Hardfacing rock bit cones for erosion protection

Abstract

A roller cone for a rock bit is disclosed. The cone includes a cone substrate and hardfacing applied by a welding process in grooves on the exterior surface of the cone substrate. The cone also includes hardfacing applied by a thermal spraying process to insert lands on the exterior surface of the cone substrate.

What is claimed is:  
     
         1 . A roller cone for a rock bit, comprising: 
 a cone substrate;    hardfacing applied by a welding process in grooves on the exterior surface of the cone substrate; and    hardfacing applied by a thermal spraying process to insert lands on the exterior surface of the cone substrate.    
     
     
         2 . The roller cone as defined in    claim 1    wherein the welding process comprises plasma transferred arc welding.  
     
     
         3 . The roller cone as defined in    claim 1    wherein the thermal spraying process comprises at least one of HVOF, HAOF and D-gun spraying.  
     
     
         4 . The roller cone as defined in    claim 1    wherein the hardfacing applied by at least one of the welding process and thermal spraying process comprises tungsten carbide.  
     
     
         5 . A roller cone bit, comprising: 
 a bit body adapted to be coupled to have a drill string and having at least one journal depending therefrom;    a roller cone rotatably mounted on the at least one journal, the roller cone comprising a cone substrate, hardfacing applied by a welding process in grooves on the exterior surface of the cone substrate and hardfacing applied by a thermal spraying process to insert lands on the exterior surface of the cone substrate; and    cutting elements affixed to the roller cone at selected positions thereon.    
     
     
         6 . The roller cone bit as defined in    claim 5    wherein the welding process comprises plasma transferred arc welding.  
     
     
         7 . The roller cone bit as defined in    claim 5    wherein the thermal spraying process comprises at least one of HVOF, HAOF and D-gun spraying.  
     
     
         8 . The roller cone bit as defined in    claim 5    wherein the hardfacing applied by at least one of the welding process and thermal spraying process comprises tungsten carbide.  
     
     
         9 . A method for hardfacing a roller cone for a drill bit, comprising: 
 applying hardfacing by a welding process to grooves between insert lands on a roller cone body; and    applying hardfacing by a thermal spraying process to the insert lands.    
     
     
         10 . The method as defined in    claim 9    wherein the welding process comprises plasma transferred arc welding.  
     
     
         11 . The method as defined in    claim 9    wherein the thermal spraying process comprises at least one of HVOF, HAOF and D-gun spraying.  
     
     
         12 . The method as defined in    claim 9    further comprising heat treating the cone body and drilling insert sockets therein prior to the applying hardfacing to the inset lands.  
     
     
         13 . The method as defined in    claim 9    wherein the hardfacing applied by at least one of the welding process and thermal spraying process comprises tungsten carbide.