Composite Alloy Wetting Surfacing Process for High Wear-Resistant Layers

Literature Overview

This 1995 paper by Bao Ju and Bao Shuhui from the Beijing Graduate Department of North China Electric Power University, published in New Technology and New Process (新技术新工艺), introduces a novel wetting surfacing process using composite alloys. The authors claim that this method represents the optimal approach for fabricating metal layers with exceptional wear resistance, capable of extending the service life of spare parts and molds by several dozen times. The work addresses three interrelated aspects: new material development and compositional research, process parameters, and inspection/analysis methods.

Core Technical Concept

The wetting surfacing process differs fundamentally from conventional arc surfacing in that it relies on the thermodynamic principle of alloy infiltration (wetting) into the molten pool. Unlike traditional surfacing where the filler metal is deposited as a discrete layer, the composite alloy in this process is designed to wet and penetrate the base metal surface at the microstructural level, forming a metallurgically bonded interface with minimal dilution control issues.

The key innovation lies in the composite nature of the alloy system. By incorporating multiple alloying elements with different melting points and wettability characteristics, the process achieves:

Enhanced interfacial bonding strength through controlled wetting angles
Reduced dilution of the base metal by the composite alloy matrix
Improved metallurgical compatibility between the surfacing layer and the substrate
Homogeneous distribution of hard phases throughout the deposited layer

Process Parameters and Technical Considerations

The wetting surfacing process requires careful control of several critical parameters. Based on the principles described in the literature and supplemented by general engineering knowledge of surfacing processes, the following parameters are essential:

Parameter	Typical Range	Influence
Preheating temperature	200–400 °C	Controls base metal thermal expansion and reduces residual stress
Interpass temperature	150–250 °C	Prevents cracking while maintaining wetting capability
Welding current	100–250 A (SMAW)	Determines heat input and dilution ratio
Travel speed	150–350 mm/min	Controls cooling rate and microstructure refinement
Layer thickness per pass	2–5 mm	Balances deposition efficiency with dilution control

The process is particularly suited for applications involving:

Mining equipment components subjected to severe abrasion
Industrial molds experiencing impact and erosion
Pump impellers and valve components in slurry service
Crusher jaws and chutes in mineral processing

Inspection and Quality Control

The authors emphasize the importance of comprehensive inspection and analysis. For wetting surfacing processes, the following quality control measures are critical:

Macroscopic inspection: Verification of surface finish, porosity, and undercut along the weld toe
Metallographic examination: Assessment of the bonding interface between base metal and surfacing layer, including wetting angle measurement
Hardness profiling: Cross-sectional Vickers hardness measurements to confirm uniform distribution of hard phases
Wear testing: Pin-on-disk or dry sand-rubber wheel testing to quantify wear resistance improvement
Impact testing: Charpy V-notch testing to ensure adequate toughness of the surfacing layer

A critical quality concern in wetting surfacing is the potential for incomplete wetting, which manifests as lack of fusion or micro-porosity at the interface. The composite alloy composition must be carefully designed to achieve a wetting angle below 90 degrees on the specific base metal being treated.

Engineering Practice and Applicability

From a practical standpoint, the wetting surfacing process is most advantageous when:

The base metal has low carbon content and good weldability (e.g., low-carbon structural steel)
High wear resistance is required without sacrificing too much toughness
The component geometry allows for multi-pass surfacing with controlled interpass temperatures
Economic considerations favor extending service life over frequent replacement

The claim of extending service life by "several dozen times" should be interpreted with appropriate engineering judgment. In typical applications, life extensions of 3–10 times are more commonly observed, while extreme values may apply to specific wear conditions with favorable loading patterns.

Study Insights and Implications

The wetting surfacing concept presented in this 1995 paper represents an early but significant contribution to the field of advanced surfacing technologies. The fundamental principle of utilizing alloy wetting behavior to achieve superior interfacial bonding remains relevant in modern surfacing practice. Today, this concept has evolved into various forms including:

In-situ composite surfacing with reactive elements
Functionally graded surfacing layers
Multi-layer surfacing systems with tailored dilution profiles
Thermite surfacing and exothermic surfacing processes

The paper's emphasis on material development combined with process optimization reflects a systems engineering approach that is still considered best practice in modern surfacing technology. The integration of compositional design with process parameter control is the hathe writing systemark of successful surfacing technology development.

Reference Value and Outlook

This paper serves as a foundational reference for engineers interested in the principles of alloy wetting in surfacing applications. While the specific alloy compositions and process details may have evolved over the past three decades, the fundamental concepts remain applicable. Modern engineers should view this work as part of the intellectual lineage that led to today's advanced surfacing technologies, including thermal spray, cladding, and multi-material manufacturing. The emphasis on comprehensive inspection and analysis is particularly valuable, reminding practitioners that process development must always be accompanied by rigorous quality verification.