Methods for processing nanostructured ferritic alloys, and articles produced thereby

Abstract

A method of forming an article including a nanostructured ferritic alloy is provided. The method provides steps for substantially inhibiting grain growth of a workpiece that includes nanostructured ferritic alloy, during heating and deforming at high temperatures and at high strain rates. Advantageously, the article is formed via conventional high strain rate techniques and thus, cost savings are provided. Articles are also provided which are formed by the method, and the articles so produced exhibit good mechanical properties at high operating temperatures, and thus are utilized as turbomachinery components, and in particular, component of a heavy duty gas turbine or steam turbine. A turbomachinery component comprising an NFA is provided.

1 . A method comprising:
 introducing a quantity of strain into a workpiece at a first temperature below about 1900 degrees Fahrenheit to form a strained workpiece;   heating the strained workpiece to a second temperature, wherein the second temperature is at least about 1900 degrees Fahrenheit; and   deforming the strained workpiece at the second temperature,
 wherein the workpiece comprises a nanostructured ferritc alloy (NFA), and wherein the quantity of strain introduced into the workpiece at the first temperature is effective to substantially inhibit grain growth in the strained workpiece during the heating and the deforming at the second temperature. 
   
     
     
         2 . The method of  claim 1 , wherein the workpiece comprises a grain size distribution having an average grain size less than about 2 microns. 
     
     
         3 . The method of  claim 1 , wherein introducing a quantity of strain into the workpiece at the first temperature comprises applying at least about 40 percent strain. 
     
     
         4 . The method of  claim 1 , wherein introducing a quantity of strain into the workpiece at the first temperature comprises deforming the workpiece at a strain rate lower than about 1 inch/inch/sec. 
     
     
         5 . The method of  claim 1 , wherein the first temperature ranges from about 1600 degrees Fahrenheit to 1900 degrees Fahrenheit. 
     
     
         6 . The method of  claim 1 , wherein the second temperature ranges from about 1950 degrees Fahrenheit to about 2300 degrees Fahrenheit. 
     
     
         7 . The method of  claim 1 , wherein deforming the strained workpiece comprises deforming the strained workpiece at a strain rate of at least about 1 inch/inch/sec. 
     
     
         8 . The method of  claim 1 , wherein deforming the strained workpiece comprises deforming the strained workpiece at a strain rate ranging from about 1 inch/inch/sec to about 30 inch/inch/sec. 
     
     
         9 . The method of  claim 1 , wherein the deforming step is performed by compaction, forging, extusion, or rolling. 
     
     
         10 . An article formed by the method according to  claim 1 . 
     
     
         11 . The article of  claim 10 , wherein the article is a turbomachinery component. 
     
     
         12 . A method of forming a turbomachinery component, comprising the steps of:
 introducing a quantity of strain into a workpiece at a first temperature below 1900 degrees Fahrenheit to form a strained workpiece, wherein the workpiece comprises a nano structured ferritc alloy (NFA);
 heating the strained workpiece to a second temperature, wherein the second temperature is at least about 1900 degrees Fahrenheit; and 
 forging the strained workpiece at the second temperature at a strain rate of at least about 1 inch/inch/sec,
 wherein the quantity of strain introduced into the workpiece at the first temperature is effective to substantially inhibit grain growth in the strained workpiece during the heating and the forging at the second temperature.