Cold Spray Coating for Canister Stress Corrosion Cracking
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Solution Overview
Problem
Current methods for mitigating and repairing chloride-induced stress corrosion cracking (CISCC) in hazardous waste containers are inadequate, as they either introduce thermal effects, do not apply compressive residual stresses, or cannot be performed in-situ, making them unsuitable for long-term storage applications.
Innovation Solution
The use of high-pressure cold spray technology to apply a dense, corrosion-resistant coating with compressive residual stresses directly onto the surface of hazardous waste containers, specifically targeting weld heat affected zones, both pre-service and in-service, without disturbing the containers, using materials like Ni-Cr-Mo alloys and metal matrix composites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If welding overlay cladding is used for corrosion control and substrate isolation, then corrosion resistance is improved, but tensile residual stresses and heat affected zone degradation are introduced
Solution Approach 1:
The patent replaces the thermal welding process with a mechanical cold spray process. High-velocity particles are accelerated and impacted onto the substrate surface, where they deform and bond through kinetic energy and adiabatic shear heating, eliminating thermal cycles and heat affected zones while still achieving corrosion-resistant coating deposition
Solution Approach 2:
The patent changes the fundamental process parameters from thermal (welding temperature, heat input) to mechanical (particle velocity, kinetic energy). The cold spray process uses particle velocities typically in the range of 300-1000 m/s to achieve coating deposition without thermal effects, fundamentally altering the deposition mechanism to avoid heat-affected zone problems
2Ease of repair
If traditional repair methods are used, then mitigation and repair can be performed, but the container must be removed from the overpack container and transferred through inspection and repair rings
Solution Approach 1:
The patent replaces complex mechanical transfer systems (inspection rings, repair rings, hoisting equipment) with a simplified cold spray apparatus that can be positioned and operated directly within the overpack container. The cold spray gun can be maneuvered to access the container surface through the annular gap without requiring container removal or complex transfer mechanisms
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
This approach effectively prevents CISCC initiation and propagation by applying compressive residual stresses and a corrosion-resistant layer, reducing the risk of pitting and corrosion, while allowing for in-situ application, thus enhancing the durability and safety of hazardous waste container storage systems.
Implementation Method 1
a gas stream accelerating powder particles to high velocity and impacting the particles against a container surface to which the particles bond
Implementation Method 2
The particles are cold sprayed at a temperature below the melting point of the particles
Implementation Method 3
a compressed gas stream accelerating powder particles to high velocity
Data Source
AI summary
Systems and methods for application of stress corrosion cracking resistant cold spray coatings include a method of forming a partial coating on a canister having a perimeter wall with a surface. The method may include identifying a compromised region on the surface of the wall of the canister, and impacting a substantially linear flow of particles of a powder against an area in the compromised region of the surface in a manner effective to cause the particles of the powder to bond to the surface of the wall to produce a coating on the area of the compromised region. The method may also include moving the substantially linear flow in a direction substantially parallel to the surface of the wall to cause the particles to impact an additional area of the compromised region to cause the particles to bond to the surface of the additional area.