Erosion-corrosion resistant nitride cermets

Abstract

The invention includes a cermet composition represented by the formula (PQ)(RS) comprising: a ceramic phase (PQ) and a binder phase (RS) wherein, P is a metal selected from the group consisting of Si, Mn, Fe, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and mixtures thereof, Q is nitride, R is a metal selected from the group consisting of Fe, Ni, Co, Mn and mixtures thereof, S consists essentially of at least one element selected from Cr, Al, Si, and Y, and at least one reactive wetting aliovalent element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and mixtures thereof.

1 - 14 . (canceled)  
   
   
       15 . A method for protecting a metal surface subject to erosion at temperatures up to 1000° C., the method comprising providing the metal surface with a cermet composition represented by the formula (PQ)(RS) comprising: a ceramic phase (PQ) and a binder phase (RS) wherein, 
 P is a metal selected from the group consisting of Si, Mn, Fe, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and mixtures thereof,    Q is nitride,    R is a metal selected from the group consisting of Fe, Ni, Co, Mn and mixtures thereof,    S consists essentially of at least one element selected from Cr, Si, Y and mixtures thereof, and at least one reactive wetting aliovalent element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and mixtures thereof, wherein the combined weights of said Cr, Si, and Y and mixtures thereof is at least 12 wt % based on the weight of the binder phase (RS) and    wherein the ceramic phase (PQ) ranges from about 30 to 95 vol % based on the volume of the cermet.    
   
   
       16 . The method of  claim 15  wherein said surface is subjected to erosion at temperatures in the range of 300° C. to 1000° C.  
   
   
       17 . The method of  claim 15  wherein said surface comprises the inner surface of a fluid-solids separation cyclone.  
   
   
       18 - 30 . (canceled)  
   
   
       31 . The method of  claim 15  wherein the molar ratio of P:Q in the ceramic phase (PQ) can vary in the range of 1:3 to 3:1.  
   
   
       32 . The method of  claim 15  wherein (PQ) ranges from of about 55 to 95 vol % based on the volume of the cermet.  
   
   
       33 . The method of  claim 15  wherein said ceramic phase (PQ) is dispersed in the binder phase (RS) as spherical particles in the size range of 0.5 microns to 3000 microns diameter.  
   
   
       34 . The method of  claim 15  wherein the binder phase (RS) is in the range of 5 to 70 vol % based on the volume of the cermet and the mass ratio of R to S ranges from 50/50 to 90/10.  
   
   
       35 . The method of  claim 15  wherein said at least one reactive wetting aliovalent element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and mixtures thereof is in the range of 0.01 to 5 wt % based on the total weight of the binder phase (RS).  
   
   
       36 . The method of  claim 15  further comprising a secondary nitride (P′Q) wherein P′ is selected from the group consisting of Si, Mn, Fe, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ni, Co, Al, Y, and mixtures thereof.  
   
   
       37 . The method of  claim 15  having a fracture toughness of greater than about 3 MPa m 1/2 .  
   
   
       38 . The method of  claim 15  having an erosion rate less than about 1×10 −6  cc/gram loss when subject to 1200 g/min of 10 μm to 100 μm SiC particles in air with an impact velocity of at least about 45.7 m/sec (150 ft/sec) and at an impact angle of about 45 degrees and a temperature of at least about 732° C. (1350° F.) for at least 7 hours.  
   
   
       39 . The method of  claim 15  having corrosion rate less than about 1×10 −10  g 2 /cm 4 ·s or an average oxide scale of less than 150 μm thickness when subject to 100 cc/min air at 800° C. for at least 65 hours.  
   
   
       40 . The method of  claim 15  having an erosion rate less than about 1×10 −6  cc/gram when subject to 1200 g/min of 10 μm to 100 μm SiC particles in air with an impact velocity of at least about 45.7 m/sec (150 ft/sec) and at an impact angle of about 45 degrees and a temperature of at least about 732° C. (1350° F.) for at least 7 hours and a corrosion rate less than about 1×10 −10  g 2 /cm 4 ·s or an average oxide scale of less than 150 μm thickness when subject to 100 cc/min air at 800° C. for at least 65 hours.  
   
   
       41 . The method of  claim 15  having embrittling phases less than about 5 vol % based on the volume of the cermet.  
   
   
       42 . The method of  claim 15  wherein the overall thickness of the cermet composition is greater than 5 millimeters.