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Detailed Explanation of Drill Pipe Wear-Resistant Strips and Internal Coating Technologies: Selection, Manufacturing Processes, and Quality Control
Author:
WHH
Source:
LONGWAY
Published:
2026-09-16
During downhole service, the outer surface of the tool joint experiences mechanical wear against the casing or wellbore wall, while the inner surface of the drill pipe is subjected to corrosion and erosion by drilling fluids. Hardbanding and internal plastic coating are the core technological solutions for addressing these two types of challenges. Based on the latest product data sheets from Hebei Longway, this paper systematically reviews the technical specifications, selection criteria, welding/coating processes, and key quality‑control considerations for hardbanding and internal coatings.
I. Wear-Resistant Strip: The “Sacrificial Layer” That Protects Joints and Casing
Wear-resistant strip It is a wear‑resistant alloy layer overlay welded onto the outer surface of drill pipe tool joints, with the primary function of protecting both the joint body and the casing. Hebei Longway offers three series of wear‑resistant strips—LW600, LW700, and LW800—whose technical specifications are as follows:
| Parameter | LW600 | LW700 | LW800 |
| Hardness (HRC) | ≥54 | ≥57 | ≥60 |
| Extend the service life of drill rods | 120% | 180% | 240% |
| Crack sensitivity | No visible cracks. | No visible cracks. | No visible cracks. |
| Repairability | excellent | excellent | Good |
| Abrasion Resistance Test (ASTM G65 Standard / Abrasion Mass Loss) | ≤0.22 mg | ≤0.18mg | ≤0.11 mg |
| Casing wear (Muller test method) | ≤38mm³ | ≤36mm³ | ≤40mm³ |
| Surface quality | Smooth and flawless | Smooth and flawless | Smooth and flawless |
| Impact resistance | excellent | excellent | Good |
Selection logic:
LW600: Hardness ≥ 54 HRC, casing wear volume ≤ 38 mm³; suitable for deep wells and production wells with stringent casing‑protection requirements.
LW700: Hardness ≥ 57 HRC, casing wear volume ≤ 36 mm³; offers a balance between wear resistance and casing protection, suitable for most conventional drilling operations.
LW800: Hardness ≥ 60 HRC, with superior wear resistance (≤ 0.11 mg), extending service life by 240%. It is suitable for highly abrasive formations (such as hard-rock drilling), but exhibits relatively high casing wear (≤ 40 mm³).
Soldering Process and Quality Control:
Wear‑resistant strip overlay welding is performed using a fully automatic numerical control welder, with the following process sequence: preheating before welding → automated overlay welding → post‑weld heat preservation → hardness testing. Key control points include: preheating to prevent quenching‑induced cracking; post‑weld heat preservation to avoid interfacial cracks; individual piece hardness inspection; and ensuring that the surface exhibits no visible cracks, with firm bonding to the joint body—no delamination or spalling.
API Standard: Wear‑resistant strip performance is evaluated in accordance with API 7CW; the API 5DP specifies that the overlay welding process must be qualified, and the surface shall be free of any visible cracks.
II. Internal Coating: A “Corrosion-Resistant Barrier” Protecting the Inner Wall of the Pipe
Internal coating Applied to the inner wall of drill pipes, it provides corrosion protection, reduces friction, and enhances hydraulic efficiency. Hebei Longway offers four types of internal coatings—LPC3000P, LPC3000P‑HD, LPC5000P, and LPC5000P‑HD—with the following technical specifications:
| Parameter | LPC3000P | LPC3000P-HD | LPC5000P | LPC5000P-HD |
| Coating Type | Epoxy phenolic powder | Epoxy phenolic powder | Epoxy phenolic powder | Epoxy phenolic powder |
| Color | Yellow | Yellow | Green | Green |
| Coating thickness (μm) | 150-300 | 250-350 | 250-350 | 300-450 |
| Maximum operating temperature | 180℃ | 196℃ | 204℃ | 214℃ |
| Abrasion resistance (sand-drop method, 1 kg/1000 revolutions) | ≥2.4 L/μm | ≥2.4 L/μm | ≥3.5 L/μm | ≥3.5 L/μm |
| Extend drill pipe life | 1-2 times | 2 times | 3-4 times | 4 times |
| Adhesion | Grade A | Grade A | Grade A | Grade A |
| Impact resistance | High | High | High | High |
| Recommended by Jing Shen | ≤5000m | ≤6500m | ≤8000m | ≤8500m |
| Bending performance | Good | Good | Good | Good |
| Surface roughness Ra (μm) | 0.5-0.8 | 0.4-0.6 | ≤0.4 | 0.25-0.4 |
| Save drilling mud power | 10%-15% | 11%-16% | 15%-20% | 20%-25% |
| pH tolerance range | 2-12.5 | 2.5-13 | 3-13 | 5-15 |
Selection logic:
LPC3000P: Suitable for standard corrosive environments, with a temperature rating of ≤180°C and a well depth of ≤5,000 m, offering excellent cost-effectiveness.
LPC3000P-HD: An upgraded version of the LPC3000P, with a thickness of 250–350 μm, a temperature resistance of 196°C, and suitability for well depths up to 6,500 m. It offers enhanced wear resistance and corrosion resistance.
LPC5000P: Based on Valspar’s epoxy‑phenolic FBE coating, with a thickness of 250–350 μm and a temperature resistance of 204°C, it is suitable for deep wells operating in corrosive environments containing H₂S, CO₂, and acidic or alkaline salts, extending service life by a factor of 3 to 4.
LPC5000P-HD: An upgraded version of the LPC5000P, with a thickness of 300–450 μm, a temperature resistance of 214°C, and suitability for well depths up to 8,500 m. It is designed for ultra-deep wells in extremely corrosive environments, offering a service life four times longer and reducing mud‑pump power consumption by 20%–25%.
Painting Process and Quality Control:
The internal coating process comprises: internal surface pretreatment (sandblasting/acid pickling) → primer application → topcoat application → curing → quality inspection. Key control points include: ensuring adhesion through surface pretreatment; maintaining film thickness within design specifications; verifying curing temperature and time to guarantee coating performance; and conducting quality inspections for adhesion, film thickness, and pinhole detection.
III. Key Points for Procurement and Acceptance
When procuring wear-resistant belts and internal coating services, the following requirements shall be clearly specified in the contract:
| Project | Technical Requirements |
| Abrasion-resistant belt type | LW600/LW700/LW800 or as specified by the customer |
| Soldering position | Tool connector male end, female end, and intermediate thickened section |
| Wear-resistant belt hardness | HRC range compatible with the selected model |
| Internal Coating Type | LPC3000P/LPC3000P-HD/LPC5000P/LPC5000P-HD or as specified by the customer |
| Coating film thickness | μm range compatible with the selected model |
| Test Report | Wear‑resistant strip hardness test report, coating adhesion and film thickness test report |
| Standard compliance | The wear-resistant strip complies with API 7CW, and the internal coating complies with NS-1/SY/T0544-2016. |
IV. Frequently Asked Questions (FAQ)
Q1: Is a harder wear strip always better?
No. The higher the hardness of the wear‑resistant band, the longer its service life; however, it may also increase wear on the casing. When selecting a material, it is essential to strike a balance between protecting the drill pipe and safeguarding the casing.
Q2: Does the internal coating affect the mechanical properties of drill pipes?
No. The internal coating is a surface‑treatment process that does not alter the mechanical properties of the pipe’s base material.
Q3: What is the main difference between the LPC5000P and the LPC3000P?
The main differences lie in the maximum operating temperature, sulfur resistance, and service life. The LPC5000P withstands temperatures up to 204°C, operates over a pH range of 3–13, and offers a service life that is 3–4 times longer; the LPC3000P tolerates temperatures up to 180°C, functions across a pH range of 2–12.5, and provides a service life that is 1–2 times longer.
Q4: Can the wear-resistant belt be repaired?
Yes. Worn wear-resistant strips can be repaired by re‑surfacing; the performance after repair is essentially equivalent to that of a newly surfaced strip (the reparability of LW800 is rated as “good”).
Q5: Can internally coated drill pipes be used in H₂S-containing wells?
Yes, but an sulfur‑resistant internal coating (such as the LPC5000P series) must be selected, and its pH tolerance range should be confirmed to encompass the operating conditions. In addition, the sulfur‑resistance of the drill pipe substrate should be carefully evaluated.
V. Summary
| Technology | Core Features | Key parameters | Selection Criteria |
| Wear-resistant strip | Protective Joint and Sleeve | Hardness, wear resistance, and casing wear amount | Formation abrasiveness and casing protection requirements |
| Internal coating | Corrosion inhibition, friction reduction, and enhanced hydraulic efficiency | Temperature resistance, pH range, membrane thickness, surface roughness | Downhole temperature, corrosive media, and hydraulic requirements |
Wear-resistant bands and internal coatings are the two core technologies for surface protection of drill pipes. Proper selection, standardized installation, and rigorous inspection are essential to ensure the long-term, reliable performance of drill pipes downhole.
Do you need to select wear-resistant bands or an internal coating for your drill rods?
Contact Hebei Longway Petroleum Equipment Co., Ltd.
Obtain professional technical consulting
Hebei Longway is equipped with fully automated wear‑resistant strip welding machines and an internal coating production line, offering LW‑series wear‑resistant strips and LPC‑series internal coating services, compliant with API 7CW and NS‑1 standards.
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