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Methods for processing alloys

  • US 9,869,003 B2
  • Filed: 02/26/2013
  • Issued: 01/16/2018
  • Est. Priority Date: 02/26/2013
  • Status: Active Grant
First Claim
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1. A method of processing a workpiece to inhibit precipitation of intermetallic compounds, the method comprising:

  • at least one of thermomechanically working and cooling a workpiece including an austenitic alloy, wherein during the at least one of thermomechanically working and cooling the workpiece, the austenitic alloy is at temperatures in a temperature range spanning a temperature just less than a calculated sigma solvus temperature of the austenitic alloy down to a cooling temperature for a time no greater than a critical cooling time;

    wherein the austenitic alloy comprises, in weight percentages based on total alloy weight, up to 0.2 carbon, up to 20 manganese, 0.1 to 1.0 silicon, 14.0 to 28.0 chromium, 15.0 to 25.43 nickel, 2.0 to 9.0 molybdenum, 0.1 to 3.0 copper, 0.08 to 0.9 nitrogen, 0.1 to 5.0 tungsten, 0.5 to 5.0 cobalt, up to 1.0 titanium, up to 0.05 boron, up to 0.05 phosphorus, up to 0.05 sulfur, 0.01 to 1.0 vanadium, 20 to 60 iron, and incidental impurities;

    wherein the calculated sigma solvus temperature is a function of the composition of the austenitic alloy in weight percentages and, in Fahrenheit degrees, is equal to 1155.8−

    (760.4)·

    (nickel/iron)+(1409)·

    (chromium/iron)+(2391.6)·

    (molybdenum/iron)−

    (288.9)·

    (manganese/iron)−

    (634.8)·

    (cobalt/iron)+(107.8)·

    (tungsten/iron);

    wherein the cooling temperature is a function of the composition of the austenitic alloy in weight percentages and, in Fahrenheit degrees, is equal to 1290.7−

    (604.2)·

    (nickel/iron)+(829.6)·

    (chromium/iron)+(1899.6)·

    (molybdenum/iron)−

    (635.5)·

    (cobalt/iron)+(1251.3)·

    (tungsten/iron); and

    wherein the critical cooling time is a function of the composition of the austenitic alloy in weight percentages and, in minutes, is equal to, in log10, 2.948+(3.631)·

    (nickel/iron)−

    (4.846)·

    (chromium/iron)−

    (11.157)·

    (molybdenum/iron)+(3.457)·

    (cobalt/iron)−

    (6.74)·

    (tungsten/iron), and wherein the critical cooling time is in a range of 10 minutes to 30 minutes.

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