobalt-chromium-molybdenum alloy produced by gas atomization
AssigneePfizer Hospital Products Group, Inc.
InventorsKathy K. Wang, Larry J. Gustavson, John H. Dumbleton
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Abstract
A dispersion strengthened cobalt-chromium-molybdenum alloy produced by gas atomization containing a fine oxide dispersion, and characterized, after fabrication by gas atomization, thermomechanical processing and further high temperature exposure, by excellent corrosion resistance, high fatigue strength, high ductility and high temperature stability; a process for producing said alloy and prostheses formed from said alloy.
Claims8
A high strength, corrosion-resistant, high temperature stable, consolidated, biocompatible, ductile alloy having homogeneously distributed dispersed oxides and fine, equiaxed grain structure after high temperature exposure, said alloy being produced by gas atomization and consisting essentially of the following percentage composition by weight:
- ______________________________________ chromium 26 to 30 molybdenum 5 to 7 manganese 0 to 1 silicon 0 to 1 iron 0 to 0.75 nickel 0 to 1.0 carbon 0 to 0.35 nitrogen 0 to 0.25 oxygen 0.003 to 0.20 oxide-forming metal 0.003 to 2.0 ______________________________________
- and the balance cobalt, apart from trace amounts of incidental impurities;
- in which the oxide-forming metal is a metal selected from the group consisting of magnesium, calcium, aluminum, yttrium, lanthanum, titanium and zirconium, which forms high temperature-stable, non-accretive, fine oxide particles which oxide has a free energy of formation greater than the oxide of the matrix metal and is homogeneously distributed in the dispersed phase;
- and said alloy after fabrication by gas atomization, thermomechanical processing and further high temperature exposure has an ultimate tensile strength of 160-200 k.s.i., a 0.2% offset yield strength of 75-100 k.s.i., an elongation of 37 to 60%, and a fatigue strength at 10.sup.7 cycles (Rotating Ream) of 70-95 k.s.i.
A process for producing a high strength, corrosion-resistant, high temperature stable, consolidated, biocompatible, ductile alloy having homogeneously distributed dispersed oxides and fine, equiaxed grain structure after high temperature exposure, which comprises melting under an atmosphere consisting of nitrogen, an inert gas or a mixture thereof an alloy mixture consisting essentially of the following percentage composition by weight:
- ______________________________________ chromium 26 to 30 molybdenum 5 to 7 manganese 0 to 1 silicon 0 to 1 iron 0 to 0.75 nickel 0 to 1.0 carbon 0 to 0.35 nitrogen 0 to 0.25 oxygen 0.003 to 0.20 oxide-forming metal 0.003 to 2.0 ______________________________________
- and the balance cobalt, apart from trace amounts of incidental impurities;
- in which the oxide-forming metal is a metal selected from the group consisting of magnesium, calcium, aluminum, yttrium, lanthanum, titanium and zirconium, which forms high temperature-stable, non-accretive, fine oxide particles, which oxide has a free energy of formation greater than the oxide of the matrix metal and is homogeneously distributed in the dispersed phase wherein the cobalt, chromium, molybdenum and carbon are charged first, the resulting charge is flooded with nitrogen and/or inert gas and melted at a temperature within the range of 1454.degree. C. (2650.degree. F.) to 1538.degree. C. (3800.degree. F.), followed by addition of the oxide-forming metal, which acts as a getter for oxygen present in the original mixture and thus providing dispersed oxide, the nitrogen being present as nitride, derived from the nitrogenous atmosphere;
- immediately subjecting the molten mixture to gas atomization to produce a fine oxide dispersion homogeneously distributed throughout the alloy and thermomechanically processing the resultant alloy powder to provide a consolidated alloy having an ultimate tensile strength of 160-200 k.s.i., a 0.2% offset yield strength of 75-100 k.s.i., an elongation of 37 to 60%, and a fatigue strength at 10.sup.7 cycles (Rotating Beam) of 70-95 k.s.i.
Dependencies are inferred from the claim text.