Submerged Arc Automatic Weld Overlay for Cemented Carbide/Steel Bimetallic Composite Materials

1. Definition and Fundamental Principles

Submerged arc automatic weld overlay (SAW overlay) for cemented carbide/steel bimetallic composite materials is a specialized surfacing process in which a hardfacing alloy—typically a tungsten carbide (WC)-based or cobalt-cemented carbide composite—is deposited onto a carbon steel, low-alloy steel, or stainless steel substrate using an automated submerged arc welding machine. The process operates under a granular flux blanket that shields the molten weld pool from atmospheric contamination while simultaneously serving as a thermal insulator and slag-forming agent.

The fundamental metallurgical principle relies on the dilution control between the hardfacing consumable and the base metal. In cemented carbide/steel composites, the overlay layer retains a high volume fraction of undissolved carbide particles (typically WC, TiC, or Cr3C2) within a metallic binder matrix (Co, Ni, or Fe-based), creating a material with hardness values exceeding HRC 70–85 while maintaining adequate toughness at the interface. The automatic nature of the process—driven by constant-voltage or constant-current power sources with mechanized wire feeding and travel speed control—ensures consistent deposition geometry, uniform heat input, and reproducible microstructural characteristics across large production volumes.

The layered structure of the resulting composite consists of three distinct zones: (1) the base steel substrate, (2) a transition/dilution layer where alloying elements from the consumable gradually mix with the base metal, and (3) the functional hardfacing overlay layer rich in carbide particles. Each zone exhibits distinct mechanical and metallurgical properties that must be carefully managed to achieve the target performance envelope.

2. Category and Business Positioning

Within Cladding Technology Shanxi Co., Ltd.'s capability portfolio, submerged arc automatic weld overlay occupies a critical position as a high-productivity surfacing technology that bridges the gap between laboratory-scale hardfacing research and industrial-scale component manufacturing. While the company's three primary technology routes—TIG/MIG weld overlay, hydraulic explosive bonding, and explosion welding—each serve distinct application niches, SAW overlay provides the following strategic advantages:

• High deposition rate: SAW overlay achieves deposition rates of 5–15 kg/h, significantly exceeding TIG (0.5–2 kg/h) and MIG (2–5 kg/h) processes, making it economical for thick overlay layers (3–25 mm) on large components.
• Cost efficiency: The automated nature reduces labor costs and enables unattended operation, lowering the per-unit cost for batch production of wear parts.
• Scalability: The process is inherently suitable for cylindrical, planar, and complex geometric components through multi-axis welding heads and robotic integration.
• Research-to-production pathway: The "learning experience" framework documented in this entry represents a structured knowledge transfer mechanism that converts experimental findings into qualified WPS/PQR packages for customer delivery.

This capability is particularly valuable for customers requiring high-volume production of wear-resistant components—such as mining equipment, cement mill rollers, crusher hammers, and pump impellers—where the combination of high hardness and production throughput is paramount.

3. Technical Purpose and Value Proposition

3.1 Primary Technical Objectives

The development and qualification of submerged arc automatic weld overlay for cemented carbide/steel composites serves several interconnected technical objectives:

1. Wear resistance enhancement: Achieving surface hardness of HRC 70+ with controlled carbide particle distribution to resist abrasion, erosion, and adhesive wear in demanding service environments.
2. Base metal preservation: Maintaining the mechanical integrity of the steel substrate by controlling heat input and thermal cycling to prevent excessive softening or residual stress-induced cracking.
3. Interface bonding quality: Ensuring metallurgical bonding at the overlay/base metal interface with minimal dilution (typically 10–30%) and absence of interfacial defects such as cracks, pores, or lack of fusion.
4. Process reproducibility: Establishing parameter windows that produce consistent results across multiple production shifts, operators, and equipment configurations.

3.2 Customer Value Delivered

For end-users, the SAW overlay technology delivers quantifiable value through extended component service life (typically 3–8× improvement over bare steel), reduced unplanned downtime, lower total cost of ownership, and the ability to refurbish worn components rather than replacing them entirely. The structured learning and qualification framework ensures that each new consumable system or application variant is rigorously validated before customer deployment, minimizing field failure risk.

4. Key Process and Implementation Points

4.1 Process Parameters

The following table summarizes typical parameter ranges for submerged arc automatic weld overlay of cemented carbide consumables onto carbon steel substrates:

Parameter	Typical Range	Notes
Welding current	400–800 A	Higher current for thicker deposits; DCEN polarity preferred for flux-cored consumables
Welding voltage	25–38 V	Adjusted for wire diameter and flux type
Travel speed	200–500 mm/min	Lower speed for increased penetration and reduced dilution
Wire diameter	1.6–3.2 mm	1.6–2.0 mm for multi-layer builds; 2.5–3.2 mm for single-pass thick deposits
Heat input	1.5–4.0 kJ/mm	Lower heat input preserves carbide integrity; monitor for base metal dilution
Flux coverage	5–10 mm thickness	Uniform flux blanket critical for atmospheric protection and slag formation
Preheat temperature	100–300°C	Dependent on base metal carbon equivalent and section thickness
Interpass temperature	150–400°C	Controlled to prevent cracking in transition layers
Number of layers	1–6 passes	Transition layer(s) followed by functional overlay layer(s)
Deposition rate	5–15 kg/h	Process advantage over TIG/MIG for thick overlay requirements

4.2 Multi-Layer Weld Strategy

A critical implementation point in cemented carbide/steel SAW overlay is the multi-layer strategy designed to manage the metallurgical incompatibility between the hardfacing alloy and the steel substrate:

1. Layer 1 – Transition layer: A nickel-based or austenitic stainless steel consumable (e.g., Ni-6, Ni-8, or 309L equivalent) is deposited first to create a ductile buffer zone that accommodates differential thermal expansion and reduces residual stress. Dilution is typically 20–35% in this layer.
2. Layer 2 – Intermediate layer (if required): A partially alloyed hardfacing consumable with moderate carbide content provides a hardness gradient between the transition layer and the functional overlay.
3. Layers 3–N – Functional overlay: The cemented carbide-containing consumable is deposited in the final passes. Dilution in the first functional pass may be 15–25%, decreasing to 5–15% in subsequent passes as the base for dilution becomes the previous overlay layer.

4.3 Consumable Selection Criteria

The selection of flux-cored wire or solid wire consumables for SAW cemented carbide overlay depends on the following factors:

• Carbide type and size: WC particles (5–50 μm) provide excellent abrasion resistance; TiC offers superior thermal stability; Cr3C2 provides moderate hardness with improved toughness.
• Binder alloy composition: Cobalt-based binders offer the highest wear resistance and thermal stability; nickel-based binders provide better ductility and lower cost; iron-based binders are economical but limited in high-temperature applications.
• Flux compatibility: The flux must provide adequate deoxidation, slag fluidity, and hydrogen exclusion without introducing deleterious alloying elements that could degrade carbide stability.
• Manufacturer specifications: Consumables such as those conforming to AWS A5.21 (for flux-cored hardfacing electrodes) or proprietary specifications from manufacturers such as Stellite, Uniboro, or domestic equivalents must be verified for chemical composition, carbide content, and welding suitability.

4.4 Equipment Configuration

Typical SAW overlay equipment configuration includes:

• Power source: DC constant-voltage (CV) source for flux-cored wire; DC constant-current (CC) for solid wire; rated capacity ≥ 800 A at 40 V.
• Wire feed system: Dual-drive roll feed with 0.1 mm resolution; feed rate synchronized with travel speed.
• Travel mechanism: Gear-rack or stepper-motor driven; linear accuracy ±0.5 mm/m; speed range 100–1000 mm/min.
• Flux system: Pre-heated flux hopper (150–200°C) with recirculating flux recovery and sieving system.
• Positioning and rotation: Rotary table or turntable for cylindrical components; multi-axis CNC for complex geometries.
• Thermal monitoring: Thermocouples for preheat and interpass temperature control; infrared thermography for real-time weld pool monitoring (advanced configurations).

5. Applicable Standards and Acceptance Criteria

5.1 Governing Standards

Standard Number	Title / Scope	Relevance to SAW Overlay
GB/T 13813	Welding consumables for hardfacing	Classification and requirements for hardfacing electrodes including flux-cored types
GB/T 19867	Welding procedure specification (WPS)	Format and content requirements for qualified welding procedures
GB/T 3375	Welding terminology	Standardized terminology for overlay and surfacing processes
GB/T 11345	Ultrasonic testing of welds	NDT methods for internal defect detection in overlay layers
GB/T 11346	Magnetic particle testing	Surface and near-surface defect detection
GB/T 12606	Visual examination of welds	Surface quality acceptance criteria for overlay welds
GB/T 10125	Salt spray test	Corrosion resistance evaluation of overlay surfaces (when applicable)
ASTM A5.21	Specification for flux-cored hardfacing electrodes	Consumable qualification and performance requirements
ASTM A5.14	Specification for surfacing electrodes	Electrode classification for overlay applications
ASTM E10 / E18	Rockwell / Brinell hardness test	Hardness verification of overlay layers
ASME Section IX	Qualification of Welding Procedures, Welders, and Welding Operators	WPS/PQR qualification framework for code applications
ISO 14732	Welding procedure specifications – General recommendations	International WPS documentation standards
NACE MR0175	Sour service materials	Requirements when overlay is used in hydrogen sulfide environments

5.2 Acceptance Criteria

The following acceptance criteria apply to SAW overlay of cemented carbide/steel composites:

• Hardness: Overlay layer hardness ≥ HRC 70 (or as specified by the application); hardness gradient from overlay to base metal documented via traverse hardness survey (minimum 10 points across the cross-section).
• Dilution: Maximum dilution in the first functional layer ≤ 30% (verified by optical emission spectrometry or XRF); final overlay layer dilution ≤ 15%.
• Metallurgical bonding: No interfacial cracks, lack of fusion, or excessive carbide segregation at the overlay/base metal interface (verified by metallographic examination per ASTM E3).
• Internal defects: No cracks, pores exceeding 1.5 mm diameter, or slag inclusions exceeding 2 mm in the overlay layer (verified by ultrasonic testing per GB/T 11345 or radiographic testing).
• Surface quality: No surface cracks, undercuts, or excessive reinforcement (max 3 mm for single pass); surface roughness Ra ≤ 25 μm unless otherwise specified.
• Dimensional accuracy: Overlay thickness within ±0.5 mm of nominal; profile uniformity across the component surface.
• Tensile bond strength (adhesive test): Overlay/base metal interface tensile strength ≥ 400 MPa (per ASTM B107 or equivalent method).
• Wear test (when required): Pin-on-disk or dry sand-rubber wheel test demonstrating ≥ 3× wear resistance improvement over bare substrate (per ASTM G99 or ASTM G65).

6. Common Risks and Controls

6.1 Metallurgical Risks

Risk	Cause	Control Measure
Hot cracking in overlay	Excessive sulfur/phosphorus in base metal; high carbon equivalent; rapid solidification	Preheat to 200–300°C; use low-sulfur consumables; control travel speed to moderate cooling rate; post-weld stress relief at 550–650°C
Interfacial cracking	Residual stress concentration; thermal mismatch between overlay and base metal; hydrogen embrittlement	Multi-layer strategy with ductile transition layer; post-weld heat treatment; hydrogen baking at 250°C for 2–4 hours; limit interpass temperature
Carbide dissolution	Excessive heat input; prolonged exposure at high temperature; improper flux chemistry	Limit heat input to ≤ 3.5 kJ/mm; use low-temperature flux; minimize travel speed variation; verify carbide retention via metallography
Excessive dilution	High current/low speed; insufficient root preparation; large gap between passes	Optimize current/speed ratio; use backing bar or root filler; maintain consistent gap (3–5 mm between adjacent passes); monitor via spectroscopic analysis
Base metal softening	Thermal cycling in HAZ; excessive heat input on thin sections	Limit heat input; use backing chill plates; control interpass temperature; consider laser-assisted SAW for heat input reduction

6.2 Process Risks

• Flux contamination: Moisture absorption in flux leads to hydrogen porosity. Control: Store flux at 150–200°C in a heated hopper; limit flux reuse cycles to 3–5 passes; perform loss-on-ignition test periodically.
• Wire feeding irregularity: Uneven wire feed causes spatter, arc instability, and inconsistent bead geometry. Control: Inspect and dress drive rolls weekly; verify feed motor calibration; use new wire spools without surface oxidation.
• Travel speed drift: Speed variation affects heat input and dilution. Control: Calibrate travel mechanism monthly; implement closed-loop speed feedback; monitor bead width as an indirect indicator.
• Flux coverage failure: Inadequate flux blanket exposes the weld pool to atmosphere, causing nitrogen pickup and oxidation. Control: Ensure flux hopper level; verify flux flow rate; inspect coverage on test coupons.

6.3 Quality Assurance Risks

• Inadequate WPS qualification: Using unqualified parameters for production. Control: Complete PQR testing with full mechanical and metallurgical evaluation before production; maintain ASME Section IX or equivalent qualification records.
• Insufficient NDT coverage: Missing internal defects that compromise service life. Control: Implement 100% visual inspection; ultrasonic testing on critical components; destructive coupon testing per production batch.
• Consumable traceability failure: Using wrong consumable batch or expired material. Control: Implement batch traceability system; store consumables with lot numbers; verify chemical composition per batch via OES sampling.

7. Application Scenarios Across Technology Routes

7.1 Positioning Relative to TIG/MIG Weld Overlay

Submerged arc automatic overlay complements the company's TIG/MIG capabilities in the following ways:

• Thick overlay layers (≥ 5 mm): SAW is the preferred process for thick deposits due to its high deposition rate. TIG/MIG are better suited for thin layers (0.5–3 mm) requiring precise control and minimal heat input.
• Large surface areas: For planar or cylindrical surfaces exceeding 500 mm in diameter, SAW automation provides significantly faster coverage. TIG is preferred for complex geometries, tight corners, and small components.
• Batch production: SAW's automation enables unattended operation suitable for production runs of 50–500+ components. TIG/MIG are more flexible for low-volume, high-mix production.
• Hybrid approach: In some applications, a TIG transition layer is applied first for precise interface control, followed by SAW overlay for bulk deposition efficiency.

7.2 Positioning Relative to Hydraulic Explosive Bonding

Hydraulic explosive bonding (water-jet-assisted explosive cladding) produces diffusion-bonded interfaces with zero dilution and excellent metallurgical bonding. SAW overlay differs in the following respects:

• Thickness flexibility: SAW overlay can produce layers from 1 mm to 25+ mm; hydraulic explosive bonding typically produces thinner layers (0.5–5 mm) limited by explosive charge geometry.
• Material compatibility: SAW overlay can deposit any weldable alloy system; hydraulic explosive bonding requires specific material pairs with compatible detonation velocities and impedance matching.
• Interface quality: Hydraulic explosive bonding produces true metallurgical bonds with no intermetallic phases; SAW overlay inherently involves dilution and intermetallic formation at the interface.
• Component size: Hydraulic explosive bonding is limited by charge assembly dimensions; SAW overlay can be applied to any component size that fits on the welding equipment.

7.3 Positioning Relative to Explosion Welding

Explosion welding (air-gap or submerged detonation) produces high-quality bimetallic bonds through high-velocity impact. SAW overlay provides a complementary capability:

• Repair and refurbishment: SAW overlay enables in-situ repair of worn components without requiring the original cladding material or explosive welding infrastructure.
• Functionally graded materials: Multi-layer SAW overlay can create hardness gradients from HRC 60 at the surface to HRC 30 at the interface, providing both wear resistance and toughness.
• Post-weld treatment: SAW overlay can be applied as a surface treatment on explosion-welded components to enhance surface hardness without compromising the base bond.
• Cost-effective prototyping: For new material development, SAW overlay allows rapid screening of hardfacing compositions before committing to expensive explosion welding trials.

7.4 Representative Application Scenarios

1. Mining equipment: Crusher hammers, grinding mill liners, and conveyor chute linings requiring HRC 70+ surface hardness with high production volume.
2. Cement industry: Mill rollers, selector discs, and preheater components subjected to severe abrasive wear from clinker and raw meal.
3. Power generation: Boiler tubes, air preheater elements, and fan blades requiring erosion-resistant overlay in fly ash environments.
4. Petrochemical: Pump impellers, valve seats, and mixing paddles requiring corrosion-resistant and wear-resistant overlay in aggressive fluid environments.
5. Agricultural machinery: Plowshares, harrow discs, and seed metering components requiring economical wear-life extension.
6. Marine and offshore: Propeller trailing edges, thruster nozzles, and intake screens requiring erosion-corrosion resistance.

8. Contribution to Qualification Building and Customer Value

8.1 Qualification Framework Development

The structured "learning experience" documented in this technical entry represents a systematic approach to building the company's qualification infrastructure:

• WPS/PQR packages: Each parameter set developed during the learning phase is documented as a Welding Procedure Specification with supporting Procedure Qualification Records, enabling direct customer submission for code compliance.
• Material qualification matrix: Cross-referencing consumable types (WC-Co, WC-Ni, Cr3C2-Fe, etc.) with substrate types (Q235, 45 steel, 16Mn, 304 stainless, etc.) creates a comprehensive qualification database.
• Performance benchmarking: Standardized testing protocols (hardness traverse, metallographic evaluation, wear testing) establish performance baselines that support customer specification compliance.
• Welder/operator certification: The automated nature of SAW reduces operator skill dependency, but operator qualification for equipment setup, consumable handling, and quality monitoring is maintained per ASME Section IX or ISO 9606.

8.2 Product Delivery Enhancement

• Scalable production: The automated SAW process enables the company to scale from prototype single components to production batches of hundreds of units without proportional increase in labor or cost.
• Consistent quality: Parameter-controlled automation reduces variability, ensuring that every component meets the same hardness, dilution, and defect criteria regardless of production volume.
• Multi-layer customization: The ability to configure different layer sequences and consumable combinations allows the company to tailor overlay specifications to specific customer wear mechanisms and service conditions.
• Integrated quality documentation: Each production batch is accompanied by traceable documentation including WPS reference, consumable lot numbers, NDT reports, hardness survey data, and operator records.

8.3 Customer Value Realization

The submerged arc automatic weld overlay capability delivers measurable customer value through:

1. Extended service life: Typical wear life improvement of 3–8× over unprotected steel components, directly reducing maintenance frequency and spare parts inventory.
2. Cost reduction: Refurbishment of worn components via SAW overlay typically costs 20–40% of new component procurement, with equivalent or superior performance.
3. Rapid turnaround: Automated SAW overlay can process large components (up to 2000 mm diameter) within hours, minimizing equipment downtime for customers.
4. Customization: The ability to vary overlay composition, thickness, and hardness profile enables optimization for specific wear mechanisms (abrasion, erosion, galling, corrosion-abrasion).
5. Technical partnership: The structured learning and qualification approach positions the company as a technical partner rather than a simple processing vendor, providing customers with engineering support for wear management strategies.

9. Continuous Improvement and Technology Roadmap

The "learning experience" framework inherent in this capability entry supports ongoing technology advancement through:

• Process parameter optimization: Systematic DOE (Design of Experiments) studies to refine parameter windows for new consumable systems and substrate combinations.
• Hybrid process development: Integration of SAW with laser cladding for combination of high deposition rate and precise microstructural control.
• In-process monitoring: Implementation of acoustic emission, optical pyrometry, and current/voltage signal analysis for real-time quality feedback and adaptive control.
• Consumable development: Collaboration with consumable manufacturers to develop proprietary flux-cored wires optimized for specific SAW overlay applications.
• Digital transformation: Integration of welding parameter data with MES/QMS systems for full digital traceability and predictive quality analytics.

Through rigorous qualification, systematic documentation, and continuous improvement, the submerged arc automatic weld overlay capability for cemented carbide/steel bimetallic composites represents a core competitive advantage for Cladding Technology Shanxi Co., Ltd., enabling the company to deliver high-performance, cost-effective wear-resistant solutions across diverse industrial sectors.