Hot-Shaping Core Coating to Prevent Titanium Adhesion
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Solution Overview
Problem
Refractory alloy cores used in isostatic pressing for manufacturing turbomachine fan blades face challenges such as deformation, chemical reactions, and adhesion with titanium alloys during high-temperature thermomechanical cycles, leading to contamination and bonding issues that hinder core reuse and increase manufacturing costs.
Innovation Solution
A coating process for the cores using a refractory metal oxide and an inorganic binder, applied in multiple layers with controlled heat treatment, to form a stable, non-reactive, anti-diffusion layer that prevents species interdiffusion and adhesion, allowing for core reuse and reduced chemical reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If nickel-based or cobalt-based metal alloys are used for the core to ensure sufficient rigidity at high temperature, then the core maintains its shape during thermomechanical cycles, but the core reacts chemically with titanium alloys forming solid solutions or intermetallic compounds leading to contamination and bonding
Solution Approach 1:
A coating layer comprising a refractory metal oxide and an inorganic binder is applied on the core surface. This coating acts as an intermediary barrier between the nickel-based or cobalt-based core material and the titanium alloy, preventing direct chemical contact while allowing the core to maintain its structural rigidity at high temperatures.
Solution Approach 2:
The core system becomes a composite structure with a nickel-based or cobalt-based alloy core providing mechanical strength and rigidity, covered by a refractory metal oxide coating with an inorganic binder that provides chemical inertness. This composite approach combines the advantageous properties of different materials to simultaneously achieve rigidity and chemical resistance.
2Object-affected harmful factors
If stop-off type products with organic binder are used to protect titanium against contamination, then the titanium is protected from air and tool contamination, but the organic binder degrades during heating and contaminates the contact zones preventing diffusion welding
Solution Approach 1:
The binder material is changed from organic to inorganic composition. This parameter change in the chemical nature of the binder eliminates degradation at high temperatures, as inorganic binders remain stable throughout the thermomechanical cycle without producing contaminating degradation products that would interfere with diffusion welding.
Solution Approach 2:
The coating is designed as a consumable protective layer that performs its function during the forming process and can be removed or degraded after use. The inorganic binder provides protection during the critical forming operation without leaving harmful residues, allowing the coating to be discarded after serving its protective purpose.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The coating process effectively prevents contamination and adhesion, enabling the reuse of cores and reducing manufacturing costs by minimizing chemical reactions and species diffusion, while maintaining the core's shape and internal cavity integrity.
Implementation Method 1
a first refractory component configured to oppose species diffusion, the first component comprising a metal oxide
Implementation Method 2
a second component configured to bind the first component so as to form a homogeneous layer, the second component comprising an inorganic binder
Implementation Method 3
Applying a heat treatment to the coated core so as to dry the solution and solidify the coating
Implementation Method 4
Applying a heat treatment to the coated core so as to dry the solution and solidify the coating
Data Source
AI summary
The invention concerns a method for coating a core (1) for producing a turbomachine part (2) by isostatic compacting, for example a leading-edge shield of a blade, the coating method comprising the steps of:—S1: covering the core (1) by means of a first solution comprising a first refractory component configured to oppose the diffusion of species, the first component comprising a metal oxide,—S2: covering the core (1) by means of a second solution comprising a second component designed to bind the first component in such a way as to form a homogeneous layer, the second component comprising a mineral binder;—S3: applying a heat treatment to the covered core (1) in such a way as to dry the solution and solidify the coating.