Corrosion resistant metallurgical powder compositions, methods, and compacted articles

Abstract

Provided are corrosion resistant metallurgical powder compositions, corrosion resistant compacted articles prepared from metallurgical powder compositions, and methods of preparing the same. Corrosion resistant metallurgical powder compositions include as a major component, an iron-based powder and, as a minor component, alloy additives that include chromium, and carbon. Upon compaction and sintering, the iron-based powder and alloy additives form a dual phase alloy system. The dual phase alloy system is denoted by an admixed martensite and ferrite microstructure. This unique microstructure results in beneficial physical properties, such as for example, high strength, hardness, and ductility, impact energy, and fatigue endurance, while maintaining resistance to corrosion.

1 . A corrosion resistant metallurgical powder composition comprising: 
 (a) as a major component, an iron-based powder,    (b) as a minor component, alloy additives comprising: 
 about 5.0 to about 30.0 weight percent chromium, and  
 about 0.001 to about 0.1 weight percent carbon,  
   wherein the corrosion resistant metallurgical powder composition achieves a dual phase microstructure of martensite and ferrite upon compaction and sintering.    
   
   
       2 . The corrosion resistant metallurgical powder composition of  claim 1  further comprising alloying additives comprising molybdenum, copper, nickel, sulfur, phosphorus, silicon, manganese, titanium, aluminum, or combinations thereof.  
   
   
       3 . The corrosion resistant metallurgical powder composition of  claim 2  wherein the metallurgical powder composition comprises a prealloyed powder.  
   
   
       4 . The corrosion resistant metallurgical powder composition of  claim 1  wherein the ferrite factor is from about 6 to about 20 and ferrite factor (K m ) is defined by the formula:  
         K   m =(weight percent Cr)−40(weight percent C+weight percent N)+4(weight percent Mo)−5(weight percent Cu)−4(weight percent Ni)−20(weight percent P)+6(weight percent Si)−2(weight percent Mn)+8(weight percent Ti)+2(weight percent Al).  
   
   
       5 . The corrosion resistant metallurgical powder composition of  claim 1  wherein the iron based powder is a water-atomization powder.  
   
   
       6 . The corrosion resistant metallurgical powder composition of  claim 1  further comprising 
 about 0.01 to about 1.0 weight percent molybdenum,    about 0.01 to about 1.0 weight percent copper,    about 0.0 to about 2.0 weight percent nickel,    about 0.0 to about 0.1 weight percent sulfur,    about 0.0 to about 0.1 weight percent phosphorus,    about 0.0 to about 1.5 weight percent silicon,    about 0.0 to about 0.5 weight percent manganese,    about 0.0 to about 0.2 weight percent titanium,    about 0.0 to about 0.1 weight percent aluminum, or    combinations thereof.    
   
   
       7 . The corrosion resistant metallurgical powder composition of  claim 1  wherein the alloy additives comprise: 
 about 11.0 to about 13.0 weight percent chromium,    about 0.001 to about 0.03 weight percent carbon,    about 0.2 to about 0.5 weight percent molybdenum,    about 0.2 to about 0.5 weight percent copper,    about 0.0 to about 1.5 weight percent nickel,    about 0.0 to about 0.03 weight percent sulfur,    about 0.0 to about 0.03 weight percent phosphorus,    about 0.0 to about 1.0 weight percent silicon,    about 0.0 to about 0.25 weight percent manganese, and,    about 0.0 to about 0.05 weight percent titanium    about 0.0 to about 0.05 weight percent aluminum, or    combinations thereof.    
   
   
       8 . A corrosion resistant compacted article comprising a metallurgical powder composition comprising: 
 (a) as a major component, an iron-based powder,    (b) as a minor component, alloy additives comprising: 
 about 5.0 to about 30.0 weight percent chromium,  
 about 0.001 to about 0.1 weight percent carbon,  
   wherein the compacted article achieves a dual phase microstructure upon sintering.    
   
   
       9 . The corrosion resistant compacted article of  claim 8  wherein the metallurgical powder composition further comprises molybdenum, copper, nickel, sulfur, phosphorus, silicon, manganese, titanium, aluminum, or combinations thereof.  
   
   
       10 . The corrosion resistant compacted article of  claim 9  wherein the metallurgical powder composition comprises a prealloyed powder.  
   
   
       11 . The corrosion resistant compacted article of  claim 8  wherein the ferrite factor of the metallurgical powder composition is from about 6 to about 20 and ferrite factor (K m ) is defined by the formula:  
         K   m =(weight percent Cr)−40(weight percent C+weight percent N)+4(weight percent Mo)−5(weight percent Cu)−4(weight percent Ni)−20(weight percent P)+6(weight percent Si)−2(weight percent Mn)+8(weight percent Ti)+2(weight percent Al).  
   
   
       12 . The corrosion resistant compacted article of  claim 8  wherein the compacted article is sintered and has a dual phase microstructure of martensite and ferrite.  
   
   
       13 . The corrosion resistant compacted article of  claim 8  wherein the compacted article is sintered and is composed of from about 1.0 to about 20.0 volume percent of ferrite in a martensite matrix.  
   
   
       14 . The corrosion resistant compacted article of  claim 8  wherein the compacted article exhibits a density of greater than about 6.6 g/cm 3 .  
   
   
       15 . A method of preparing corrosion resistant compacted articles comprising the steps of: 
 (a) providing a metallurgical powder composition comprising: 
 (i) as a major component, an iron-based powder,  
 (ii) as a minor component, alloy additives comprising: 
 about 5.0 to about 30.0 weight percent chromium, and  
 about 0.001 to about 0.1 weight percent carbon,  
 
   (b) compacting the metallurgical powder composition in a die at a pressure of at least 5 tsi;    wherein the metallurgical powder composition achieves a dual phase microstructure of martensite and ferrite upon sintering.    
   
   
       16 . The method of preparing corrosion resistant compacted articles of  claim 15  wherein the metallurgical powder composition further comprises molybdenum, copper, nickel, sulfur, phosphorus, silicon, manganese, titanium, aluminum, or combinations thereof.  
   
   
       17 . The method of preparing corrosion resistant compacted articles of  claim 15  wherein the metallurgical powder composition comprises a prealloyed powder.  
   
   
       18 . The method of preparing corrosion resistant compacted articles of  claim 15  wherein the ferrite factor of the metallurgical powder composition is from about 6 to about 20 and ferrite factor (K m ) is defined by the formula:  
         K   m =(weight percent Cr)−40(weight percent C+weight percent N)+4(weight percent Mo)−5(weight percent Cu)−4(weight percent Ni)−20(weight percent P)+6(weight percent Si)−2(weight percent Mn)+8(weight percent Ti)+2(weight percent Al).  
   
   
       19 . The method of preparing corrosion resistant compacted articles of  claim 15  wherein the iron based powder is a water-atomization powder.  
   
   
       20 . The method of preparing corrosion resistant compacted articles of  claim 15  further comprising the step of sintering the compacted article to form a dual phase microstructure of martensite and ferrite.  
   
   
       21 . The method of preparing corrosion resistant compacted articles of  claim 15  wherein the compacted article exhibits a density of greater than about 6.6 g/cm 3 .  
   
   
       22 . The method of preparing corrosion resistant compacted articles of  claim 20  wherein the sintered compact comprises from about 1.0 to about 20.0 volume percent of ferrite in a martensite matrix.  
   
   
       23 . The method of preparing corrosion resistant compacted articles of  claim 20  wherein the sintered compact exhibits a sintered density of from about 7.15 g/cm 3  to about 7.38 g/cm 3 .  
   
   
       24 . A stainless steel metallurgical powder composition comprising: 
 as a major component, an iron-based powder    as a minor component, alloy additives comprising chromium, molybdenum, nickel, silicon, manganese, copper, sulfur, phosphorus, titanium, and combinations thereof, wherein the stainless steel metallurgical powder composition achieves a dual phase microstructure in the as-sintered condition.    
   
   
       25 . The stainless steel metallurgical powder composition of  claim 24  wherein the dual phases are martensite and ferrite.  
   
   
       26 . The stainless steel metallurgical powder composition of  claim 24  wherein the alloy additives comprise: 
 about 0.01 to about 0.10 weight percent carbon,    about 8.0 to about 16.0 weight percent chromium,    about 0.1 to about 1.0 weight percent molybdenum,    about 0.01 to about 2.0 weight percent nickel,    about 0.01 to about 1.5 weight percent silicon,    about 0.01 to about 0.5 weight percent manganese,    about 0.01 to about 0.75 weight percent copper,    about 0.01 to about 0.10 weight percent sulfur,    about 0.01 to about 0.10 weight percent phosphorus,    about 0.01 to about 0.15 weight percent titanium, or    combinations thereof.    
   
   
       27 . The stainless steel metallurgical powder composition of  claim 24  wherein the ferrite factor is from 8 to 13 and ferrite factor (Km) is defined by the formula:  
         K   m =weight percent Cr+6*(weight percent Si)+8*(weight percent Ti)+4*(weight percent Mo)+2*(weight percent Al)−2*(weight percent Mn)−4*(weight percent Ni)−40*(weight percent C+weight percent N)−20*(weight percent P)−5*(weight percent Cu).  
   
   
       28 . The stainless steel metallurgical powder composition of  claim 24  wherein the ferrite factor is from 8 to 11.  
   
   
       29 . A sintered compact prepared from the stainless steel metallurgical powder composition of  claim 24  wherein the sintered compact comprises from about 2.0 to about 8.0 volume percent of ferrite in a martensite matrix.  
   
   
       30 . A sintered compact prepared from the stainless steel metallurgical powder composition of  claim 24  wherein the sintered compact exhibits a sintered density of from about 7.15 g/cm 3  to about 7.38 g/cm 3 .