Lubricant compositions for SI-AL alloy surfaces and methods for using

Abstract

A lubricant composition including: (A) greater than 50 wt % of a base stock based on the total weight of the composition selected from the group consisting of that of a Group III base oil, a Group IV base oil, and a combination thereof; and (B) one or more additional components. The one or more additional components are selected from the group consisting of: (i) one or more high or medium base carboxylate detergents; (ii) one or more low base carboxylate detergents, wherein the low base carboxylate detergent is present at a level of 0.60 wt % or less based on the total weight of the composition; (iii) one or more low base carboxylate detergents and one or more aromatics-containing base stock(s); and (iv) one or more phenolic detergents.

What is claimed is: 
     
         1 . A lubricant composition, comprising:
 (A) 50 wt % or more of a base stock, based on the total weight of the composition, selected from the group consisting of a Group III base oil, a Group IV base oil, and a combination thereof and   (B) one or more additional components selected from the group consisting of
 (i) one or more high or medium base carboxylate detergents; 
 (ii) one or more low base carboxylate detergents, wherein the one or more low base carboxylate detergents is present at a level of 0.60 wt % or less, based on the total weight of the composition; 
 (iii) one or more low base carboxylate detergents and one or more aromatics-containing base stock(s), wherein A is less than or equal to 190, wherein A is determined according to the formula 
   
       
         
           
             
               A 
               = 
               
                 
                   wt 
                    
                   
                       
                   
                    
                   % 
                    
                   
                       
                   
                    
                   low 
                    
                   
                       
                   
                    
                   base 
                    
                   
                       
                   
                    
                   carboxylate 
                    
                   
                       
                   
                    
                   detergent 
                 
                 
                   % 
                    
                   
                       
                   
                    
                   base 
                    
                   
                       
                   
                    
                   oil 
                    
                   
                       
                   
                    
                   proton 
                    
                   
                       
                   
                    
                   aromaticity 
                 
               
             
           
         
         
            wherein wt % low base carboxylate detergent is determined by the weight based on the total weight of the composition, and wherein % base oil proton aromaticity is the percentage of aromatics present in the base oil; and 
           (iv) one or more phenolic detergents, wherein if the one or more phenolic detergents is one or more phenate detergents, the one or more phenate detergent is present at a level of less than 5 wt % based on the total weight of the lubricant composition, 
         
         wherein the lubricant composition exhibits a frictional coefficient of less than or equal to 0.31 in an SRV Screener Test. 
       
     
     
         2 . The composition of  claim 1 , wherein the base stock is present at 60 wt % or more based on the total weight of the composition. 
     
     
         3 . The composition of  claim 1 , wherein the base stock is present at 70 wt % or more based on the total weight of the composition. 
     
     
         4 . The composition of  claim 1 , wherein the one or more low base carboxylate detergents is selected from a group comprising alkylated mono-carboxylates, wherein the carboxylate functional group may include a carboxylic acid, an ester, an amide, an imide, an anhydride, a halide, or a salt. 
     
     
         5 . The composition of  claim 1 , wherein the one or more low base carboxylate detergents is an alkylated salicylate detergent. 
     
     
         6 . The composition of  claim 1 , wherein the one or more low base carboxylate detergents is an alkylated calcium salicylate detergent. 
     
     
         7 . The composition of  claim 1 , wherein the one or more phenolic detergents is a phenate detergent. 
     
     
         8 . The composition of  claim 7 , wherein the phenolic detergent is a calcium phenate detergent. 
     
     
         9 . The composition of  claim 1 , wherein the low base carboxylate detergent has a TBN of less than 70. 
     
     
         10 . The composition of  claim 1 , wherein the base stock is a combination of a Group III base oil and a Group IV base oil. 
     
     
         11 . The composition of  claim 1 , wherein the aromatics-containing base stock is a Group II base stock. 
     
     
         12 . The composition of  claim 1 , wherein the one or more aromatics containing base stock is a Group V base stock. 
     
     
         14 . A method for lubricating a surface of a Si—Al alloy, comprising applying to the surface the lubricant composition of  claim 1 . 
     
     
         13 . A method of lubricating a cylinder liner of a composite of silicon microparticles in a silicon-aluminum alloy matrix and a nitrided steel piston ring, comprising applying to rubbing surfaces of the liner and the piston ring the lubricant composition of  claim 1 . 
     
     
         14 . A method of lubricating rubbing surfaces of dissimilar metallic materials in which one rubbing surface has a higher Vickers hardness than the other rubbing surface, comprising applying to the rubbing surfaces the lubricant composition of  claim 1 . 
     
     
         15 . The method of  claim 14 , wherein the one of the metallic materials is a ferrous alloy and the other of the metallic materials is a non-ferrous alloy.