Corrosion-resistant alloy composition

Abstract

An alloy composition includes 40-60 wt. % of a nickel-based superalloy and 40-60 wt. % of a cobalt-based superalloy based on the total weight of the alloy composition. The nickel-based superalloy includes 40-60 wt. % of nickel and 15-25 wt. % of chromium based on the total weight of the nickel-based superalloy. The cobalt-based superalloy includes 50-70 wt. % of cobalt and 25-35 wt. % of chromium based on the total weight of the cobalt-based superalloy. The nickel-based superalloy and the cobalt-based superalloy are homogeneously distributed in the alloy composition. Further, the alloy composition is a spark plasma product of spherical particles having an average particle size of 10 micrometers (μm) to 45 μm of the nickel-based superalloy and particles having an average particle size of 5-40 μm of the cobalt-based superalloy. The alloy composition is more corrosion-resistant than a pure nickel-based superalloy and a pure copper-based superalloy.

1 . An alloy composition, comprising:
 40-60 wt. % a nickel-based superalloy; and   40-60 wt. % a cobalt-based superalloy based on a total weight of the alloy composition, wherein   the nickel-based superalloy comprises 40-60 wt. % of nickel and 15-25 wt. % of chromium based on a total weight of the nickel-based superalloy,   the cobalt-based superalloy comprises 50-70 wt. % of cobalt and 25-35 wt. % of chromium based on a total weight of the cobalt-based superalloy,   the nickel-based superalloy and the cobalt-based superalloy are homogeneously distributed in the alloy composition, and   the alloy composition is a spark plasma product of spherical particles having an average particle size of 15 to 45 μm of the nickel-based superalloy and particles having an average particle size of 5 to 40 μm of the cobalt-based superalloy.   
     
     
         2 . The alloy composition of  claim 1 , wherein:
 the nickel-based superalloy comprises Inconel 718, and   the cobalt-based superalloy comprises Co 212.   
     
     
         3 . The alloy composition of  claim 2 , wherein the Inconel 718 comprises:
 52.4 wt. % of Ni;   18.85 wt. % of Cr;   4.96 wt. % of Nb and Ta in total,   3.09 wt. % of Mo;   0.95 wt. % of Ti;   0.48 wt. % of Al;   0.05 wt. % of Co;   0.04 wt. % of Si;   0.04 wt. % of C;   0.02 wt. % of Mn;   0.02 wt. % of Cu; and   Fe, based on the total weight of the nickel-based superalloy.   
     
     
         4 . The alloy composition of  claim 3 , wherein the Co 212 comprises:
 28.5 wt. % of Cr;   6 wt. % of Mo;   0.75 wt. % of Fe;   0.35 wt. % of C;   1.0 wt. % or less of Ni;   1.0 wt. % or less of Si;   1.0 wt. % or less of Mn; and   Co, based on the total weight of the cobalt-based superalloy.   
     
     
         5 . The alloy composition of  claim 4 , wherein:
 the Inconel 718 and the Co 212 has a weight ratio of 1:1 in the alloy composition.   
     
     
         6 . The alloy composition of  claim 5 , wherein:
 the alloy composition is more corrosion-resistant than a pure Inconel 718 alloy and a pure Co 212 alloy.   
     
     
         7 . The alloy composition of  claim 6 , wherein:
 the alloy composition has a corrosion rate (CR) of about 6.04×10 −3  mils per year (mpy) in a solution containing 3.5 wt. % of NaCl for an open circuit potential of ±10 mV, and   the CR of the alloy composition is 55%-75% lower than those of the pure Inconel 718 alloy and the pure Co 212 alloy.   
     
     
         8 . The alloy composition of  claim 6 , wherein:
 the alloy composition has a corrosion current density (I corr ) of about 41.5 nA in a solution containing 3.5 wt. % of NaCl for an open circuit potential of ±10 mV, and   the Icorr of the alloy composition is 55%-75% lower than those of the pure Inconel 718 alloy and the pure Co 212 alloy.   
     
     
         9 . The alloy composition of  claim 6 , wherein:
 the alloy composition has a polarization resistance (Rp) of about 628.1 kΩ in a solution containing 3.5 wt. % of NaCl for an open circuit potential of ±10 mV, and   the R p  of the alloy composition is 150%-270% higher than those of the pure Inconel 718 alloy and the pure Co 212 alloy.   
     
     
         10 . The alloy composition of  claim 6 , wherein:
 corrosion protectiveness of the alloy composition is 150%-200% higher than those of the pure Inconel 718 alloy and the pure Co 212 alloy.   
     
     
         11 . The alloy composition of  claim 1 , wherein:
 the nickel-based superalloy and the cobalt-based superalloy form separate phases that are homogeneously distributed in the alloy composition.   
     
     
         12 . The alloy composition of  claim 11 , wherein:
 an interface between the separate phases has no secondary phases, reaction products, de-bonded areas or voids.   
     
     
         13 . The alloy composition of  claim 11 , wherein:
 the separate phases have an average dimension of 20 to 60 μm.   
     
     
         14 . The alloy composition of  claim 1 , wherein the alloy composition is obtained by:
 obtaining powders of Inconel 718 and powders of Co 212 by gas atomization;   forming a mixture of the powders of Inconel 718, the powders of Co 212 and ethanol in an ultrasonic probe sonicator;   removing the ethanol from the mixture by heating the mixture; and   densifying the mixture by spark plasma sintering.   
     
     
         15 . The alloy composition of  claim 14 , wherein:
 the spark plasma sintering is executed at a pressure of 50 MPa and a temperature of 1100° C. for 15 minutes, with a heating rate of 100° C./min.   
     
     
         16 . The alloy composition of  claim 14 , wherein obtaining the alloy composition further comprises:
 grinding the mixture on a diamond disk to remove a graphite film used in the spark plasma sintering;   grinding the mixture with a SiC sandpaper of 120 to 180 grit;   polishing the mixture on a polishing cloth with a diamond paste solution; and   rinse the mixture with ethanol.   
     
     
         17 . The alloy composition of  claim 14 , wherein:
 the powders of Inconel 718 have an average particle size of 15 to 45 μm as a result of the gas atomization, and   the powders of Co 212 have an average particle size of 10 to 20 μm as a result of the gas atomization.   
     
     
         18 . The alloy composition of  claim 14 , wherein:
 the gas atomization is executed with argon.   
     
     
         19 . The alloy composition of  claim 14 , wherein:
 the mixture is heated at 70° C. for 24 hours to remove the ethanol from the mixture.   
     
     
         20 . The alloy composition of  claim 1 , wherein:
 the nickel-based superalloy is Inconel 718,   the cobalt-based superalloy is Co 212, and   the alloy composition consists of about 50 wt. % of Inconel 718 and about 50 wt. % of Co 212 based on the total weight of the alloy composition.