Hard alloy functionally graded material molding method

Abstract

A hard alloy functionally graded material molding method, comprising: firstly, mixing an additive with an alloy raw material to obtain a mixture; then placing the mixture obtained from the above step into a composite die set for composite pressure molding, so as to obtain a blank; the composite die set comprise outer layer high-expansion coefficient dies, an intermediate transition layer die set, and inner layer low-expansion coefficient dies; and finally, sintering the above blank to obtain the hard alloy functionally graded composite material. The multi-component hard alloy functionally graded composite material which is large in size, has a complex outline structure and is free from obvious interfaces is prepared. In a thickness direction, the sintering molded functionally graded material attains gradient grain structures that have different components and different grain sizes and are free from obvious interfaces.

What is claimed is: 
     
         1 . A molding method for a hard alloy functionally graded material, comprising:
 A) mixing an additive with an alloy raw material to obtain a mixture;   B) placing the mixture obtained from the above step into a composite die set for composite pressure molding to obtain a blank;   the composite die set comprises an outer layer die with a high expansion coefficient, an intermediate transition layer die set, and an inner layer die with a low expansion coefficient; and   C) sintering the blank to obtain the hard alloy functionally graded material.   
     
     
         2 . The molding method according to  claim 1 , wherein the mass percentage of the alloy raw material in the mixture is 50% to 85% and the mass percentage of the additive in the mixture is 15% to 50%. 
     
     
         3 . The molding method according to  claim 1 , wherein step A) comprises:
 mixing the additive and a first alloy raw material to obtain a mixture for surface layer; mixing the additive and a second alloy raw material to obtain a mixture for intermediate layer; and mixing the additive and a third alloy raw material to obtain a mixture for inner layer.   
     
     
         4 . The molding method according to  claim 3 , wherein the Fisher particle size of the mixture for surface layer is less than or equal to 3 μm, the Fisher particle size of the mixture for intermediate layer is 0.5 μm to 5 μm, and the Fisher particle size of the mixture for the inner layer is 3 μm to 30 μm. 
     
     
         5 . The molding method according to  claim 3 , wherein the alloy raw material comprises a hard phase and a soft phase;
 the hard phase is tungsten carbide and the soft phase is selected from cobalt, iron and nickel.   
     
     
         6 . The molding method according to  claim 5 , wherein the mass percentage of the hard phase in the first alloy raw material is 93% to 97%, the mass percentage of the hard phase in the second alloy raw material is 84% to 95%, and the mass percentage of the hard phase in the third alloy raw material is 75% to 90%. 
     
     
         7 . The molding method according to  claim 1 , wherein the composite pressure molding is selected from warm compaction, injection molding and hot isostatic pressing molding, or a combination thereof. 
     
     
         8 . The molding method according to  claim 1 , wherein the additive is selected from the group comprising of polyethylene, paraffin, polyethylene glycol, polypropylene, polystyrene, stearic acid, dimethyl phthalic acid, dibutyl phthalic acid and EVA, or a mixture thereof. 
     
     
         9 . The molding method according to  claim 1 , wherein degreasing treatment is performed before the sintering of the blank, and the degreasing treatment is thermal degreasing and/or solvent degreasing. 
     
     
         10 . The molding method according to  claim 1 , wherein the sintering is vacuum pressure sintering or hot isostatic pressing sintering.