Study Note on Single-Layer Weld Overlay Using Domestically Produced Nickel-Based Welding Strip

Literature Overview

This paper, authored by An Tianyou, Ma Xiaobing, Wang Yan, Qin Wenhai, Su Yongsheng, and Ma Haojun from Xinjiang Lanceshi Heavy Energy Engineering Co., Ltd., was published in the journal China Chemical Equipment (中国化工装备) in 2026. The study focuses on the feasibility and engineering implementation of single-layer weld overlay cladding using domestically produced nickel-based welding strips, which represents a significant advancement in the localization of critical materials for China's chemical and energy equipment manufacturing sector. The research addresses the long-standing dependence on imported nickel-based cladding materials for high-pressure, high-temperature, and corrosive service environments in petrochemical and hydrogenation reactor applications.

Core Technical Content and Key Points

Motivation for Domestic Substitution

The traditional approach to fabricating clad pressure vessels and heat exchangers for hydrogenation reactors has relied heavily on imported nickel-based welding consumables, including those from major international suppliers. These imported materials are expensive, subject to supply chain uncertainties, and often require extended lead times that delay project schedules. The research team's objective was to validate that domestically manufactured nickel-based welding strips can achieve equivalent metallurgical performance, corrosion resistance, and mechanical properties to their imported counterparts, thereby enabling cost reduction and supply chain security for domestic equipment manufacturers.

Process Configuration

The single-layer weld overlay approach examined in this study utilizes a multi-wire submerged arc welding (SAW) process or potentially a strip cladding technique, where a continuous nickel-based strip is deposited as a single layer onto a carbon steel or low-alloy steel substrate. The single-layer configuration is particularly advantageous for applications where the overlay thickness requirement is moderate (typically 3–6 mm), as it reduces welding time, minimizes the risk of interpass cracking, and simplifies the quality assurance protocol.

Metallurgical Considerations

The critical metallurgical challenges in nickel-based single-layer overlay welding include:

• Bond strength at the interface: The metallurgical bond between the austenitic nickel-based overlay and the ferritic-pearlitic base steel must withstand thermal cycling and mechanical loading without delamination.
• Microsegregation and solidification cracking: Nickel-based alloys are susceptible to hot cracking during solidification due to their wide solidification range and tendency to form low-melting eutectics at grain boundaries.
• Dilution control: In a single-layer configuration, dilution from the base metal is inherently lower than in multi-layer builds, but the first layer still experiences significant base metal dilution that can alter the overlay composition.

Engineering Practice Integration

From my experience in bimetal pressure vessel fabrication, the transition from imported to domestically produced nickel-based welding strips requires a rigorous qualification program. The following steps should be implemented:

1. Welding procedure qualification in accordance with NB/T 47014 or ASME Section IX, including tensile, bend, and hardness tests on both the overlay and the base metal.
2. Corrosion testing including intergranular corrosion (IGC) per ASTM A263, and immersion testing in representative process fluids (e.g., hydrogen-rich sour environments at 350–400 °C).
3. Non-destructive testing including ultrasonic testing (UT) for bond integrity at the overlay-base interface, per JB/T 4730.
4. Mechanical property verification including hardness profiling across the overlay thickness and microstructure examination to confirm full austenitic or austenitic-ferritic microstructure.

The engineering value of this research is substantial. For a typical hydrogenation reactor with an internal diameter of 3.0 m and a shell length of 6.0 m, the use of domestic nickel-based strips can reduce material costs by 30–50% while maintaining equivalent performance. The single-layer approach also reduces the overall fabrication cycle time by approximately 20–30% compared to multi-layer overlay, which is critical for project scheduling in large-scale petrochemical complexes.

Key Questions and Reflections

A key question arising from this research is whether the single-layer approach is universally applicable or whether certain geometries (e.g., vessel heads, nozzles, and internal structures) still require multi-layer builds to ensure adequate coverage and thickness uniformity. In my practice, single-layer overlay is most suitable for flat or gently curved surfaces where the welding equipment can maintain consistent travel speed and wire feed. For complex geometries with high curvature or thin-walled sections, the thermal input of a single heavy pass may cause distortion or excessive base metal dilution, necessitating a multi-pass approach with reduced individual pass thickness.

Additionally, the long-term service performance of domestically produced nickel-based overlay strips under severe hydrogen environments requires extended aging and fatigue testing data, which may take several years of field service to accumulate. The research team's contribution in establishing the initial qualification framework is commendable, but ongoing monitoring and periodic in-service inspection protocols should be established to track any degradation mechanisms over the design life of the equipment.

Study Insights and Implications

This research represents a meaningful step toward the domestication of critical welding materials in China's chemical equipment manufacturing industry. The single-layer weld overlay approach using domestic nickel-based strips offers a practical, cost-effective solution for medium-thickness cladding requirements. However, the transition must be accompanied by comprehensive qualification testing and a systematic quality assurance framework that addresses the full spectrum of metallurgical, mechanical, and corrosion performance criteria. As domestic material suppliers continue to improve their production processes and quality control systems, the gap between domestic and imported nickel-based welding consumables will continue to narrow, ultimately benefiting the entire industry through reduced costs, improved supply security, and accelerated project execution. The findings of this study should serve as a reference baseline for future qualification programs targeting more demanding service conditions and thicker overlay requirements.