Two step aging treatment for Ni-Cr-Mo alloys
OwnerLee Pike, Jr., Dwaine L. Klarstrom +1inventors
InventorsLee Pike, Jr., Dwaine L. Klarstrom, Michael F. Rothman
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Abstract
A two step heat treatment for Ni—Cr—Mo alloys containing from 12% to 23.5% chromium provides higher yield strength, high tensile strength and other mechanical properties comparable to those observed in similar alloys age-hardened according to current practices. This treatment is done over a total time of not more than 50 hours. However, the treatment works for only those alloys having alloying elements present in amounts according to an equation here disclosed.
Claims10
A nickel-chromium-molybdenum alloy comprised in weight percent of:
- from 12% to 23.5% chromium;
- from 13% to 23% molybdenum;
- from 0.12% to 0.2% aluminum;
- from 0.002% to 0.006% carbon;
- from 0.30% to 0.34% manganese;
- from 1.0% to 1.7% iron;
- from 0.05% to 0.8% cobalt;
- from 0.10% to 0.34% tungsten;
- and
- from 0.002% to 0.005% boron;
- wherein the alloy has a P value of from 31.2 to 35.9, P being defined as:
- P=2.46 Al+0.19 Co+0.83 Cr−0.16 Cu+0.39 Fe+0.59 Mn+1.0 Mo+0.81 Zr+2.15 Si+1.06 V+0.39 W+0.68 Nb+0.52 Hf+0.45 Ta+1.35 Ti
- and the alloy is processed with a two step heat treatment comprised of:
- aging the alloy at about 1275° F. to about 1400° F. for at least 8 hours;
- cooling the alloy to a temperature of from about 1000° F. to about 1325° F.;
- maintaining the alloy within that temperature range for at least 8 hours;
- and
- cooling the alloy to room temperature.
A method for treating alloy having a composition comprised in weight percent of from 12% to 23.5% chromium, from 13% to 23% molybdenum, up to about 0.5% aluminum, up to 0.02% carbon, up to about 1.5% manganese, up to about 3% iron, up to about 2.5% cobalt, up to about 4.5% tungsten, up to about 0.015% boron, up to about 1.25% niobium;
- up to about 0.75% silicon;
- up to about 2.2% tantalum;
- up to about 0.7% titanium and the balance nickel plus impurities, wherein the alloy has a P value of from 31.2 to 35.9, P being defined as:
- P=2.46 Al+0.19 Co+0.83 Cr−0.16 Cu+0.39 Fe+0.59 Mn+1.0 Mo+0.81 Zr+2.15 Si+1.06 V+0.39 W+0.68 Nb+0.52 Hf+0.45 Ta+1.35 Ti
- the method comprised of:
- aging the alloy at about 1275° F. to about 1400° F. for at least 8 hours;
- cooling the alloy to a temperature of from about 1000° F. to about 1325° F.;
- maintaining the alloy within that temperature range for at least 8 hours without working the alloy between any of these steps;
- and
- cooling the alloy to room temperature.
Dependencies are inferred from the claim text.