CLADDING TECHNOLOGY SHANXI CO., LTDWeld Overlay Technology in Manufacturing Engineering
Overview and Context
This 2017 publication in the journal "Manufacturing Technology and Machine Tools" (制造技术与机床) provides a comprehensive review of weld overlay technology as applied to manufacturing engineering. The paper addresses the evolution of overlay welding from simple surface hardening to sophisticated tribological and corrosion-resistant surface engineering, reflecting the maturation of this technology over several decades.
Core Technical Content
The paper surveys multiple overlay welding processes and their application domains:
| Process | Typical Application | Layer Thickness | Dilution Rate |
|---|---|---|---|
| SMAW | General wear/corrosion protection | 2–5 mm per pass | 15–30% |
| SAW | Thick overlay deposits, pipeline repair | 5–10 mm per pass | 10–20% |
| GMAW | Automation, multi-layer builds | 2–4 mm per pass | 10–25% |
| PTA | Precision overlay, aerospace | 0.5–2 mm per pass | 5–15% |
| Laser cladding | High precision, low dilution | 0.1–1 mm per pass | 5–10% |
| Oxy-fuel | Field repair, large surfaces | 1–3 mm per pass | 20–40% |
The paper emphasizes that the selection of overlay process must be guided by the specific service requirements of the component. For components requiring precise dimensional control and low thermal input, such as turbine blades or precision shafts, laser cladding or PTA are preferred. For large structural components such as pump casings or valve bodies where cost efficiency is paramount, SAW or GMAW are more appropriate.
Key Technical Points
Material Selection Philosophy
The paper articulates a systematic approach to overlay material selection based on the tribological conditions:
- Abrasive wear conditions — high-carbon martensitic steels (e.g., D2, M2), cobalt-chromium alloys (Stellite 6), or tungsten carbide-containing composites.
- Adhesive wear conditions — nickel-based alloys (Inconel 625, Monel 400), austenitic stainless steels (309, 310).
- Corrosive environments — duplex stainless steels (2205, 2507), nickel-based alloys (Hastelloy C276, Inconel 718).
- Combined wear and corrosion — Ni-Cr-Mo alloys, certain duplex stainless steels.
Multi-Layer Overlay Design
A critical concept discussed is the multi-layer overlay strategy, where different materials are deposited in sequence to create a graded or composite surface structure. The first layer (bond layer) ensures metallurgical compatibility with the base material, while subsequent layers provide the desired surface properties. For example, a typical three-layer design for a pump impeller might consist of:
- Layer 1 (bond layer): 309 stainless steel, 1–2 mm, ensuring weldability with carbon steel base
- Layer 2 (intermediate layer): 316 or 321 stainless steel, 2–3 mm, providing corrosion resistance
- Layer 3 (surface layer): Ni-Cr-Mo alloy or Stellite, 1–2 mm, providing wear and corrosion resistance
Process Control and Quality Assurance
The paper highlights several quality control measures essential to overlay welding:
- Pre-weld inspection: Surface preparation quality, base material verification, and dimensional accuracy.
- In-process monitoring: Welding parameters (current, voltage, travel speed), interpass temperature, and layer thickness.
- Post-weld inspection: Non-destructive testing (MT, PT, UT), hardness profiling, dilution analysis, and mechanical property testing.
The paper also discusses the importance of dilution control. High dilution rates can compromise the surface properties by incorporating base material elements into the overlay layer, potentially reducing hardness, corrosion resistance, or wear resistance. Process parameters such as wire feed speed, arc length, and gas flow rate must be carefully controlled to minimize dilution.
Study Insights and Reflections
This paper serves as an excellent reference for understanding the breadth and depth of weld overlay technology in modern manufacturing. The systematic approach to process selection, material design, and quality control reflects the maturity of the field. The emphasis on dilution control is particularly important, as it is often the root cause of overlay failures in service.
From a practical standpoint, the paper reinforces the need for welding procedure qualification (WPQ) and welder performance qualification (WPQ) in accordance with standards such as ASME IX or NB/T 47014. The overlay process must be qualified not only for structural integrity but also for the specific surface properties required by the application. This dual requirement — structural soundness and functional surface properties — distinguishes overlay welding from conventional structural welding and requires specialized qualification procedures.