Investment casting compositions, molds and related methods

Abstract

Various embodiments of a slurry composition for investment casting and a method of forming such composition are disclosed. The slurry composition can include a refractory material, a binder, a solvent, and a thixotropic agent that includes fibrillated fibers. The slurry composition can also include a filler that includes glass bubbles.

1 . A slurry composition for investment casting comprising:
 a refractory material;   a binder;   a solvent;   glass bubbles; and   a thixotropic agent comprising fibrillated fibers.   
     
     
         2 . The composition of  claim 1 , wherein the fibrillated fibers comprise organic fibers. 
     
     
         3 . The composition of  claim 2 , wherein the organic fibers comprise high-density polyethylene. 
     
     
         4 . The composition of  claim 1 , further comprising an aluminum phyllosilicate clay. 
     
     
         5 . The composition of  claim 1 , wherein the fibrillated fibers are present in an amount of at least 0.005 weight percent and no greater than 1.5 weight percent, based on the overall weight of the composition. 
     
     
         6 . The composition of  claim 1 , wherein the composition has an overall solids content ranging from 45 weight percent to 85 weight percent, based on the overall weight of the composition. 
     
     
         7 . The composition of  claim 1 , wherein the binder comprises colloidal silica. 
     
     
         8 . The composition of  claim 1 , wherein the composition comprises a working viscosity of 2 Pascal·seconds when subjected to a shear stress of at least 0.1 N/m 2  and at most 100 N/m 2 , as measured according to the Method for Measuring Viscosity. 
     
     
         9 . The composition of  claim 1 , wherein the binder comprises a styrene-butadiene latex. 
     
     
         10 . The composition of  claim 1 , wherein the binder comprises a polyvinyl butyral resin. 
     
     
         11 . An investment casting mold made using the composition of  claim 1 . 
     
     
         12 . A method of making an investment casting mold comprising:
 coating a sacrificial pattern with a prime layer comprising a first refractory slurry and a first refractory stucco;   at least partially hardening the prime layer;   coating the prime layer with an intermediate layer comprising a second refractory slurry and a second refractory stucco;   at least partially hardening the intermediate layer;   coating the intermediate layer with a backup layer comprising the composition according to  claim 1 ; and   at least partially hardening the backup layer.   
     
     
         13 . The method of  claim 12 , wherein the investment casting mold has a modulus of rupture of at least 0.5 MPa and no greater than 10 MPa after being fully hardened. 
     
     
         14 . A composition for investment casting comprising:
 a refractory material;   glass bubbles; and   a thixotropic agent comprising fibrillated fibers.   
     
     
         15 . The composition of  claim 14 , further comprising a binder and a solvent. 
     
     
         16 . The composition of  claim 15 , wherein the composition comprises a viscosity at the onset of flow of at least 5 Pascal·seconds and no greater than 50 Pascal·seconds, as measured according to the Method for Measuring Viscosity. 
     
     
         17 . The composition of  claim 14 , wherein the composition is a dry composition. 
     
     
         18 . A method of forming a slurry composition for investment casting, comprising:
 providing the dry composition of  claim 17 ; and   combining the dry composition with at least one of a binder and a solvent to form the slurry composition.   
     
     
         19 . An investment casting mold comprising:
 a prime layer;   an intermediate layer disposed on the prime layer;   a backup layer disposed on the intermediate layer; and   a seal layer disposed on the backup layer;   wherein at least one of the prime layer, intermediate layer, backup layer, and seal layer comprises a slurry composition comprising a refractory material, glass bubbles, and a thixotropic agent comprising fibrillated fibers.   
     
     
         20 . (canceled)