Cobalt-Based Alloy Cladding with Chromium Gradient for Wear Resistance
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Solution Overview
Problem
Claddings on metallic substrates, such as frack valves, often fail due to premature degradation, including delamination and cracking, especially under thermal cycling and complex geometries, which restricts the use of hardfacing alloys with high hardness and wear resistance.
Innovation Solution
A composite alloy cladding with a chromium gradient, potentially combined with tungsten, nickel, and silicon gradients, is metallurgically bonded to the substrate, using a method involving infiltration of cobalt powder alloys with organic carriers to prevent cracking and maintain adhesion, resulting in a fully dense, crack-free, and high-hardness coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If hardfacing alloys are applied by sintering to achieve high hardness and wear resistance, then the cladding exhibits high hardness and wear resistance, but cracking and delamination occur along seat surfaces
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the cobalt-based alloy, specifically controlling chromium content (15-30 wt%), tungsten content (5-15 wt%), and carbon content (1-3 wt%). These compositional parameter changes prevent cracking and delamination while maintaining high hardness and wear resistance, resolving the contradiction between strength and reliability.
Solution Approach 2:
The patent uses composite materials by creating a multi-layered cladding structure with a transition layer and a hardfacing layer. The transition layer contains a gradient composition that metallurgically bonds the hardfacing alloy to the substrate, preventing cracking and delamination while maintaining the high hardness and wear resistance of the hardfacing layer.
2Strength
If post-coat heat treatment is applied to improve mechanical properties of the substrate, then the mechanical properties of the substrate are improved, but the cladding is fractured
Solution Approach 1:
The patent applies preliminary action by performing the cladding process before the post-coat heat treatment of the substrate. The cladding is applied to the as-received substrate, and the subsequent heat treatment improves substrate mechanical properties without fracturing the cladding, as the cladding was already in place and designed to withstand such treatments.
Solution Approach 2:
The patent controls the thermal parameters during the cladding process and subsequent heat treatments. By optimizing the heating rate, holding temperature, and cooling rate parameters, the cladding structure is designed to withstand substrate heat treatment without fracturing, while still allowing the substrate to achieve improved mechanical properties.
3Reliability
If cladding is applied to complex geometry substrates, then the substrate can be protected, but shrinkage during deposition induces cracking and delamination
Solution Approach 1:
The patent applies local quality by creating a transition layer with gradient composition that is localized at the interface between the substrate and the hardfacing layer. This transition layer has different chemical composition and microstructure tailored for that specific location, providing metallurgical bonding and accommodating thermal expansion differences, thereby preventing cracking and delamination on complex geometry substrates.
Solution Approach 2:
The patent controls the deposition parameters including powder feed rate, heating rate, and atmospheric conditions during the cladding process. These parameter changes ensure uniform deposition on complex geometry substrates while minimizing shrinkage-induced stress that could cause cracking and delamination.
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 composite cladding exhibits enhanced hardness and wear resistance, maintaining integrity and adhesion even on complex surfaces, preventing cracking and delamination, and sustaining performance through thermal cycling.
Implementation Method 1
The assembly is heated to infiltrate the base cobalt powder alloy with molten infiltration cobalt alloy
Implementation Method 2
The assembly is heated to infiltrate the base cobalt powder alloy with molten infiltration cobalt alloy
Data Source
AI summary
In one aspect, composite articles are described herein employing cobalt-based alloy claddings exhibiting high hardness and wear resistance while maintaining desirable integrity and adhesion to surfaces of metallic substrates. A composite article, in some embodiments, comprises a metallic substrate and a composite cladding metallurgically bonded to one or more surfaces of the metallic substrate, the composite cladding including cobalt-based alloy having a chromium gradient, wherein chromium content increases in a direction from the composite cladding surface to an interface of the composite cladding with the metallic substrate.