Nickel-Based Overlay Welding Process for Valve Body Sealing Surfaces

Literature Overview

This paper by Lin Lizong, Liu Yichong, Liu Xiaolei, and Zhang Xiaojin from the Department of Mechanical and Power Engineering at East China University of Science and Technology, published in the Welding Journal (Hanjie) in 2006, Issue 4, pages 29–32, presents a nickel-based overlay welding process designed to improve the sealing surface performance of rotary check valves. The study addresses the challenge of achieving uniform and high-quality cladding on three-dimensional curved surfaces, which requires specialized process design and equipment.

Process Design for Three-Dimensional Curved Surfaces

Rotary check valves feature complex three-dimensional curved sealing surfaces that present significant challenges for conventional cladding techniques. The paper describes a GMAW (gas metal arc welding) based cladding process that deposits nickel-based alloy layers uniformly onto the sealing surfaces. The key innovation lies in the design of a specialized welding process strategy and the development of a corresponding execution mechanism and control system that accurately follows the complex surface geometry.

Process Strategy and Equipment Development

The process design involved several critical steps. First, the three-dimensional geometry of the sealing surface was characterized and digitized to establish the trajectory for the welding torch. Second, a specialized execution mechanism was designed to position the welding torch accurately along the curved surface while maintaining a consistent stand-off distance and travel speed. Third, a control system was developed to coordinate the torch movement, wire feed rate, shielding gas flow, and welding current in real time.

The uniformity of the cladding layer on a curved surface is determined by the consistency of the welding parameters throughout the entire trajectory. Any variation in stand-off distance, travel speed, or torch angle can lead to variations in heat input, which directly affects the dilution ratio, microstructure, and mechanical properties of the cladding. The custom control system ensures that these parameters remain within the specified process window, resulting in a uniform and defect-free cladding layer.

Engineering Considerations and Performance Evaluation

The selection of nickel-based alloy for valve sealing surface cladding is driven by the requirements for corrosion resistance, wear resistance, and compatibility with the sealing materials. Nickel-based alloys such as Stellite or Inconel provide excellent resistance to erosion-corrosion and maintain dimensional stability under thermal cycling. The cladding process must also ensure adequate metallurgical bonding with the base material, which is typically a carbon steel or low-alloy steel valve body.

The process qualification and performance evaluation included visual inspection of the cladding surface for uniformity and absence of defects, hardness testing to verify the mechanical properties of the cladding layer, and functional testing of the valve to confirm sealing performance and durability. The successful achievement of all technical indicators confirms that the specialized process and equipment design are effective for this application.

Summary

This paper demonstrates that the application of GMAW-based nickel alloy cladding to three-dimensional curved valve sealing surfaces is achievable through careful process design and specialized equipment development. The custom execution mechanism and control system ensure uniform cladding quality across complex geometries, resulting in improved surface quality and significantly extended valve service life. This work highlights the importance of integrating process engineering with mechanical design in specialized cladding applications.