Cobalt-base alloys

Claim 1

A cobalt-base alloy having a hexagonal close-packed platelet phase dispersed in a face-centered cubic matrix phase, said alloy being substantially free of embrittling phases and consisting essentially of the following elements in percent by weight: Carbon 0 - 0.05 Nickel 18 - 40 Molybdenum6 - 12Chromium 15 - 25 Iron 6 - 25 Boron 0 - 0.1 Titanium 0 or 1-5 Aluminum 0 or 0-1 Columbium 0 or 0-2 Cobalt Balance, said alloy either being free of titanium, aluminum, and columbium, or comprising 1 - 5 percent by weight of titanium together with at least aluminum or columbium and not more than 10 percent by weight of iron, the electron vacancy number of the alloy, Nv, defined by Nv 0.61 Ni + 1.71 Co + 2.66 Fe + 4.66 Cr + 5.66 Mo, wherein the chemical symbols represent the effective atomic fractions (as defined) of the respective element present in the alloy, being no greater than 2.55 in those alloys containing from 16 to 25 percent by weight of iron and not exceeding the value Nv 2.82 - 0.017 WFe , where WFe is the percent by weight of iron in the alloy, in those alloys containing from 6 to 16 percent by weight of iron; said alloy having been homogenized by heating at 2,050* - 2,150* F., then haVing been cold-worked at a temperature below the hcp-fcc transformation zone to achieve a reduction in cross-section between about 5 percent and about 70 percent, and then having been heat-aged at 800* - 1,350* F.

Claim 2

The method of making a cobalt-base alloy having a hexagonal close-packed platelet phase dispersed in a face-centered cubic matrix phase, said alloy being substantially free of embrittling phases, which comprises forming a melt consisting essentially of the following elements in percent by weight: Carbon 0 - 0.05 Nickel 18 - 40 Molybdenum 6 - 12 Chromium 15 -25 Iron 6 - 25 Boron 0 - 0.1 Titanium 0 or 1-5 Aluminum 0 or 0-1 Columbium 0 or 0-2 Cobalt Balance, said alloy either being free of titanium, aluminum, and columbium, or comprising 1 - 5 percent by weight of titanium together with at least aluminum or columbium and not more than 10 percent by weight of iron, the electron vacancy number of the alloy, Nv, defined by Nv 0.61 Ni + 1.71 Co + 2.66 Fe + 4.66 Cr + 5.66 Mo, wherein the chemical symbols represent the effective atomic fractions (as defined) of the respective elements present in the alloy, being no greater than 2.55 in those alloys containing from 16 to 25 percent by weight of iron and not exceeding the value Nv 2.82 - 0.017 WFe , where WFe is the percent by weight of iron in the alloy, in those alloys containing from 6 to 16 percent by weight of iron; cooling said melt, and cold-working said alloy at a temperature below the lower temperature of the hcp-fcc phase-transformation zone to achieve a reduction in cross-section between about 5 percent and about 70 percent.

Claim 3

The method of making a cobalt-base alloy having a hexagonal close-packed platelet phase dispersed in a face-centered cubic matrix phase, said alloy being substantially free of embrittling phases, which comprises forming a melt consisting essentially of the following elements in percent by weight: Carbon 0 - 0.05 Nickel 18 - 40 Molybdenum 6 - 12 Chromium 15 -25 Iron 6 - 25 Boron 0 - 0.1 Titanium 0 or 1-5 Aluminum 0 or 0-1 Columbium 0 or 0-2 Cobalt Balance, said alloy either being free of titanium, aluminum, and columbium, or comprising 1 - 5 percent by weight of titanium together with at least aluminum or columbium and not more than 10 percent by weight of iron, the electron vacancy number of the alloy, Nv, defined by Nv 0.61 Ni + 1.71 Co + 2.66 Fe + 4.66 Cr + 5.66 Mo, wherein the chemical symbols represent the effective atomic fractions (as defined) of the respective elements present in the alloy, being no greater than 2.55 in those alloys containing from 16 to 25 percent by weight of iron and not exceeding the value Nv 2.82 - 0.017 WFe , where WFe is the percent by weight of iron in the alloy, in those alloys containing from 6 to 16 percent by weight of iron; cooling said melt; homogenizing said alloy by heating; cold working said alloy at a temperature below the lower temperature of the hcp-fcc phase-transformation zone to achieve a reduction in cross-section between about 5 percent and about 70 percent; and then heat-aging said cold-worked alloy.