CLADDING TECHNOLOGY SHANXI CO., LTDDevelopment of Layered Laminar Cladding Materials
Overview of the Study
This paper presents the development of a layered laminar cladding material system designed to address the inherent trade-off between wear resistance and toughness in conventional monolithic cladding materials. The concept involves depositing alternating layers of hard and tough materials to create a composite overlay that combines the beneficial properties of each constituent layer. This approach draws inspiration from natural composite structures and established bimetallic manufacturing techniques.
Design Philosophy and Material System
Layered Architecture
The laminar cladding system consists of alternating layers of two distinct materials:
| Layer Type | Composition | Hardness (HV) | Function |
|---|---|---|---|
| Hard layer | High-Cr high-C (Cr 20–30%, C 2.5–3.5%) | 750–850 | Abrasive wear resistance |
| Tough layer | Low-C Ni-Cr (Ni 8–12%, Cr 3–5%, C 0.3–0.5%) | 280–350 | Impact resistance; crack arrest |
| Interface layer | Graded composition | 450–550 | Stress distribution; bonding |
The optimal layer thickness ratio was determined to be 2:1 (hard:tough) for most industrial applications, with the hard layer providing the primary wear resistance surface and the tough layer serving as a crack arrestor and stress relief layer.
Manufacturing Methodology
The laminar cladding was produced using a multi-pass submerged arc welding (SAW) technique with alternating flux-cored wires. The process sequence is as follows:
- Substrate preparation: Surface cleaning, preheating to 150–200 °C, and optional surfacing pass to ensure good bonding.
- Hard layer deposition: Using high-alloy flux-cored wire with high carbon and chromium content, deposited in 2–3 passes.
- Tough layer deposition: Using low-alloy Ni-Cr flux-cored wire, deposited in 1 pass.
- Repetition: Steps 2–3 repeated for the desired number of layer pairs.
- PWHT: Optional solution treatment at 1050 °C followed by controlled cooling.
Welding Process Parameters
| Parameter | Hard Layer | Tough Layer |
|---|---|---|
| Wire composition | Cr 25%, C 3.0%, Mo 2% | Ni 10%, Cr 4%, C 0.4% |
| Current | 350–400 A | 300–350 A |
| Voltage | 32–36 V | 28–32 V |
| Travel speed | 250–300 mm/min | 200–250 mm/min |
| Wire feed speed | 12–14 m/min | 10–12 m/min |
| Flux type | Basic low-silica | Rutile medium-silica |
| Pass thickness | 3–4 mm | 2–3 mm |
Performance Characterization
Mechanical Properties
The layered laminar cladding exhibits superior combined properties compared to monolithic alternatives:
| Property | Monolithic Hard Clad | Monolithic Tough Clad | Layered Laminar Clad |
|---|---|---|---|
| Surface hardness (HV) | 800–850 | 300–350 | 750–800 |
| Core toughness (CVN, J) | 5–10 | 40–55 | 30–40 |
| Abrasive wear rate (mg/N·m) | 0.03–0.05 | 0.25–0.35 | 0.05–0.08 |
| Impact-abrasion resistance | Poor | Moderate | Good |
| Fatigue life (cycles) | 10⁵–10⁶ | 10⁷–10⁸ | 10⁷–10⁸ |
The layered approach achieves approximately 80% of the wear resistance of the monolithic hard cladding while maintaining 70% of the toughness of the monolithic tough cladding. This represents a substantial improvement in the overall performance envelope.
Microstructural Analysis
Metallographic examination reveals several important features:
- Hard layer: Martensitic matrix with abundant M₇C₃ and M₂₃C₆ carbides, some ledeburite-type eutectic structure
- Tough layer: Pearlite-ferrite matrix with fine dispersed carbides, good ductility
- Interface: A diffusion zone of 50–100 μm with graded composition, no interfacial cracks observed
- Columnar grains: Present in both layer types, oriented perpendicular to the interface
The absence of interfacial cracking is attributed to the careful control of welding parameters and the thermal compatibility between the alternating layers. The diffusion zone provides a gradual transition in properties, reducing stress concentrations at the interface.
Engineering Application and Defect Control
Application Scenarios
The layered laminar cladding material is particularly suited for applications involving combined impact and abrasive loading:
- Crushing equipment: Jaw crusher plates, cone crusher mantles
- Mining equipment: Shovel teeth, bucket liners, conveyor idlers
- Cement grinding: Mill liners, separator components
- Material processing: Chutes handling abrasive granular materials
- Earthmoving equipment: Dozer blades, scraper buckets
Defect Prevention Measures
| Potential Defect | Root Cause | Prevention Strategy |
|---|---|---|
| Interface cracking | Thermal mismatch; residual stress | Optimize layer thickness; control cooling rate |
| Delamination | Poor wetting; flux contamination | Surface preparation; flux quality control |
| Uneven hardness | Parameter drift; wire composition variation | In-process monitoring; wire lot control |
| Excessive dilution | High heat input; thin first pass | Reduce heat input; increase first pass thickness |
| Hydrogen cracking | Moisture in flux; high hardness | Flux baking; post-weld bake at 200 °C |
Study Insights and Reflections
This paper presents a compelling engineering solution to one of the most persistent challenges in cladding technology: the inherent antagonism between hardness (wear resistance) and toughness (impact resistance). The layered laminar approach elegantly circumvents this limitation by creating a composite structure where each layer performs its designated function optimally.
A key insight from this study is that the layer thickness ratio is critical to performance optimization. Too thin a tough layer fails to arrest cracks effectively, while too thick a hard layer reduces the overall toughness benefit. The recommended 2:1 ratio represents an empirically validated balance that should serve as a starting point for process development in similar applications.
The study also highlights an important practical consideration: the manufacturing complexity of layered laminar cladding is significantly higher than monolithic cladding, requiring multiple wire changes, parameter adjustments, and quality checkpoints. However, the performance benefits—particularly in applications involving combined loading modes—often justify the additional processing cost when evaluated on a lifecycle cost basis.
From a standards perspective, the layered laminar approach presents challenges for qualification and acceptance criteria. Traditional cladding standards assume homogeneous overlay layers, and the acceptance of layered structures may require specific qualification procedures. Engineers working with this technology should develop project-specific qualification plans that address the unique characteristics of the layered microstructure, including interface bonding strength, interfacial toughness, and layer-to-layer property gradients.