Nickel-based alloy, method and use

Abstract

Manufacturing method of a nickel-based alloy comprising the steps of forging and solution treating a metal mass of the composition described, subjecting the product to a first step of ageing at a higher temperature and a step of cooling in air, to a second step of ageing at a lower temperature and a step of cooling in air to obtain the nickel-based alloy. As a result of steps i)-v)), said alloy comprises metal hardening phases precipitated uniformly throughout its grains. The invention further relates to nickel-based alloys and a use of such alloys.

1 . Manufacturing method of a nickel-based alloy comprising the steps of:
 i) forging and solution treating a metal mass comprising, expressed as percentages by weight: C=0.030 max, Si=0.50 max, Mn 0.50 max, Cr=20.0-24.0, Ni=55.0-60.0, Mo=5.5-7.0, S=0.005 max, P=0.015 max, Cu=1.0 max, Co=1.0 max, Al=0.80 max, Ti=0.50-1.50, Nb=4.0-5.5 and Fe for the remaining percentage;   ii) subjecting the product of step i) to a first aging step at a higher temperature;   iii) cooling the product of step ii) in air;   iv) subjecting the product of step iii) to a second aging step at a lower temperature;   v) cooling in air the product of step iv) to obtain the nickel-based alloy.   wherein, following said steps i)-v), the hardening metal phases of the nickel-based alloy are precipitated in a uniform manner in the grains of the latter.   
     
     
         2 . Method of  claim 1 , wherein following the steps i)-v), the nickel-based alloy comprises metal hardening phases γ′ and γ″ precipitated in an essentially non-intergranular position, and carbide phases precipitated in a discontinuous manner at least along the boundary of said grains. 
     
     
         3 . Method of  claim 1 , further comprising the steps of:
 separating the product of step iii), and   transforming a first part of the separated product into a first finished product, for example with lower performances.   
     
     
         4 . Method of  claim 3 , further comprising a step of:
 sending to step iv) and subsequently to step v) a second part of said separated product to obtain a second product, of higher performance, made of said nickel-based alloy.   
     
     
         5 . Method of  claim 1 , wherein step iii) is characterized by a yield strength, measured at ambient temperature, of approximately 827 MPa or more and wherein, following step v), the nickel-based alloy is characterized by a yield strength, measured at ambient temperature, of approximately 950-970 MPa. 
     
     
         6 . Method of  claim 1 , wherein the metal mass forged and solution treated in step i) comprises, expressed as percentages by weight: C=0.022 max, Si=0.20 max, Mn=0.20 max, Cr=21.0-23, Ni=57.0-59.0, Mo 5.5-6.0, Al=0.30-0.60, Ti=0.70-1.0, Nb=4.5-5.0, Fe=5 as a minimum percentage. 
     
     
         7 . Method of  claim 1 , wherein the metal mass forged and solution treated in step i) comprises, expressed as percentages by weight: Ni=58, Cr=21.5, Mo=5.8, Nb=4.8, Ti=0.9, Al=0.4, Fe=8%. 
     
     
         8 . Method of  claim 1 , wherein step ii) is performed at a temperature of about 720-780° C. for about 3-8 hours, or for about 3-6 hours. 
     
     
         9 . Method of  claim 1 , wherein step iv) is performed at a temperature of 600-640° C. for about 4-10 hours. 
     
     
         10 . Method of  claim 1 , wherein step i) comprises the steps of:
 forging the metal mass at a temperature of approximately 1000-1160° C., and   then solution treating said mass at a temperature of approximately 1030-1080° C., said step of solution treating being followed by a cooling step in water before step ii).   
     
     
         11 . Method of  claim 1 , wherein steps of cooling iii) and v) are carried out in air at ambient temperature, namely at a temperature outside the heated environment in which the aging steps ii) and iv) are performed, to about an ambient temperature of the respective products. 
     
     
         12 . Nickel-based alloy obtained by means of the steps:
 i) forging and solution treating a metal mass comprising, expressed as percentages by weight: C=0.030 max, Si=0.50 max, Mn=0.50 max, Cr=20.0-24.0, Ni=55.0-60.0, Mo=5.5-7.0, S=0.005 max, P=0.015 max, Cu=1.0 max, Co=1.0 max, Al=0.80 max, Ti=0.50-1.50, Nb=4.0-5.5 and Fe for the remaining percentage;   ii) subjecting the product of step i) to a first aging step at a higher temperature;   iii) cooling the product of step ii) in air;   iv) subjecting the product of step iii) to a second aging step at a lower temperature;   v) cooling in air the product of step iv) to obtain the nickel-based alloy;   wherein, following steps i)-v)), the nickel-based alloy comprises metal hardening phases precipitated uniformly throughout its grains.   
     
     
         13 . Alloy of  claim 12 , wherein following steps i)-v), the nickel-based alloy comprises metal hardening phases γ′ and γ″ precipitated in an essentially non-intergranular position, and carbide phases precipitated in a discontinuous manner at least along the boundary of said grains. 
     
     
         14 .- 15 . (canceled) 
     
     
         16 . Nickel-based alloy made by the method of  claim 1 , comprising a metal mass comprising, expressed in percentages by weight: C=0.030 max, Si=0.50 max, Mn=0.50 max, Cr=20.0-24.0, Ni=55.0-60.0, Mo=5.5-7.0, S=0.005 max, P=0.015 max, Cu=1.0 max, Co=1.0 max, Al=0.80 max, Ti=0.50-1.50, Nb=4.0-5.5 and Fe for the remaining percentage; said alloy being characterized in that it comprises metal hardening phases γ′ and γ″ precipitated in an essentially non-intergranular position, and carbide phases precipitated in a discontinuous manner at least along the boundary of said grains. 
     
     
         17 . Use of the alloy of  claim 12  for making equipment and pipes for the chemical or petrol industries. 
     
     
         18 . Manufacturing method of a nickel-based alloy, comprising the steps of:
 i) forging and solution treating a metal mass comprising, expressed as percentages by weight: C=0.030 max, Si=0.50 max, Mn 0.50 max, Cr=20.0-24.0, Ni=55.0-60.0, Mo=5.5-7.0, S=0.005 max, P=0.015 max, Cu=1.0 max, Co=1.0 max, Al=0.80 max, Ti=0.50-1.50, Nb=4.0-5.5 and Fe for the remaining percentage;   ii) subjecting the product of step i) to a first aging step at a higher temperature;   iii) cooling the product of step ii) in air;   iv) subjecting the product of step iii) to a second aging step at a lower temperature;   v) cooling in air the product of step iv) to obtain the nickel-based alloy.   wherein, following said steps i) to v), the hardening metal phases of the nickel-based alloy are precipitated in a uniform manner in the grains of the latter and wherein following the steps i) to v), the nickel-based alloy comprises metal hardening phases γ′ and γ″ precipitated in an essentially non-intergranular position, and carbide phases precipitated in a discontinuous manner at least along the boundary of said grains.   
     
     
         19 . Method of  claim 18 , further comprising the steps of:
 separating the product of step iii), and   transforming a first part of the separated product into a first finished product, for example with lower performances.   
     
     
         20 . Method of  claim 18 , wherein the metal mass forged and solution treated in step i) comprises, expressed as percentages by weight: C=0.022 max, Si=0.20 max, Mn=0.20 max, Cr=21.0-23, Ni=57.0-59.0, Mo 5.5-6.0, Al=0.30-0.60, Ti=0.70-1.0, Nb=4.5-5.0, Fe=5 as a minimum percentage. 
     
     
         21 . Method of  claim 18 , wherein the metal mass forged and solution treated in step i) comprises, expressed as percentages by weight: Ni=58, Cr=21.5, Mo=5.8, Nb=4.8, Ti=0.9, Al=0.4, Fe=8%, wherein step ii) is performed at a temperature of about 720-780° C. for about 3-8 hours, or for about 3-6 hours, and wherein step iv) is performed at a temperature of 600-640° C. for about 4-10 hours. 
     
     
         22 . Method of  claim 18 , wherein step i) further comprises the steps of:
 forging the metal mass at a temperature of approximately 1000-1160° C., and   then solution treating said mass at a temperature of approximately 1030-1080° C., said step of solution treating being followed by a cooling step in water before step ii)