Abstract: This invention provides a technique for rendering bio-toxicity such as allergy toxicity derived from Ni trace impurity, i.e., nickel toxicity, which is unavoidably present in a bio-Co—Cr—Mo alloy or an Ni-free stainless steel alloy unharmful, characterized in that an element selected from the group consisting of the group 4, 5 and 13 elements of the periodic table, particularly an element selected from the group consisting of the group 4 elements of the periodic table, is added to the alloy composition. The additive element is preferably an element selected from the group consisting of zirconium and titanium, more preferably zirconium.

Abstract: A Co—Cr—Mo alloy with nitrogen addition composed of 26 to 35% by weight of Cr, 2 to 8% by weight of Mo, 0.1 to 0.3% by weight of N, and balance of Co is subjected to solution treatment and then subjected to isothermal aging treatment holding the alloy at 670 to 830° C. for a predetermined period of time to form a multi-phase structure composed of an ?-phase and a Cr nitride by means of an isothermal aging effect. After cooling, the alloy subjected to reverse transformation treatment in which the alloy is heated at a temperature range of 870 to 1100° C. for reverse transformation to a single ?-phase from the multi-phase structure composed of an ?-phase and a Cr nitride.

Abstract: A Co—Cr—Mo alloy with nitrogen addition composed of 26 to 35% by weight of Cr, 2 to 8% by weight of Mo, 0.1 to 0.3% by weight of N, and balance of Co is subjected to solution treatment and then subjected to isothermal aging treatment holding the alloy at 670 to 830° C. for a predetermined period of time to form a multi-phase structure composed of an ?-phase and a Cr nitride by means of an isothermal aging effect. After cooling, the alloy subjected to reverse transformation treatment in which the alloy is heated at a temperature range of 870 to 1100° C. for reverse transformation to a single ?-phase from the multi-phase structure composed of an ?-phase and a Cr nitride.

Abstract: This invention provides a technique for rendering bio-toxicity such as allergy toxicity derived from Ni trace impurity, i.e., nickel toxicity, which is unavoidably present in a bio-Co—Cr—Mo alloy or an Ni-free stainless steel alloy unharmful, characterized in that an element selected from the group consisting of the group 4, 5 and 13 elements of the periodic table, particularly an element selected from the group consisting of the group 4 elements of the periodic table, is added to the alloy composition. The additive element is preferably an element selected from the group consisting of zirconium and titanium, more preferably zirconium.

Abstract: This invention provides a technique for rendering bio-toxicity such as allergy toxicity derived from Ni trace impurity, i.e., nickel toxicity, which is unavoidably present in a bio-Co—Cr—Mo alloy or an Ni-free stainless steel alloy unharmful, characterized in that an element selected from the group consisting of the group 4, 5 and 13 elements of the periodic table, particularly an element selected from the group consisting of the group 4 elements of the periodic table, is added to the alloy composition. The additive element is preferably an element selected from the group consisting of zirconium and titanium, more preferably zirconium.