Protecting an element from excessive surface wear by localized hardening

Abstract

A method of protecting an element from excessive surface wear is provided. In this method, a localized area of the element that will be subjected to excessive surface wear is exposed to induction heating for a period sufficient to heat the localized area to an elevated temperature at which the localized area undergoes austenitic transformation. The localized area is quenched, followed by tempering, and then cooling. A result of the method is a localized hardened area formed monolithically with the element and having a localized hardness that is greater than a base hardness of the element.

1 . A method of protecting an element from excessive surface wear, comprising:
 exposing a localized area of the element that will be subjected to the excessive surface wear to induction heating for a period sufficient to heat the localized area to an elevated temperature at which the localized area undergoes austenitic transformation;   quenching the localized area;   tempering the localized area; and   cooling the localized area;   wherein a result of the method is a localized hardened area formed monolithically with the element and having a localized hardness that is greater than a base hardness of the element.   
   
   
       2 . The method of  claim 1 , wherein the induction heating is at a frequency in a range from 1 kHz to 10 kHz and a power density of 0.5 kW/in 2  to 10 kW/in 2 . 
   
   
       3 . The method of  claim 1 , wherein the element is made of low-alloy steel. 
   
   
       4 . The method of  claim 1 , wherein a depth of the localized hardened area is at least 0.25 in. (0.635 cm). 
   
   
       5 . The method of  claim 1 , wherein the tempering step occurs at a temperature in a range from 250° F. to 295° F. 
   
   
       6 . The method of  claim 1 , wherein the localized hardness, expressed as Rockwell hardness, is in a range from 56 to 63 HRC. 
   
   
       7 . The method of  claim 6 , wherein the base hardness, expressed as Rockwell hardness, is in a range from 30 to 36 HRC. 
   
   
       8 . The method of  claim 1 , wherein the localized hardness is at least 40% greater than the base hardness. 
   
   
       9 . The method of  claim 1 , wherein quenching is in an aqueous polymer medium. 
   
   
       10 . The method of  claim 9 , wherein the aqueous polymer medium comprises a polymer selected from polyalkylene glycol and polyethylene glycol. 
   
   
       11 . A downhole tool protected from excessive surface wear, comprising:
 a tool body made of a material having a base hardness; and   a localized hardened area formed monolithically with the tool body, the localized hardened area having a localized hardness that is greater than the base hardness.   
   
   
       12 . The downhole tool of  claim 11 , wherein the localized hardness, expressed as Rockwell hardness, is in a range from 56 to 63 HRC. 
   
   
       13 . The downhole tool of  claim 11 , wherein the base hardness, expressed as Rockwell hardness, is in a range from 30 to 36 HRC. 
   
   
       14 . The downhole tool of  claim 11 , wherein the localized hardness is at least 40% greater than the base hardness. 
   
   
       15 . The downhole tool of  claim 11 , wherein the material of the tool body is comprised of a low-alloy steel. 
   
   
       16 . The downhole tool of  claim 11 , wherein a depth of the localized hardened area is at least 0.25 in. (0.635 cm).