Cu-Ni-Sn Sucker Rod Coupling for Galling-Resistant Strength
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Solution Overview
Problem
Conventional couplings used in the oil and gas industry, such as sucker rod couplings, suffer from galling (wear due to adhesion) issues, leading to mechanical integrity failures and costly maintenance, as they lack sufficient galling resistance and corrosion protection, necessitating frequent surface treatments.
Innovation Solution
The development of spinodally-hardened copper-nickel-tin alloys with specific compositions and microstructural treatments, such as cold working and spinodal hardening, to create couplings with enhanced tensile strength, fatigue resistance, fracture toughness, and galling resistance, reducing wear and extending equipment lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional steel or nickel alloys are used for couplings, then high tensile strength can be achieved, but galling resistance is insufficient
Solution Approach 1:
The patent employs a composite material system consisting of a copper-nickel-tin alloy base material combined with a PTFE-based lubricating coating. This composite structure leverages the high ductility and corrosion resistance of the copper alloy while the PTFE coating provides exceptional galling resistance and low friction, resolving the contradiction between strength and galling resistance.
Solution Approach 2:
The patent utilizes spinodal decomposition, a thermodynamic phase separation process, to transform the microstructure of the copper-nickel-tin alloy. By controlling the composition parameters (specifically 7-11 wt% nickel and 3-9 wt% tin) and applying heat treatment, the alloy develops a unique two-phase microstructure that simultaneously achieves high tensile strength (>600 MPa) and enhanced galling resistance.
2Reliability
If expensive surface treatments are applied to increase galling resistance, then galling protection is improved, but maintenance frequency increases due to treatment wear
Solution Approach 1:
The PTFE-based lubricating coating is formulated to be self-healing and long-lasting. The coating system includes reactive primers that chemically bond to the substrate and topcoats that provide continuous PTFE lubrication. This self-sustaining system reduces maintenance frequency by providing durable, long-term galling protection without requiring frequent reapplication.
Solution Approach 2:
The patent applies different functional layers with specific properties to different aspects of the coupling surface. The primer layer provides corrosion protection and adhesion, while the PTFE topcoat provides low friction and galling resistance. This localized functional differentiation optimizes both protection and durability.
3Ease of manufacture
If conventional alloys are used, then manufacturing simplicity is maintained, but corrosion resistance is insufficient
Solution Approach 1:
The copper-nickel-tin alloy itself forms a composite microstructure through spinodal decomposition, creating intermetallic phases that provide inherent corrosion resistance. This metallurgical composite structure achieves enhanced corrosion protection without requiring additional complex manufacturing steps, maintaining ease of manufacture while improving reliability.
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 mechanical properties, delaying destructive damage and reducing maintenance costs by providing long-lasting mechanical functionality during hydrocarbon recovery operations.
Implementation Method 1
High mechanical strength of ternary copper-nickel-tin alloys is prodiced by a controlled thermal treatment called spinodal decomposition
Implementation Method 2
cold working and spinodal hardening
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.