Copper-Nickel-Tin Rod Couplings for Galling and Corrosion Resistance
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Solution Overview
Problem
Conventional couplings used in the oil and gas industry, such as sucker rod couplings, face issues with galling (wear due to adhesion) and corrosion, leading to mechanical integrity failures and costly remediation, particularly due to the lack of intrinsic galling resistance in steel or nickel alloys.
Innovation Solution
The development of spinodally-hardened copper-nickel-tin alloys with specific weight percentages, which provide high tensile strength, fatigue strength, fracture toughness, and corrosion resistance, along with unique groove designs on the exterior surface to enhance fluid flow and reduce wear, are used to create couplings that resist galling and extend equipment lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional steel or nickel alloys are used for couplings, then high tensile strength is achieved, but galling resistance is poor leading to adhesion wear and mechanical integrity failure
Solution Approach 1:
The patent applies composite materials by combining copper with nickel and tin to create a multi-phase alloy structure. The copper matrix provides ductility and corrosion resistance, while the nickel and tin phases contribute to strength and galling resistance. This composite approach resolves the contradiction by achieving both high tensile strength and superior galling resistance that cannot be obtained with conventional single-phase steel or nickel alloys.
Solution Approach 2:
The patent employs parameter changes through spinodal decomposition heat treatment to transform the microstructure of the copper-nickel-tin alloy. By controlling the decomposition temperature and time, the alloy develops a specific two-phase microstructure with optimal mechanical properties. This parameter optimization enables the material to simultaneously achieve high tensile strength and exceptional galling resistance, resolving the technical contradiction.
2Reliability
If expensive surface treatments are applied to increase galling resistance, then galling resistance is improved, but the treatments wear off requiring periodic re-application
Solution Approach 1:
The patent applies the self-service principle by incorporating galling resistance directly into the bulk material properties through spinodal decomposition. The unique two-phase microstructure provides intrinsic galling resistance that does not require external surface coatings or treatments. This self-containing approach eliminates the need for periodic re-application of surface treatments, significantly extending the effective service life of the coupling while maintaining reliable galling resistance throughout its operational lifetime.
3Strength
If couplings are made from materials with high strength, then mechanical integrity is improved, but corrosion resistance may be compromised
Solution Approach 1:
The patent resolves this contradiction through composite materials by creating a multi-phase copper-nickel-tin alloy where each phase contributes different properties. The copper matrix provides excellent corrosion resistance, while the nickel and tin precipitates provide high strength. The synergistic combination of these phases achieves both high mechanical integrity and superior corrosion resistance, eliminating the trade-off present in conventional single-phase materials.
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 spinodally-hardened copper-nickel-tin alloy couplings exhibit improved galling resistance and corrosion resistance, delaying destructive damage and extending the service life of components in hydrocarbon recovery systems, thereby reducing operational costs and maintaining mechanical functionality.
Implementation Method 1
High mechanical strength of ternary copper-nickel-tin alloys is produced by a controlled thermal treatment called spinodal decomposition
Implementation Method 2
galling resistance, and corrosion resistance. Conventional couplings are typically comprised of steel or nickel alloys which lack the full complement of preferred intrinsic characteristics, particularly galling resistance
Implementation Method 3
high tensile strength, high fatigue strength, high fracture toughness, galling resistance, and corrosion resistance
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A cold worked and spinodally-hardened copper alloy comprising from about 8 to about 20 wt% nickel, and from about 5 to about 11 wt% tin, the remaining balance being copper, and having a 0.2% offset yield strength of at least 75 ksi, is used to form a sucker rod coupling or subcoupling. Each coupling is formed from a core having two ends, each end having an internal thread. These box ends engage the pin of a sucker rod or other rod. The exterior surface of the core includes grooves running between the two ends.