Preparation method of boron nitride ceramic shell for titanium and titanium alloy precision casting

Abstract

The invention relates to a method for preparing boron nitride ceramic molding shell, which is used for titanium and titanium alloy accurate casting. It belongs to field of shaping thermo-stable ceramic molding shell material. The invention comprises following steps: preparing coating slurry with refined boron nitride powder and binding agent zirconium acetate or silica sol according to proportion by weight of 3:1; immersing wax tank into said coating slurry to make slurry be coated on wax mold evenly; spreading sand, spreading boron nitride powder on wax mold; repeating said dip-coating and sand-spreading steps for 1 to 2 times after drying and hardening; preparing slurry with binding agent and mullet powder, back coating with prepared slurry for 3-5 times; drying, demolding, and sintering wax mold with several coating layers under condition of 900-1100 Deg. C and nitrogen; getting boron nitride ceramic molding shell material.

Description

technical field [0001] The invention relates to a method for preparing a boron nitride ceramic shell used for precision casting of titanium and titanium alloys. The invention belongs to the technical field of high-temperature-resistant ceramic formwork material molding technology. Background technique [0002] Titanium and titanium alloys are widely used in the aerospace industry, energy industry, marine transportation industry, and chemical industry due to their low density, high specific strength, and a series of excellent properties such as corrosion resistance. However, titanium and titanium alloys have high chemical activity at high temperatures, and they need to chemically react with various commonly used refractory materials. This requires the refractory materials and binders used in titanium alloy casting to have very high chemical stability. At present, the shells for titanium alloy precision casting that are widely used can be roughly divided into: graphite shell...

AI Technical Summary

Problems solved by technology

The tungsten surface layer melting model shell α must be dewaxed by solvent, which is harmful to human health and also pollutes the environment; in addition, the tungsten surface layer shell is roasted in a reducing atmosphere, and the mold material deposited on the surface of the shell is dewaxed The ash is difficult to burn off, and it is easy to react with liquid titanium during pouring, forming pores on the surface of the casting

Zirconia, yttrium oxide and other oxides that are less reactive with titanium liquid used in the surface layer and adjacent layer coatings of oxide ceramic shells have higher performance; the surface coating with yttrium oxide as a filler has better casting performance , but yttrium oxide is prone to hydration, and its slurry is very sensitive to pH changes and is easy to gel

In addition, the oxide ceramic shell cannot avoid the formation of an α fouling layer on the surface of the casting, and its thickness ranges from 0.02 to 0.2 mm.