Method of heat treating a superalloy article and article made thereby

Abstract

A method of heat treating a superalloy article is disclosed. The method includes hot-working an article comprising an superalloy to produce a hot-worked microstructure throughout the article; solution treating the article at a temperature and for a time sufficient to form a partially recrystallized warm-worked microstructure throughout the article; and cooling the article. The method also includes precipitation aging the article at a first precipitation aging temperature of about 1300° F. to about 1400° F. for a first duration of about 4 hours to about 12 hours; cooling the article to a second precipitation aging temperature; precipitation aging the article at a second precipitation aging temperature of about 1150° F. to about 1200° F. for a second duration of about 4 hours to about 12 hours; and cooling the article from the second precipitation aging temperature to an ambient temperature.

1 . A method of heat treating an article comprising an Ni-base superalloy having a hot-worked microstructure throughout the article:
 solution treating the article at a temperature and for a time sufficient to form a partially recrystallized, warm-worked microstructure throughout the article;   cooling the article;   precipitation aging the article at a first precipitation aging temperature of about 1300° F. to about 1400° F. for a first duration of about 4 hours to about 12 hours;   cooling the article to a second precipitation aging temperature;   precipitation aging the article at a second precipitation aging temperature of about 1150° F. to about 1200° F. for a second duration of about 4 hours to about 12 hours; and   cooling the article from the second precipitation aging temperature to an ambient temperature, wherein the Ni-base superalloy has the partially recrystallized, warm-worked bimodal, bimorphic microstructure throughout the article, and wherein the microstructure also comprises gamma prime and gamma double prime and wherein the bimodal, bimorphic microstructure comprises larger elongated grains interspersed with smaller equiaxed grains.   
     
     
         2 . The method of  claim 1 , wherein cooling the article further comprises:
 cooling the article to ambient temperature; and   reheating the article to the first precipitation aging temperature.   
     
     
         3 . The method of  claim 2 , wherein cooling the article comprises fan cooling the article to the ambient temperature. 
     
     
         4 . The method of  claim 1 , wherein cooling the article comprises fan cooling the article directly to the first precipitation aging temperature. 
     
     
         5 . The method of  claim 1 , wherein cooling the article to the second precipitation aging temperature comprises cooling the article at about 100° F./hr. 
     
     
         6 . The method of  claim 5 , wherein the cooling of the article to the second precipitation aging temperature comprises furnace cooling. 
     
     
         7 . The method of  claim 1 , wherein solution treating is performed at a temperature of about 1600° F. to about 1750° F. for about 1 to about 12 hours. 
     
     
         8 . The method of  claim 1 , wherein the superalloy comprises an NiCrMoNbTi superalloy. 
     
     
         9 . The method of  claim 8 , wherein the superalloy comprises, by weight: about 55.0-63.0% Ni, about 19.0-22.5% Cr, about 6.5-9.5% Mo, about 2.75-4.5% Nb, about 1.0-2.3% Ti, up to about 0.35% Al, up to about 0.35% Mn, up to about 0.20% Si, up to about 0.010% S, up to about 0.20% C and up to about 0.015% P, with the balance Fe and incidental or trace impurities. 
     
     
         10 . The method of  claim 1 , wherein the superalloy comprises an Ni-base superalloy comprising by weight about 19.0-22.5% Cr, about 6.5-9.5% Mo, about 2.75-4.5% Nb and about 1.0-2.3% Ti. 
     
     
         11 . The method of  claim 1 , wherein the Ni-base superalloy has a 0.2% yield strength of at least about 187 ksi at about room temperature and at least about 165 ksi at about 750° C., an RA of at least about 24% at about room temperature and at least about 31% at about 1150° C. and a hold time crack propagation resistance at about 593° C. in air and a stress intensity factor (k) where k=28 ksi-(in.) 1/2  of at least about 2400 hours. 
     
     
         12 . An article comprising an Ni-base superalloy and having a partially-recrystallized, warm-worked bimodal, bimorphic microstructure comprising gamma prime and gamma double prime throughout the article, wherein the bimodal, bimorphic microstructure comprises larger elongated grains interspersed with smaller equiaxed grains. 
     
     
         13 . The article of  claim 12 , wherein the superalloy comprises an NiCrMoNbTi superalloy. 
     
     
         14 . The article of  claim 13 , wherein the superalloy comprises, by weight: about 55.0-63.0% Ni, about 19.0-22.5% Cr, about 6.5-9.5% Mo, about 2.75-4.5% Nb, about 1.0-2.3% Ti, up to about 0.35% Al, up to about 0.35% Mn, up to about 0.20% Si, up to about 0.010% S, up to about 0.20% C and up to about 0.015% P, with the balance Fe and incidental or trace impurities. 
     
     
         15 . The article of  claim 12 , wherein the superalloy comprises an Ni-base superalloy comprising by weight about 19.0-22.5% Cr, about 6.5-9.5% Mo about 2.75-4.5% Nb and about 1.0-2.3% Ti. 
     
     
         16 . The article of  claim 12 , wherein the microstructure comprises adjacent grains having at least some grain misorientations greater than about 10 degrees. 
     
     
         17 . The article of  claim 12 , wherein the microstructure comprises adjacent grains having grain misorientations greater than about 20 degrees. 
     
     
         18 . The article of  claim 12 , wherein the article comprises a turbine component, the turbine component comprising a blade, vane, rotor, stator, spacer, shroud, liner, nozzle, steam valve or combustor. 
     
     
         19 . An article comprising an Ni-base superalloy and having a partially-recrystallized, warm-worked bimodal, bimorphic microstructure comprising gamma prime and gamma double prime throughout the article and a static crack propagation resistance in air of at least about 2400 hours at a temperature of about 1,100° F., wherein the bimodal, bimorphic microstructure comprises larger elongated grains interspersed with smaller equiaxed grains. 
     
     
         20 . The article of  claim 19 , wherein the article comprises a turbine component, the turbine component comprising a blade, vane, rotor, stator, spacer, shroud, liner, nozzle, steam valve or combustor.