Patent Publication Number: US-2017369973-A1

Title: Corrosion resistant cemented carbide for fluid handling

Description:
TECHNICAL FIELD/INDUSTRIAL APPLICABILITY 
     The present disclosure relates to cemented carbides for flow components, and more particularly to fluid handling components such as seal rings having improved service life. 
     BACKGROUND 
     Seal rings are the key critical component in mechanical shaft seals for pumps where corrosion resistance is an issue. Cemented carbides show a good mechanical performance in this kind of application. 
     Similarly, cemented carbide flow components, the primary function of which is to control the pressure and flow of well products, are used in, for example, the oil and gas industry where components are subjected to high pressures of multi-media fluid where there is a corrosive environment. A cemented carbide grade with Ni—Cr—Mo binder having improved corrosion resistance for use in choke valves is disclosed in WO2012/045815, also assigned to the assignee of the present disclosure 
     One of the most important properties for seal rings is thermal conductivity. This is crucial for seal rings because during the operation of a pump the friction between the seal rings generates heat. This heat needs to be conducted away; otherwise the heat will lead to a temperature increase in the sealing gap, which again can lead to evaporation of the lubricating film and dry running. Point temperatures of over 300° C. can be reached during seal ring dry running. Thus, the thermal conductivity of the seal ring material is vitally important in dissipating the temperature generated. Materials with low thermal conductivities tend to fail prematurely in service due to thermal cracking. Therefore, there is still a need for a type or grade of cemented carbide having high thermal conductivity and high corrosion resistance. 
     SUMMARY 
     It is an aspect of the present disclosure to provide a cemented carbide for fluid handling components and for a seal ring, all of which having improved corrosion resistance. 
     The present disclosure therefore provides a cemented carbide composition for fluid handling components and/or seal rings comprises in wt % about balance WC; about 7-11 Ni; about 0.5 to 2.5 Cr 3 C 2 ; and about 0.5 to about 2.5 Mo. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter further comprises of from 0.3 to 1.5 wt % Nb. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 8.0 to about 10.1 wt % Ni. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 8.0 to about 9.0 wt % Ni, such as 8.49 wt % 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 9.1 to about 10.1 wt % Ni, such as 9.6 wt % 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 0.7 to about 1.0wt % Cr 3 C 2 . 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 0.7 to about 0.9 wt % Cr 3 C 2 , such as 0.8 wt % 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 0.8 to about 1.0 wt % Cr 3 C 2 , such as 0.9 wt %. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 0.7 to about 1.0wt % Mo. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 0.7 to about 0.9 wt % Mo, such as 0.8 wt %. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 0.8 to about 1.0 wt % Mo, such as 0.9 wt %. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 88.0 to about 90.6 wt % WC. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 87.9 to about 89.1 wt % WC, such as 88.6 wt %. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 89.4 to about 90.5 wt % WC, such as 89.91 wt % 
     In an embodiment, the composition as defined hereinabove or hereinafter has an average grain size of from about 4 μm to about 10 μm, such as 8 μm. 
     In an embodiment, a cemented carbide for a fluid handling component or seal ring as defined hereinabove or hereinafter, has a composition comprising in wt %: of 89.91% WC; of 8.49 Ni; of 0.8 Cr 3 C 2 ; and of 0.8 Mo, wherein the composition has an average grain size equal to or greater than 4 μm. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition has a density of about 14.3 to about 14.7 g/cm 3 , such as about 14.4 to about 14.6 g/cm 3 . 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a density of from 14.4 to 14.6 g/cm3. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a hardness of from 1000 to 1100 HV30. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a toughness of from 10 to 13 MPa·√m. 
     In an embodiment, a cemented carbide for a fluid handling component or seal ring as defined hereinabove or hereinafter, the cemented carbide having a composition comprising in wt % of 88.6% WC; of 9.6 Ni; of 0.9 Cr 3 C 2 ; and of 0.9 Mo, wherein the composition has an average WC grain size greater than 4 μm. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has an average WC grain size of 8 μm. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a hardness of about 990 HV30. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a toughness of about 12.2 MPa·√m. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a density of 14.4 g/cm 3 . 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has an average WC grain size of 4 μm. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a hardness of 1290 HV30. 
     In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a toughness of about 11.6 MPa·√m. 
     The foregoing summary, as well as the following detailed description of the embodiments, will be better understood when read in conjunction with the appended drawings. It should be understood that the embodiments depicted are not limited to the precise arrangements and instrumentalities shown. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an SEM image of an embodiment of cemented carbide for a flow component or seal ring. 
         FIG. 2  is an SEM image of another embodiment of cemented carbide for a flow component or a seal ring. 
         FIG. 3  is an SEM image of another embodiment of cemented carbide for a flow component or a seal ring. 
         FIG. 4  is an SEM image of another embodiment of cemented carbide for a flow component or a seal ring. 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, the term “about” means plus or minus 10% of the numerical value of the number with which it is being used. Therefore, about 50% means in the range of 45%-55%. 
     As will be described fully herein, embodiments of the present disclosure relate to cemented carbides for flow components (herein, the term “component” means parts or pieces), particularly for seal rings used in the oil and gas industry, where the components are subjected to high pressures of multi-media fluid and where there is a corrosive environment. Under severe conditions of multi flow media; these components may suffer from extreme mass loss by exposure to solid particle erosion, acidic corrosion erosion-corrosion synergy and cavitation mechanisms even when fitted with cemented carbide trims. 
     Seal rings are the key critical component in mechanical shaft seals for pumps. The seal rings act as barriers in pumps (i.e., to separate liquids and confine pressure) by preventing leakage and excluding contamination. Cemented carbide shows a good mechanical performance in this kind of application. 
     The cemented carbide seal rings of the present disclosure have improved application relevant properties, such as improved corrosion resistance. The carbon content within the sintered cemented carbide should be kept within a narrow range in order to retain a high resistance to corrosion and wear, as well as have a high toughness. The carbon level of the sintered structure is held in the lower portion of the range between free carbon in the microstructure (top limit) and eta-phase initiation (bottom limit). 
     Conventional powder metallurgical methods, such as (but not limited to) milling, drying, pressing, shaping, sintering and sinter hipping, which are used for manufacture of conventional cemented carbides are used to manufacture embodiments of the present disclosure. 
     A cemented carbide for seal rings (CR) according to an embodiment the present disclosure has a composition in weight percent % of about balance WC; 7-11 Ni; 0.5-2.5 Cr 3 C 2 ; and Mo of about 0.5 to about 2.5. 
     It should be appreciated that the following examples are illustrative, non-limiting examples. The compositions and results of the embodiments are shown in Tables 1 and 2 below. 
     EXAMPLES 
       
     
       
         
           
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Ref 
               
            
           
           
               
               
               
               
            
               
                   
                 A 
                 B 
                 C 
               
            
           
           
               
               
            
               
                   
                 Sample 
               
            
           
           
               
               
               
               
            
               
                   
                 CR seal ring 
                 CR seal ring 
                 CR seal ring 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                 WC 
                 88.6 
                 88.6 
                 89.91 
               
               
                 WC grain size (μm) 
                 4 
                 8 
                 8 
               
               
                 TiC (wt %) 
                 0 
                 0 
                 0 
               
               
                 Co (wt %) 
                 0 
                 0 
                 0 
               
               
                 Ni (wt %) 
                 9.6 
                 9.6 
                 8.49 
               
               
                 Mo (wt %) 
                 0.9 
                 0.9 
                 0.8 
               
               
                 Cr 3 C 2  (wt %) 
                 0.9 
                 0.9 
                 0.8 
               
               
                   
               
            
           
         
       
     
                             TABLE 2                          Ref                                 A   B   C                         Sample                                         CR seal           CR seal ring   CR seal ring   ring                                                 Density (gm/cm 3 )   14.4   14.4   14.4-14.6           Hardness (Hv30)   1290   990   1000-1100           Toughness (K1c)   11.6   12.2   10.0-13.0                        
In the examples below the powders were sourced from the following suppliers: (W,Ti)C from Zhuzhou or HC Starck, Co from Umicore or Freeport, Ni from Inco, Mo from HC Starck and Cr 3 C 2  from Zhuzhou or HC Starck
 
     Example 1 
     A cemented carbide grade with the composition in wt-% of about 88.6 WC; about 0.9 Cr 3 C 2 ; about 0.9 Mo; and about 9.6 Ni was producing using WC powder with an average FSSS (Fisher Sub Sieve Sizer) particle size (d50) of greater than about 0.5 μm, for example, about 4 to about 8. The cemented carbide samples were prepared from powders forming the hard constituents and powders forming the binder. The powders were wet milled together with lubricant and anti-flocculating agent until a homogeneous mixture was obtained and granulated by drying. The dried powder was pressed on the Tox press to bodies and ‘green machined’ before sintering. Sintering was performed at 1360-1410° C. for about 1 hour in vacuum, followed by applying a high pressure, 50 bar Argon, at sintering temperature for about 30 minutes to obtain a dense structure before cooling. The sintered structure is shown in  FIG. 1  with a grain size of 0.8 μm. 
     Referring to Table 2, with WC grain size of about 4 μm has a hardness HV30 of about 1290 and a toughness of K1C 11.6 MPa·√m. With WC grain size of about 8 μm the harness HV30 is about 990 and the toughness K1C IS 12.2 MPa·√m. It can be observed that when the coarser raw material is used (4 or 8 μm) the hardness is reduced and the toughness increased.  FIG. 2  is an SEM image of the sintered structure with a grain size of 4 μm.  FIG. 3  is an SEM image of the sintered structure with a grain size of 8 μm. 
     Example 2 
     A cemented carbide grade with the compositions in wt-% of about 89.91 WC; about 0.8 Cr 3 C 2 ; about 0.8 Mo; and about 8.49 Ni and was produced using WC powder with an average FSSS particle size (d 50 ) of greater than about about 4 μm and/or about 8 μm. The cemented carbide samples were prepared from powders forming the hard constituents and powders forming the binder. The powders were wet milled together with lubricant and anti-flocculating agent until a homogeneous mixture was obtained and granulated by drying. The dried powder was pressed on the Tox press to bodies and ‘green machined’ before sintering. Sintering was performed at 1360-1410° C. for about 1 hour in vacuum, followed by applying a high pressure, 50 bar Argon, at sintering temperature for about 30 minutes to obtain a dense structure before cooling. The sintered structure with a grain size of 8 μm is shown in  FIG. 4 . 
     The composition mentioned has the following properties: density: 14.4-14.6 g/cm3; hardness HV30: 1000-1100 and toughness K1C: 10-13 MPa·√m. The grades disclosed herein demonstrate improved corrosion resistance in comparison to a standard seal ring grade. Corrosion resistance was determined using a modified test to ASTM G61. ASTM G61 covers a procedure for conducting potential dynamic polarization measurements. The modification of this standard has been in the media used. Instead of using 3.5% NaCl solution in the tests, artificial seawater according to ASTM D1141 was used as the media. Furthermore, the flushed port cell used in ASTM G61 was replaced by sealing the specimen with epoxy to avoid crevice corrosion on the edge of the sample. The pitting potential was used as a measure for comparison. The higher the value, the better is the corrosion resistance of the material. The value measured for a standard seal ring grade was Epit=263 mV SCE. However, for the above CR grade the Epit=443 mV SCE showing improved corrosion resistance. 
     As discussed supra, one of the key properties for seal rings is thermal conductivity. One way to increase thermal conductivity is to increase the average WC grain size. Thermal conductivity was measured between a cemented carbide grade of 88.6% WC, 9.6% Nicke1,0.9% Cr 3 C 2  and 0.9% Mo having an average WC grain size of 0.8 μm. As shown in Table 3 below, the higher the grain size the higher the thermal conductivity. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
             
            
               
                   
                   
               
               
                   
                 Thermal conductivity (W/(mK)) 
                   
               
            
           
           
               
               
               
            
               
                 Temperature (° C.) 
                 Choke valve grade 
                 A 
               
               
                   
               
               
                 Room temperature 
                 46 
                 85 
               
               
                 200 
                 53 
                 80 
               
               
                 401 
                 53 
                 72 
               
               
                 1000 
                 55 
                 62 
               
               
                   
               
            
           
         
       
     
     Itemized List of Embodiments 
     1. A cemented carbide for a fluid handling component or seal ring, the cemented carbide having a composition comprising in wt %:
         a balance of WC;   of 7-11 Ni;   of 0.5-2.5 Cr 3 C 2 ; and   of 0.5-2.5 Mo,   wherein the composition has an average WC grain size greater than 4 μm.       

     2. The cemented carbide of item 1, wherein the composition further comprises of from 0.3 to 1.5 wt % Nb. 
     3. The cemented carbide of items 1 or 2, wherein the composition has an average grain size of 8 μm. 
     4. A cemented carbide for a fluid handling component or seal ring, the cemented carbide having a composition comprising in wt %:
         of 89.91% WC;   of 8.49 Ni;   of 0.8 Cr 3 C 2 ; and   of 0.8 Mo,   wherein the composition has an average grain size greater than 4 μm.       

     5. The cemented carbide of item 4, wherein the composition has an average grain size of 8 μm. 
     6. The cemented carbide of item 4 or 5, wherein the composition has a density of from 14.4 to 14.6 g/cm 3 . 
     7. The cemented carbide of any of items 4-6, wherein the composition has a hardness of from 1000 to 1100 HV30. 
     8. The cemented carbide of any of items 4-7, wherein the composition has a toughness of from 10 to 13 MPa·√m. 
     9. A cemented carbide for a fluid handling component or seal ring, the cemented carbide having a composition comprising in wt %:
         of 88.6% WC;   of 9.6 Ni;   of 0.9 Cr 3 C 2 ; and   of 0.9 Mo,   wherein the composition has an average WC grain size greater than 4 μm.       

     10. The cemented carbide of item 9, wherein the composition has an average WC grain size of 8 μm. 
     11. The cemented carbide of items 9 or 10, wherein the composition has a hardness of from 990 HV30. 
     12. The cemented carbide of any of items 9-11, wherein the composition has a toughness of from 12.2 MPa·√m. 
     13. The cemented carbide of any of items 9-12, wherein the composition has a density of from 14.4 g/cm 3 . 
     14. The cemented carbide of item 9, wherein the composition has an average WC grain size of 4 μm. 
     15. The cemented carbide of item 9 or 14, wherein the composition has a hardness of from 1290 HV30. 
     16. The cemented carbide of any of items 9, 14 or 15, wherein the composition has a toughness of about 11.6 MPa·√m. 
     Although the present embodiments have been described in relation to particular aspects thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred therefore, that the present embodiment(s) be limited not by the specific disclosure herein, but only by the appended claims.