Ultra-fast boriding of metal surfaces for improved properties

Abstract

A method of ultra-fast boriding of a metal surface. The method includes the step of providing a metal component, providing a molten electrolyte having boron components therein, providing an electrochemical boriding system including an induction furnace, operating the induction furnace to establish a high temperature for the molten electrolyte, and boriding the metal surface to achieve a boride layer on the metal surface.

1 . A method of boriding a surface of a metal comprising:
 providing a metal component;   providing a molten electrolyte having boron components therein;   providing an electrochemical boriding system including one of an induction furnace and a resistively-heated furnace;   providing a current to the metal component;   operating the furnace to establish a high temperature for the molten electrolyte; and   boriding the metal surface to achieve a boride layer on the metal surface,   wherein a boriding rate of at least about 2 μm/minute of the metal component is achieved for a boriding period of less than about 30 minutes.   
   
   
       2 . The method as defined in  claim 1 , wherein the boron components comprise a borax. 
   
   
       3 . The method as defined in  claim 1 , wherein the molten electrolyte further includes an additive selected from the group consisting of inorganic sodium, potassium, and lithium compounds. 
   
   
       4 . The method as defined in  claim 2 , wherein the borax ranges from about 30 to about 95 weight percent. 
   
   
       5 . The method as defined in  claim 4 , further including sodium carbonate ranging between about 5-70 weight percent. 
   
   
       6 . The method as defined in  claim 2 , further including an additive selected from the group consisting of an alkaline halide and an alkaline earth halide. 
   
   
       7 . The method as defined in  claim 6 , wherein the additive consists essentially of at least one of CaCl 2  and NaCl. 
   
   
       8 . The method as defined in  claim 7 , wherein the additive ranges from about 0.1-25 weight percent. 
   
   
       9 . The method as defined in  claim 7 , wherein a ratio of Na 2 O/B 2 O 3  is controlled in the molten electrolyte to reduce at least one of Na +  and Ca ++  ions present on the metal surface. 
   
   
       10 . The method as defined in  claim 9 , wherein the boron concentration in the molten electrolyte is further increased to accelerate diffusion of boron ions, thereby accelerating boride layer growth on the metal surface. 
   
   
       11 . The method as defined in  claim 1 , wherein the electrochemical boriding system includes an anode and cathode and a separation distance between the anode and cathode is adjusted to accelerate the rate of forming a boride on the metal surface. 
   
   
       12 . The method as defined in  claim 1 , further including the step of agitating the electrolyte to increase the rate of boriding the metal surface. 
   
   
       13 . The method as defined in  claim 1 , wherein the metal component comprises a steel and the method further includes the step of quenching the metal from the molten electrolyte, thereby forming martensitic phases along with the boride layer proximate the metal surface. 
   
   
       14 . A method of boriding a surface of a metal comprising:
 providing a metal component comprising a transition metal electrically coupled to a cathode;   providing a molten electrolyte having boron components comprising about 30 to about 95 weight percent borax therein;   providing one or more additives to the molten electrolyte to modify at least one of the electrochemical properties of the molten electrolyte, the viscosity of the molten electrolyte, and the melting temperature of the electrolyte;   providing an electrochemical boriding system including one of an induction and a resistively-heated furnace;   providing an electrical charge to the metal component;   maintaining the molten electrolyte between about 700° C. and about 1000° C.; and   boriding the metal surface to achieve a boride layer on the metal surface.   
   
   
       15 . The method of  claim 14 , further including the step of agitating the electrolyte to enhance the boriding rate of the metal component. 
   
   
       16 . The method of  claim 14 , wherein at least one of the one or more additives is selected from the group consisting of an alkaline halide and an alkaline earth halide. 
   
   
       17 . The method of  claim 14 , further including the step of reversing the polarization of the charge to the metal component. 
   
   
       18 . A treated metal with a surface having a boride layer thereon formed by the process of:
 providing a metal component;   providing a molten electrolyte having boron components therein;   providing one or more additives to the molten electrolyte to modify at least one of the electrochemical properties of the molten electrolyte, the viscosity of the molten electrolyte, and the melting temperature of the electrolyte;   providing an electrochemical boriding system including one of an induction and a resistively heated furnace;   operating the furnace to establish a high temperature for the molten electrolyte; and   boriding the metal surface to achieve a boride layer on the metal surface,   wherein the surface of the boride layer has a hardness value of at least about ten times the hardness of the untreated metal component.   
   
   
       19 . The treated metal as defined in  claim 18 , further including a step of masking a portion of the metal component to selectively boride a portion of the metal component.