Turbine Casing Repair With Butter Layers to Prevent Thermal Cracking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Turbine casings made of nodular cast iron face issues with casting defects, material fatigue, and thermal stress-induced cracking, leading to high repair costs and potential failure during thermal cycling due to inadequate welding methods and material mismatch.
Innovation Solution
A method involving the application of butter layers made of nickel or nickel alloys followed by fill layers of low carbon steel to repair nodular cast iron casings, with controlled heat input and thermal expansion matching, to enhance durability and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If hot welding is used to repair nodular cast iron casings, then the repair strength can be improved, but the high preheat temperature causes deformation of the casing
Solution Approach 1:
The patent changes the temperature parameter from high preheat (594°C or higher) to low preheat (200-400°F), fundamentally altering the thermal conditions of the welding process to avoid deformation while maintaining repair effectiveness
Solution Approach 2:
The patent applies a multi-layer welding structure with different material compositions: a nickel-based butter layer for stress reduction, an intermediate layer for transition, and a final fill layer for strength, creating local material optimization at different depths
2Ease of operation
If cold welding with Ni-Fe or Ni-Fe-Mn alloys is used to match the strength of nodular cast iron, then the welding ease is improved, but the low coefficient of thermal expansion causes failure during thermal cycling
Solution Approach 1:
The patent uses different materials for different functions: nickel-based alloy for stress accommodation at the interface, and low carbon steel for structural strength in the fill layer, optimizing each region's properties
Solution Approach 2:
The patent creates a composite welding structure combining nickel-based alloy and low carbon steel in specific layers, leveraging the advantages of both materials while mitigating their individual disadvantages
3Manufacturing precision
If welding is performed on finish machined parts, then the repair precision is improved, but the risk of deformation and cracking increases
Solution Approach 1:
The patent applies a butter layer preliminary coating on the machined surface before performing the final weld, preparing the surface to absorb stresses and prevent cracking during subsequent welding operations
4Reliability
If the casing is scrapped and replaced with a new one, then the reliability is improved, but the manufacturing cost and operational delay increase
Solution Approach 1:
The patent recovers the defective casing by repairing it through controlled welding rather than discarding it, extending the component's service life and avoiding the time and cost of manufacturing a new casing
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 method effectively repairs nodular cast iron casings by reducing the risk of cracking and deformation, ensuring the repaired region expands and contracts similarly to the base material, thereby extending the lifespan and reducing operational delays and costs.
Implementation Method 1
A method involving the application of butter layers made of nickel or nickel alloys followed by fill layers of low carbon steel to repair nodular cast iron casings
Implementation Method 2
ensuring the repaired region expands and contracts similarly to the base material
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A casing component is configured to form part of a flow path in a turbine. The casing component includes a base (12) made of nodular cast iron, and a repaired region (14) in the base. The repaired region includes a butter layer (32) applied on the base and a fill layer (34) applied on the butter layer.