Abstract
This paper focuses on the optimization of the rapid investment casting process for gas turbine blades, addressing the issues of time-consuming and costly trials in determining mold dimensions in traditional investment casting. By adopting 3D printing and finite element analysis, an improved casting process is proposed, resulting in high-quality castings.

Keywords: rapid investment casting; 3D printing; finite element analysis; thermal stress
1. Introduction
The traditional investment casting process involves multiple steps, including preliminary process formulation, mold making, wax pattern creation, assembly, shell making, dewaxing, firing, pouring, and inspection. Issues such as mold cracking and repeated trials for dimension adjustments can lead to extended timelines and high costs. To overcome these challenges, this study integrates additive manufacturing (3D printing) with investment casting and analyzes the causes of mold shell cracking.
2. Rapid Investment Casting of Gas Turbine Blades
2.1 Process Overview
Rapid investment casting combines 3D printing technology with the traditional investment casting process. The key steps are:
- Production of ABS Pattern: Utilize Fused Deposition Modeling (FDM) 3D printing to create an ABS resin prototype of the blade.
- Assembly of Casting Module: Bond the ABS pattern with the wax pouring system to form a casting module.
- Shell Making: Apply five layers of coating and sand, ensuring controlled density and viscosity of the coating material.
- Dewaxing and ABS Removal: Remove the wax and ABS material to form the casting cavity.
- Firing: Bake the shell to improve its resistance to high temperatures and thermal stress during pouring.
- Pouring: Pour molten metal into the shell to obtain the casting.
Table 1: Coating and Sand Recipe
Layer | Coating | Binder | Powder Material | Sand | Particle Size/Mesh |
---|---|---|---|---|---|
1 | Silica Sol | – | White Corundum | 70 | 30/60 |
2 | – | – | White Corundum | 30 | 60/100 |
3 | – | – | Bauxite | 30 | 60/100 |
4 | – | – | Coal Gangue | 16 | 30/60 |
5 | – | – | Coal Gangue | 16 | 30/60 |
2.2 Experimental Results
The casting process was successful, but initial trials encountered issues such as mold shell cracking and surface defects on the cast blade.
3. Analysis and Optimization of Mold Shell Cracking
3.1 Deformation Coordination Equation
To analyze the thermal stress state of the ABS prototype and casting shell, a deformation coordination equation was established. Assuming the ABS prototype is an infinitely long annular cylinder and the casting shell is a cylinder tightly wrapped around it:
Where X1 and X2 represent the deformation of the ABS prototype and casting shell, respectively; b is the outer diameter of the ABS prototype; α1 and α2 are the thermal expansion coefficients; σ1 and σ2 are the stresses; E1 and E2 are the elastic moduli; and Δt is the temperature change.
3.2 Thermal Stress Analysis
Finite element analysis was conducted to simulate the internal stress situation in the casting shell caused by the interaction between the ABS prototype and the casting shell during thermal expansion.
The analysis revealed that the maximum stress is concentrated at the blade’s inlet and outlet edges, where the curvature is the largest and most prone to cracking.
3.3 Optimization Measures
- Modify Blade Model: Increase the radius of the inlet and outlet edges to reduce stress.
- Optimize Internal Structure of ABS Prototype: Use a grid structure for the internal parts to reduce stress impact.
- Increase Shell Thickness: Change from five and a half layers of sand to six and a half layers to improve stress resistance.
4. Conclusion
This study successfully applied rapid investment casting technology to produce gas turbine blades using 3D printing. By analyzing and optimizing the process, issues such as mold shell cracking were addressed, leading to the production of high-quality castings. Rapid investment casting offers significant advantages in reducing time and costs, making it a practical solution for the development and research of difficult-to-cast components.