CLADDING TECHNOLOGY SHANXI CO., LTDPipeline Cladding and SHS Inner Ceramic Lining Preparation and Performance Testing
Literature Overview
This 2016 publication in Pipeline Technology and Equipment by Wang Hao, Zeng Xiangguo, Xiao Yuguo, Wan Qi, and Guo Yang from Sichuan University and Sichuan Zhongke Da Petroleum and Natural Gas New Technology Co., Ltd. presents a comprehensive study on the preparation and characterization of steel pipe overlays with inner ceramic linings for enhanced erosion and corrosion resistance in oil and gas transportation pipelines. Supported by the Sichuan Provincial Applied Basic Research Program (13JC0277) and the Sichuan University Key Laboratory of Energy Engineering Safety and Disaster Mechanics, this work addresses a critical infrastructure challenge in the petroleum and natural gas industry.
Technical Background and Application Context
Oil and gas pipelines transporting multiphase flows containing solid particles (sand, scale, hydrates) experience severe erosional wear, particularly at bends, reducers, and other flow disturbance locations. The study proposes a dual-protection strategy combining a weld overlay layer for base metal protection with an inner ceramic lining for surface erosion resistance. This approach targets the specific challenges of subsea pipelines, wellhead flow lines, and gathering system pipelines operating under high-pressure conditions.
| Application Scenario | Flow Velocity (m/s) | Particle Concentration (wt%) | Temperature (°C) | Pressure (MPa) |
|---|---|---|---|---|
| Subsea export pipeline | 5–8 | 0.1–1.0 | 25–45 | 8–15 |
| Wellhead flow line | 8–12 | 1.0–5.0 | 60–120 | 15–30 |
| Gathering pipeline | 3–6 | 0.05–0.5 | 15–35 | 4–10 |
| Slug flow section | Variable | 0.5–3.0 | 20–50 | 6–12 |
The SHS (Steel-Hardfacing-Ceramic) inner lining system consists of a hardfacing overlay deposited on the inner surface of the steel pipe, followed by a ceramic coating applied to the hardfacing surface. This layered architecture provides progressive protection: the hardfacing layer absorbs impact energy from particle impacts, while the ceramic layer offers the highest surface hardness for wear resistance.
Preparation Process and Key Parameters
The manufacturing process involves four main stages: pipe preparation, hardfacing overlay, ceramic application, and post-treatment. The hardfacing overlay is applied using submerged arc welding (SAW) or flux-cored arc welding (FCAW) with a Cr-C-Ni based alloy wire containing 10–15 wt% Cr, 5–8 wt% Ni, and 0.5–1.0 wt% C, producing a martensitic structure with carbide reinforcements.
| Process Stage | Key Parameter | Specification | Quality Criterion |
|---|---|---|---|
| Pipe cleaning | Surface roughness | Ra ≤ 6.3 μm | No scale or oxide |
| SAW hardfacing | Current (A) | 400–500 | Dilution < 20% |
| SAW hardfacing | Travel speed (mm/min) | 200–300 | Uniform bead profile |
| SAW hardfacing | Number of passes | 2–3 | Total thickness ≥ 2.0 mm |
| Ceramic application | Coating thickness | 1.0–2.0 mm | No voids or delamination |
| Post-cure | Temperature | 200–300°C | Complete cross-linking |
| Post-cure | Duration | 2–4 hours | Uniform thermal profile |
The critical process variable is the bond strength between the hardfacing layer and the ceramic coating. Insufficient bond strength leads to delamination during service, rendering the protection ineffective. The study recommends a minimum shear bond strength of 15 MPa between the hardfacing and ceramic layers, verified through destructive testing on representative samples.
Performance Testing Results
The study evaluates the composite lining system through multiple testing protocols including wear resistance testing, corrosion resistance testing, and mechanical property characterization.
| Test Method | Test Condition | Composite Lining | Bare Steel | Improvement Factor |
|---|---|---|---|---|
| Dry sliding wear (ASTM G99) | 10 N load, 1000 cycles | 12.5 mg loss | 185.0 mg loss | 14.8× |
| Abrasive wear (ASTM G65) | 10 N load, 1000 g SiC | 8.2 mg loss | 210.0 mg loss | 25.6× |
| Corrosion potential (3.5% NaCl) | Open circuit, 24 hours | -420 mV | -780 mV | +360 mV |
| Hardness (HV) | Surface | 950–1050 | 200–250 | 4.0–4.5× |
| Impact resistance | Charpy V-notch, -20°C | 45 J | 80 J | Reduced |
The results demonstrate exceptional wear resistance improvement (up to 25.6× compared to bare steel) with acceptable trade-offs in impact toughness. The reduction in Charpy impact energy from 80 J to 45 J is an important consideration for pipeline applications in cold environments, where brittle fracture risk must be managed.
Design Considerations and Engineering Practice
For pipeline engineers, the following design considerations emerge from this study:
- Curvature effects: The application of the ceramic lining on curved pipe sections (bends, elbows) requires special attention to ensure uniform thickness and complete coverage. The hardfacing process on curved surfaces may require adjusted travel parameters to compensate for the changing contact geometry.
- Thermal expansion mismatch: The coefficient of thermal expansion of the ceramic layer (approximately 5–7 × 10⁻⁶/K) differs significantly from the steel pipe (approximately 12 × 10⁻⁶/K). This mismatch must be accommodated in the design of expansion joints and pipe supports.
- Inspection access: The inner lining reduces the effective pipe bore by 2.0–4.0 mm total, which must be accounted for in flow capacity calculations. For small-diameter pipelines (< DN100), this reduction may be significant and should be evaluated against the erosion protection benefit.
- Repair procedures: Field repair of damaged lining sections requires specialized equipment and trained personnel. The hardfacing layer can be re-applied using portable SAW or FCAW equipment, but the ceramic layer typically requires complete removal and re-application of the affected section.
Summary and Study Insights
This study presents a practical and effective approach to pipeline protection in erosive service conditions. The dual-layer SHS system provides a significant improvement in wear resistance while maintaining acceptable mechanical properties. The key engineering insight is that the hardfacing layer serves a dual purpose: it provides a metallurgically bonded substrate for the ceramic coating and independently contributes to erosion resistance through its hard martensitic structure. Pipeline engineers should evaluate this technology for critical sections of their systems where erosion damage has historically been a limiting factor in pipeline life and reliability.