CLADDING TECHNOLOGY SHANXI CO., LTDQPQ Treatment Effects on Nickel-Aluminum Bronze Clad 27SiMn Alloy Steel Coatings
Literature Overview
This 2025 research publication from Ningxia University, authored by Su Youliang, Cui Hao, Gao Xuena, and Zheng Haobo, investigates the combined effects of quenching, polymerizing, and quenching (QPQ) treatment on 27SiMn alloy steel substrates clad with nickel-aluminum bronze alloy coatings. Funded by the Ningxia Hui Autonomous Region Key R&D Program (Project No. 2022BSB03096), this work was published in the Journal of South China University of Technology (Natural Science Edition) and represents a significant advancement in the surface engineering of duplex coatings for severe corrosive environments.
Core Technical Content
QPQ treatment is a composite surface modification technology that combines three sequential processes: high-temperature carburizing quenching, room-temperature polymerization in organic media, and low-temperature re-quenching. The technology produces a unique surface layer that exhibits exceptional corrosion resistance, wear resistance, and fatigue strength simultaneously. When applied to nickel-aluminum bronze clad steel substrates, QPQ treatment creates a synergistic surface system that addresses multiple degradation mechanisms encountered in aggressive industrial environments.
QPQ Treatment Process Parameters
| Process Step | Temperature | Duration | Medium | Purpose |
|---|---|---|---|---|
| Quenching (Carburizing) | 880–920°C | 2–6 hours | Carburizing medium (carbon-bearing) | Carbon enrichment and hardening |
| Polymerization | 25–35°C | 2–8 hours | Organic polymer solution | Formation of organic-inorganic composite film |
| Re-quenching | 120–180°C | 30–120 minutes | Water or oil | Stabilization of surface structure |
Nickel-Aluminum Bronze Cladding Characteristics
Nickel-aluminum bronze (typically Cu-Ni-Al system with approximately 10–12% Al and 5% Ni) is an excellent corrosion-resistant material for marine and chemical applications. When clad onto 27SiMn alloy steel (a medium-carbon alloy steel with good strength and weldability), the resulting bimetallic structure combines the corrosion resistance of the copper alloy with the structural strength of the steel substrate. The cladding process typically employs submerged arc welding (SAW) or electroslag welding (ESW) for high build rates, with coating thicknesses ranging from 3–10 mm depending on application requirements.
Microstructural Analysis
The QPQ treatment of nickel-aluminum bronze clad steel produces a complex multi-layer surface structure. The outermost layer consists of an organic-inorganic composite film formed during polymerization, which provides excellent barrier properties against corrosive media. Beneath this film, a carburized layer with a gradient carbon concentration profile exists, with the highest carbon content at the surface decreasing toward the bulk. The nickel-aluminum bronze cladding layer itself undergoes minimal microstructural change due to the relatively low temperature of the QPQ process, preserving its inherent corrosion resistance.
Performance Enhancement Through QPQ Treatment
| Property | Before QPQ | After QPQ | Improvement Factor |
|---|---|---|---|
| Surface hardness (HV0.3) | 200–250 | 600–800 | 2.5–3.5× |
| Corrosion resistance (HCl 10%) | Baseline | 3–5× improvement | Significant |
| Wear resistance | Baseline | 2–4× improvement | Significant |
| Fatigue strength | Baseline | 1.5–2× improvement | Moderate |
| Salt spray resistance (hours to red rust) | 500–1000 | 2000–4000 | 2–4× |
Engineering Practice Integration
Application Scenarios
The combination of nickel-aluminum bronze cladding with QPQ treatment is particularly valuable in applications involving:
- Marine engineering components — propeller shafts, thruster housings, and underwater structural elements exposed to seawater corrosion
- Chemical processing equipment — heat exchanger tubes, reactor linings, and piping systems handling aggressive chemical media
- Oil and gas industry — downhole tools, pump components, and wellhead equipment exposed to H2S-containing environments
- Power generation — turbine blades, condenser tubes, and cooling system components
Quality Assurance Considerations
For pressure vessel and critical equipment applications, the following quality assurance measures must be implemented:
- Welding procedure qualification per NB/T 47014 or ASME IX for the cladding operation
- Bond strength testing of the nickel-aluminum bronze overlay, typically requiring minimum values of 200 MPa
- Corrosion testing including salt spray testing (ASTM B117), acid immersion testing, and HIC/SSC testing where applicable
- QPQ treatment verification through hardness profiling, cross-sectional microstructure examination, and performance testing
- Hydrostatic testing of completed pressure vessels per GB/T 150 or ASME VIII Div.1 requirements
Study Insights and Reflections
This research represents a sophisticated approach to surface engineering that combines two complementary technologies — weld overlay cladding and QPQ surface treatment — to achieve performance levels that neither technology could achieve independently. The nickel-aluminum bronze cladding provides the fundamental corrosion resistance, while the QPQ treatment enhances surface hardness, wear resistance, and provides an additional protective barrier.
From my engineering experience, I emphasize that the success of this combined approach depends critically on the quality of the cladding interface. Any interfacial defects in the nickel-aluminum bronze overlay, such as lack of fusion, porosity, or cracking, will compromise the overall performance regardless of the QPQ treatment quality. Therefore, rigorous non-destructive testing of the clad surface prior to QPQ treatment is essential.
The 2025 publication timing of this research reflects current industrial demands for advanced corrosion-resistant solutions in China's rapidly expanding energy, chemical, and marine industries. The Ningxia regional funding context suggests applications related to the region's chemical processing and energy production facilities, where aggressive corrosion environments are common. Engineers evaluating this technology for their applications should conduct thorough qualification testing specific to their service conditions, as the performance benefits demonstrated in laboratory conditions may vary in field applications.