Wear-resistant, corrosion-resistant cobalt-based alloys

Abstract

A Co-based alloy comprising 13-16 wt % Cr, 20-30 wt % Mo, 2.2-3.2 wt % Si, and balance Co, with a Cr:Si ratio of between about 4.5 and about 7.5, a Mo:Si ratio of between about 9 and about 15, wear resistance, and corrosion resistance in both oxidizing and reducing acids.

What is claimed is:  
     
         1 . A Co-based alloy comprising: 
 13-16 wt % Cr,    20-30 wt % Mo,    2.2-3.2 wt % Si, and    balance Co;    the alloy having a Cr:Si ratio of between about 4.5 and about 7.5, a Mo:Si ratio of between about 9 and about 15, wear resistance, and corrosion resistance in both oxidizing and reducing acids.    
     
     
         2 . The alloy of  claim 1  consisting essentially of 
 13-16 wt % Cr,  
 20-30 wt % Mo,  
 2.2-3.2 wt % Si, and  
 48-62 wt % Co.  
 
     
     
         3 . The alloy of  claim 1  having corrosion resistance in reducing acid H 2 SO 4  characterized by less than about 50 mm/year weight loss when tested according to ASTM specification G31-72 in a 10% solution at 102 C.  
     
     
         4 . The alloy of  claim 1  having corrosion resistance in oxidizing acid HNO 3  characterized by less than about 300 mm/year weight loss when tested according to ASTM specification G31-72 in a 65% solution at 66 C.  
     
     
         5 . The alloy of  claim 1  having corrosion resistance in reducing acid HCl characterized by less than about 4 mm/year weight loss when tested according to ASTM specification G31-72 in a 5% solution at 66 C.  
     
     
         6 . The alloy of  claim 1  having impact strength of at least about 2.0 Joules when evaluated by an un-notched Charpy impact test according to ASTM specification E23-96.  
     
     
         7 . The alloy of  claim 1  having a metal-to-metal wear resistance characterized by a volume loss of less than about 0.06 cubic millimeters when tested according to ASTM G133-95 at 482 C with alloy cylinders in metal-to-metal wear contact with nitrided 310 stainless steel flat plates.  
     
     
         8 . The alloy of  claim 2  having corrosion resistance in reducing acid H 2 SO 4  characterized by less than about 50 mm/year weight loss when tested according to ASTM specification G31-72 in a 10% solution at 102 C.  
     
     
         9 . The alloy of  claim 2  having corrosion resistance in oxidizing acid HNO 3  characterized by less than about 300 mm/year weight loss when tested according to ASTM specification G31-72 in a 65% solution at 66 C.  
     
     
         10 . The alloy of  claim 2  having corrosion resistance in reducing acid HCl characterized by less than about 4 mm/year weight loss when tested according to ASTM specification G31-72 in a 5% solution at 66 C.  
     
     
         11 . The alloy of  claim 2  having impact strength of at least about 2.0 Joules when evaluated by an un-notched Charpy impact test according to ASTM specification E23-96.  
     
     
         12 . The alloy of  claim 1  comprising about 14 wt % Cr.  
     
     
         13 . The alloy of  claim 1  comprising about 26 wt % Mo.  
     
     
         14 . The alloy of  claim 1  comprising about 2.6 wt % Si.  
     
     
         15 . The alloy of  claim 1  having a Cr:Si ratio of about 5.4.  
     
     
         16 . The alloy of  claim 1  having a Mo:Si ratio of about 10.8.  
     
     
         17 . The alloy of  claim 1  consisting essentially of 
 13-16 wt % Cr,  
 20-30 wt % Mo,  
 2.2-3.2 wt % Si, and  
 48-62 wt % Co;  
 wherein the alloy is Mn-free, Cu-free, and free of all alloying elements having a material effect on metallurgical properties other than Cr, Mo, and Si; and  
 wherein the alloy has a total trace element content of no more than 2 wt %.  
 
     
     
         18 . The alloy of  claim 1  consisting essentially of 
 13-16 wt % Cr,  
 20-30 wt % Mo,  
 2.2-3.2 wt % Si, and  
 48-62 wt % Co;  
 wherein the alloy is Mn-free, Cu-free, and free of all alloying elements having a material effect on metallurgical properties other than Cr, Mo, and Si;  
 wherein the alloy has a total trace element content of no more than 2 wt %;  
 wherein the alloy has a Cr:Si ratio of between 4.5 and 7.5 and a Mo:Si ratio between 9 and 15.  
 
     
     
         19 . The alloy of  claim 18  having corrosion resistance in reducing acid H 2 SO 4  characterized by less than about 50 mm/year weight loss when tested according to ASTM specification G31-72 in a 10% solution at 102 C.  
     
     
         20 . The alloy of  claim 18  having corrosion resistance in oxidizing acid HNO 3  characterized by less than about 300 mm/year weight loss when tested according to ASTM specification G31-72 in a 65% solution at 66 C.  
     
     
         21 . The alloy of  claim 18  having corrosion resistance in reducing acid HCl characterized by less than about 4 mm/year weight loss when tested according to ASTM specification G31-72 in a 5% solution at 66 C.  
     
     
         22 . The alloy of  claim 18  having impact strength of at least about 2.0 Joules when evaluated by an un-notched Charpy impact test according to ASTM specification E23-96.  
     
     
         23 . The alloy of  claim 1  having a microstructure of about 40-55% by volume Laves phase.  
     
     
         24 . The alloy of  claim 1  having a microstructure of about 40-55% by volume Laves phase and a Laves phase Cr:Si ratio between about 1.04 and about 1.36.  
     
     
         25 . A Co-based alloy consisting essentially of: 
 13-16 wt % Cr,    20-30 wt % Mo,    2.2-3.2 wt % Si, and    48-62 wt % Co;    wherein the alloy is Mn-free, Cu-free, and free of all alloying elements having a material effect on metallurgical properties other than Cr, Mo, and Si;    wherein the alloy has a total trace element content of no more than 2 wt %;    wherein the alloy has a Cr:Si ratio of between 4.5 and 7.5 and a Mo:Si ratio between 9 and 15;    wherein the alloy demonstrates corrosion resistance in reducing acid H 2 SO 4  characterized by less than about 50 mm/year weight loss when tested according to ASTM specification G31-72 in a 10% solution at 102 C, corrosion resistance in oxidizing acid HNO 3  characterized by less than about 300 mm/year weight loss when tested according to ASTM specification G31-72 in a 65% solution at 66 C, and corrosion resistance in reducing acid HCl characterized by less than about 4 mm/year weight loss when tested according to ASTM specification G31-72 in a 5% solution at 66 C.    
     
     
         26 . The alloy of  claim 25  having impact strength of at least about 2.0 Joules when evaluated by an un-notched Charpy impact test according to ASTM specification E23-96.  
     
     
         27 . The alloy of  claim 25  having a microstructure having about 40-55% by volume Laves phase.  
     
     
         28 . A Co-based alloy consisting essentially of, by approximate wt %: 
 14 Cr,    26 Mo,    2.6 Si, and    48-62 wt % Co;    wherein the alloy is Mn-free, Cu-free, and free of all alloying elements having a material effect on metallurgical properties other than Cr, Mo, and Si; and    wherein the alloy has a total trace element content of no more than 2 wt %.    
     
     
         29 . The alloy of  claim 28  wherein the alloy demonstrates corrosion resistance in reducing acid H 2 SO 4  characterized by less than about 50 mm/year weight loss when tested according to ASTM specification G31-72 in a 10% solution at 102 C.  
     
     
         30 . The alloy of  claim 28  wherein the alloy demonstrates corrosion resistance in oxidizing acid HNO 3  characterized by less than about 300 mm/year weight loss when tested according to ASTM specification G31-72 in a 65% solution at 66 C.  
     
     
         31 . The alloy of  claim 28  wherein the alloy demonstrates corrosion resistance in reducing acid HCl characterized by less than about 4 mm/year weight loss when tested according to ASTM specification G31-72 in a 5% solution at 66 C.  
     
     
         32 . The alloy of  claim 28  wherein the alloy demonstrates corrosion resistance in reducing acid H 2 SO 4  characterized by less than about 50 mm/year weight loss when tested according to ASTM specification G31-72 in a 10% solution at 102 C, corrosion resistance in oxidizing acid HNO 3  characterized by less than about 300 mm/year weight loss when tested according to ASTM specification G31-72 in a 65% solution at 66 C, and corrosion resistance in reducing acid HCl characterized by less than about 4 mm/year weight loss when tested according to ASTM specification G31-72 in a 5% solution at 66 C.  
     
     
         33 . The alloy of  claim 28  having impact strength of at least about 2.0 Joules when evaluated by an un-notched Charpy impact test according to ASTM specification E23-96.  
     
     
         34 . A Co-based alloy consisting essentially of: 
 13-16 wt % Cr,    20-30 wt % Mo,    2.2-3.2 wt % Si, and    48-62 wt % Co;    wherein the alloy is Mn-free; Cu-free; free of all alloying elements having a material effect on metallurgical properties other than Cr, Mo, and Si; and has a total trace element content of no more than about 2 wt %;    wherein the alloy has a Cr:Si ratio of between 4.5 and 7.5 and a Mo:Si ratio between 9 and 15;    wherein the alloy demonstrates corrosion resistance in reducing acid H 2 SO 4  characterized by less than about 50 mm/year weight loss when tested according to ASTM specification G31-72 in a 10% solution at 102 C, corrosion resistance in oxidizing acid HNO 3  characterized by less than about 300 mm/year weight loss when tested according to ASTM specification G31-72 in a 65% solution at 66 C, corrosion resistance in reducing acid HCl characterized by less than about 4 mm/year weight loss when tested according to ASTM specification G31-72 in a 5% solution at 66 C, and impact strength of at least about 2.0 Joules when evaluated by an un-notched Charpy impact test according to ASTM specification E23-96; and    wherein the alloy has a microstructure comprising about 40-55% by volume Laves phase.