Cobalt-chromium-iron-nickel alloys amenable to nitride strengthening
A wroughtable, cobalt alloy capable of through thickness nitridation and strengthening using practical treatments and practical sheet thicknesses contains in weight percent about 23 to about 30% chromium, about 15 to about 25% iron, up to about 27.3% nickel, about 0.75 to about 1.7% titanium, about 0.85 to about 1.9% niobium or zirconium, up to 0.2% carbon, up to 0.015% boron, up to 0.015% rare earth elements, up to 0.5% aluminum, up to 1% manganese, up to 1% silicon, up to 1% tungsten, up to 1% molybdenum, and the balance cobalt plus impurities and the total weight percent of titanium plus niobium or equivalents is from about 1.6 to about 3.6.
1. A wroughtable, cobalt alloy capable of through thickness nitridation and strengthening consisting essentially of in weight percent:
about 23 to about 30% chromium
about 15 to about 25% iron
up to about 27.3% nickel
about 0.75 to about 1.7% titanium
about 0.85 to about 1.9% niobium, zirconium or a combination thereof
up to 0.2% carbon
up to 0.015% boron
up to 0.015% rare earth elements
up to 0.5% aluminum
up to 1% manganese
up to 1% silicon
up to 1% tungsten
up to 1% molybdenum, and
balance cobalt plus impurities
wherein titanium +niobium is from about 1.6 to about 3.6%.
2. The alloy of claim 1 wherein the alloy is in a wrought form having a thickness of up to 2 mm.
3. The alloy of claim 1 wherein the alloy has been subjected to a nitriding treatment.
4. The alloy of claim 3 wherein the nitriding treatment is comprised of:
heating the alloy for at least 48 hours in a nitrogen atmosphere at a temperature of 1,095° C.;
then heating the alloy for at least 1 hour in an argon atmosphere at 1,120° C.; and
then heating the alloy for at least 2 hours in an argon atmosphere at 1,205° C.
5. A wroughtable, cobalt alloy consisting essentially of in weight percent:
23.6 to 29.5% chromium
16.7 to 24.8% iron
0.56 to 27.3% nickel
0.75 to 1.7% titanium
0.85 to 1.92% niobium
up to 0.2% carbon
up to 0.012% boron
up to 0.015% rare earth elements
up to 0.5% aluminum
up to 0.92% manganese
up to 0.97% silicon
up to 1% tungsten
up to 1% molybdenum; and
balance cobalt plus impurities
wherein titanium +niobium is from about 1.6 to about 3.6%.
6. A wroughtable, cobalt alloy capable of through thickness nitridation and strengthening consisting essentially of in weight percent:
about 23 to about 30% chromium
about 15 to about 25% iron
up to about 27.3% nickel
at least one element selected from the group consisting of titanium, zirconium and hafnium such that:
0.75≦Ti+Zr/1.91+Hf/3.73≦1.7
at least one element selected from the group consisting of vanadium, niobium, zirconium and tantalum such that:
0.87≦Nb+Zr+V/1.98+Ta/1.98≦1.92
up to 0.2% carbon
up to 0.015% boron
up to 0.015% rare earth elements
up to 0.5% aluminum
up to 1% manganese
up to 1% silicon
up to 1% tungsten
up to 1% molybdenum, and
balance cobalt plus impurities
wherein the alloy further satisfying the following compositional relationship defined with elemental quantities being in terms of weight percent:
1.6≦Ti+1.52Zr+Hf/3.73+Nb+V/1.98+Ta/1.98≦3.6.
7. The alloy of claim 6 wherein the alloy contains in weight percent:
23.6 to 29% chromium
16.7 to 24.8% iron
0.56 to 27.3% nickel
0.75 to 1.7% titanium
0.85 to 1.92% niobium
up to 0.92 manganese, and
up to 0.97 silicon.
8. The alloy of claim 6 wherein zirconium is substituted for at least a portion of the niobium on a one to one basis.
9. The alloy of claim 6 wherein the alloy is in a wrought form having a thickness of up to 2 mm.
10. The alloy of claim 6 wherein the alloy has been subjected to a nitriding treatment.
11. The alloy of claim 10 wherein the nitriding treatment is comprised of:
heating the alloy for at least 48 hours in a nitrogen atmosphere at a temperature of 1,095° C.;
then heating the alloy for at least 1 hour in an argon atmosphere at 1,120° C.; and
then heating the alloy for at least 2 hours in an argon atmosphere at 1,205° C.