Cutter rings and method of manufacture

Abstract

Disclosed herein is a ring cutter for a tunneling apparatus, the ring cutter formed by a process in one form comprising several steps. In one form, this mold is sacrificial, and may be a pair of parallel cylinders such as an outer and an inner cylinder with a gap there between. In one manufacturing process, a single mold is used to produce multiple cutters which are cast simultaneously within the single mold. In one form, the mold is formed in the final shape of the cutter, such that the cutter requires no further machining to be used in a tunneling apparatus. Another step being: disposing a volume of powdered metal, such as a nickel based alloy, into the mold. The powdered metal may then be subjected to isostatic gas pressures, and elevated sintering temperatures simultaneously (HIP) with the isostatic gas pressure to consolidate the powdered metal.

Therefore I claim: 
     
         1 . A ring cutter for a ground boring apparatus, the cutter ring formed by a process comprising the steps of:
 a. providing a mold of the cutter;   b. disposing a volume of powdered metal into the mold;   c. subjecting the powdered metal to isostatic gas pressures;   d. subjecting the powdered metal to elevated sintering temperatures simultaneously with the isostatic gas pressure to consolidate the powdered metal; and   e. wherein the elevated temperatures are sufficient to sinter the powdered metal.   
     
     
         2 . The process as recited in  claim 1  wherein the mold is sacrificial. 
     
     
         3 . The process as recited in  claim 1  wherein the temperatures used in the austenitization process exceed 1650° F. 
     
     
         4 . The process as recited in  claim 1  further comprising the step of metal injection molding. 
     
     
         5 . The process as recited in  claim 1  wherein Argon gas is used in the step of subjecting the powdered metal to isostatic gas pressures. 
     
     
         6 . The process as recited in  claim 1  wherein the elevated sintering temperatures exceed 900° F. 
     
     
         7 . The process as recited in  claim 6  wherein the elevated sintering temperatures exceed 2,400° F. 
     
     
         8 . The process as recited in  claim 7  wherein the powdered metal is a nickel-based alloy. 
     
     
         9 . The process as recited in  claim 1  wherein the isostatic gas pressures exceed 7,350 PSI. 
     
     
         10 . The process as recited in  claim 9  wherein the isostatic gas pressures exceed 15,000 PSI. 
     
     
         11 . The process as recited in  claim 9  wherein the isostatic gas pressures is less than 45,000 PSI. 
     
     
         12 . The process as recited in  claim 1  wherein the mold is substantially an inner cylinder and an outer cylinder. 
     
     
         13 . The process as recited in  claim 12  wherein multiple cutters are cast simultaneously within a single mold. 
     
     
         14 . The process as recited in  claim 1  wherein the cutter requires no further machining to be used in a tunneling apparatus. 
     
     
         15 . A method of fabricating a cutter ring for a tunneling device, the method comprising the steps of:
 a. securing an mold about the circumference of an inner ring so as to create a cavity defined by the mold and a surface of the inner ring;   b. filling the cavity with an alloy, which is in powder form, to form a cutter ring assembly;   c. sealing the cavity;   d. heating the cutter ring assembly to a selected temperature;   e. placing the heated cutter ring assembly in a hot isostatic press while the cutter ring assembly is heated to the selected temperature; and   f. subjecting the cutter ring assembly to a predetermined temperature and pressure in the hot isostatic press.