Oil-Well Pipe Thread Coatings for One-Side Plating Galling Resistance
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Solution Overview
Problem
Existing oil-well metal pipes face challenges in maintaining galling resistance when a plating layer is formed on only one of the pin and box contact surfaces, with existing solutions not adequately addressing the relationship between the configuration of the contact surface without a plating layer and galling resistance.
Innovation Solution
The oil-well metal pipe incorporates a zirconium oxide coating on one of the pin or box contact surfaces, followed by a first resin coating, a plating layer on the other surface, and a second resin coating on the plating layer, enhancing galling resistance through improved adhesiveness and durability of the resin coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a plating layer is formed on only one of the pin or box contact surfaces, then productivity and production cost are improved, but galling resistance deteriorates
Solution Approach 1:
The contact surfaces are segmented into two types: one surface receives a plating layer (e.g., Zn-Ni plating) while the other surface receives only a resin coating without plating. This segmentation allows selective application of protective layers based on functional requirements, improving productivity while maintaining adequate galling resistance through the resin coating on the non-plated surface.
Solution Approach 2:
Different local qualities are applied to different contact surfaces: one surface has enhanced protection with plating layer plus resin coating, while the other surface has resin coating alone. This local differentiation optimizes the balance between productivity (reducing plating operations) and galling resistance (maintaining protection where needed).
2Reliability
If compound grease containing heavy metal powder is used to improve galling resistance, then galling resistance is improved, but environmental harm increases
Solution Approach 1:
The harmful heavy metal powder (dopes) is extracted and removed from the lubricant composition. Instead, the patent uses a resin-based coating system that provides galling resistance without environmentally harmful substances, thereby eliminating the contradiction between galling resistance and environmental protection.
Solution Approach 2:
The lubricant composition is changed from heavy metal powder-based compound grease to a resin-based coating system. This parameter change in the lubricant material eliminates environmental harm while maintaining galling resistance through the resin coating's friction-reducing properties.
3Reliability
If resin coating is applied on contact surface without plating layer, then galling resistance is maintained, but coating peeling may occur
Solution Approach 1:
A surface treatment (such as phosphating or other primer applications) is performed preliminarily on the contact surface before applying the resin coating. This preliminary action creates a stable base layer that enhances adhesion and prevents peeling, allowing the resin coating to maintain galling resistance without compromising coating stability.
Solution Approach 2:
A composite coating structure is used consisting of multiple layers: a base treatment layer (such as phosphate coating or primer) combined with the resin coating. This composite structure provides both strong adhesion to prevent peeling and effective galling resistance through the resin layer's lubricating properties.
Data Source
AI summary
Provided is an oil-well metal pipe which has excellent galling resistance even when a plating layer is formed on or above a contact surface of only one of a pin and a box. An oil-well metal pipe (1) according to the present disclosure includes: a pin (40) including a pin contact surface (400) with an external thread part (41); and a box (50) including a box contact surface (500) with an internal thread part (51). The oil-well metal pipe (1) according to the present disclosure further includes: a zirconium oxide coating (100) formed on one of the pin contact surface (400) and the box contact surface (500); a first resin coating (310) formed on or above the zirconium oxide coating (100); a plating layer (200) formed on or above the other of the pin contact surface (400) and the box contact surface (500); and a second resin coating (320) formed on or above the plating layer (200).