Powder-Fed Surfacing Method for Manufacturing Wear-Resistant Composite Steel Plates

Literature Overview

This paper, authored by Wang Zhihui, He Dingyong, Zhang Jieze, and Zhou Wenyi from Beijing University of Technology, China Academy of Agricultural Mechanization Sciences, and Tangshan Cement Machinery Factory, was published in Mechanical Engineering Materials in 2001 (Vol. 25, No. 3, pp. 25-27). The study investigates the use of a powder-fed surfacing method (also known as powder arc surfacing or flux-cored arc surfacing with powder addition) for manufacturing wear-resistant composite steel plates. The authors developed specialized surfacing equipment, investigated the effects of surfacing current and powder feed rate on dilution rate, and conducted wear tests on the resulting composite plates. The work is classified under TG455 and represents a practical engineering approach to producing economical wear-resistant components.

Core Technical Findings

The study demonstrates that the powder-fed surfacing method is a practical and feasible approach for manufacturing wear-resistant composite steel plates, with several key findings:

• Deposition efficiency: The deposition efficiency is approximately 1.5 times higher than that of wire-tube surfacing (flux-cored wire surfacing), making it significantly more economical for large-area surfacing applications.
• Dilution rate behavior: At a constant powder feed rate, the dilution rate increases with increasing surfacing current. Increasing the powder feed rate is beneficial for reducing the dilution rate.
• Wear resistance: The wear-resistant composite steel plate exhibits excellent wear resistance, with a relative wear volume 5.5 times lower than that of T10 steel quenched and tempered.
• Fabrication versatility: The composite plates can be conveniently cut and rolled inward, maintaining good formability after surfacing.

Process Analysis and Equipment Development

The powder-fed surfacing method, also known as powder arc welding or powder arc surfacing, involves feeding a flux-cored wire into the arc while simultaneously feeding a separate powder stream into the molten pool. This dual-feed approach allows independent control of the wire composition (which affects weldability and dilution) and the powder composition (which determines the wear layer properties). The authors developed specialized equipment for this purpose, which is a significant practical contribution.

The process parameters that must be carefully controlled include:

1. Surfacing current: Typically in the range of 200-400 A for steel plate surfacing, depending on plate thickness and desired deposition rate. Higher currents increase the deposition rate but also increase dilution, potentially reducing the wear resistance of the overlay.
2. Powder feed rate: Must be balanced against the wire feed rate and arc energy input to achieve the desired dilution rate and wear layer composition. Insufficient powder feed results in excessive dilution and poor wear resistance, while excessive powder feed can lead to porosity and incomplete melting.
3. Travel speed: Affects the heat input per unit length and the geometry of the deposited bead. Higher travel speeds reduce heat input and can reduce dilution, but may also reduce deposition rate.
4. Powder injection angle and distance: The angle and distance at which powder is injected into the arc zone affect the uniformity of powder distribution and the efficiency of powder melting.

Wear Mechanism and Microstructural Analysis

The wear resistance of the composite steel plate is attributed to the high-alloy wear layer deposited on the base steel plate. The wear layer typically contains hard carbide phases (such as cementite Fe3C, M7C3, or M23C6, depending on the powder composition) dispersed in a harder matrix. The wear mechanism in abrasive wear conditions involves:

• Abrasive grooving: Hard abrasive particles plough through the surface, creating material removal through plastic deformation and micro-cutting.
• Adhesive wear: Material transfer between the wear layer and the counterface, which is minimized by the high hardness of the wear layer.
• Fatigue wear: Subsurface crack initiation and propagation due to cyclic loading, which is mitigated by the good toughness of the base steel plate.

The 5.5 times improvement in wear resistance over quenched and tempered T10 steel is substantial and demonstrates the effectiveness of the high-alloy wear layer in resisting abrasive wear. The comparison with T10 steel is particularly relevant because T10 is a commonly used high-carbon tool steel that serves as a benchmark for wear resistance in many industrial applications.

Engineering Practice and Application

The practical applications of wear-resistant composite steel plates produced by powder-fed surfacing are extensive:

• Mining equipment: Conveyor belts, scraper chains, and bucket teeth in mining operations
• Cement industry: Mill liners, hopper linings, and chute linings in cement plants (noted by the involvement of Tangshan Cement Machinery Factory)
• Agricultural machinery: Plowshares, harrow points, and other tillage tools (noted by the involvement of the China Academy of Agricultural Mechanization Sciences)
• Power generation: Coal handling equipment, boiler tubes, and furnace components
• Construction equipment: Excavator buckets, bulldozer blades, and other earthmoving attachments

The ability to cut and roll the composite plates after surfacing is a significant practical advantage, as it allows the plates to be fabricated into complex geometries without compromising the integrity of the wear layer. This versatility makes the powder-fed surfacing method particularly attractive for producing custom-shaped wear-resistant components.

Key Questions and Reflections

Several aspects of this study merit further consideration:

• Long-term wear performance: The laboratory wear tests demonstrate excellent short-term wear resistance, but the long-term performance under actual service conditions, including varying loads, temperatures, and environments, needs to be validated through extended field trials.
• Spallation resistance: A critical concern for composite steel plates is the bond strength between the wear layer and the base plate. Under severe impact or thermal cycling conditions, the wear layer may spall off, rendering the composite plate ineffective. The bond strength should be evaluated through adhesion tests and field trials.
• Microstructural uniformity: The uniformity of the wear layer microstructure across the entire plate surface is important for consistent wear performance. Variations in powder feed rate, travel speed, or arc stability can lead to microstructural variations that affect wear resistance.
• Cost-effectiveness analysis: While the deposition efficiency is 1.5 times higher than wire-tube surfacing, a comprehensive cost analysis including equipment cost, consumable cost, labor cost, and maintenance cost is needed to fully evaluate the economic viability of the powder-fed method.

Summary

This study presents a practical and effective approach to manufacturing wear-resistant composite steel plates using the powder-fed surfacing method. The development of specialized equipment, the systematic investigation of process parameters on dilution rate, and the demonstration of excellent wear resistance (5.5 times better than T10 steel) collectively establish the technical feasibility and economic viability of this approach. The ability to cut and roll the composite plates after surfacing adds significant fabrication flexibility, making this method suitable for a wide range of industrial applications. For practicing engineers, the key takeaway is that the powder-fed surfacing method offers a cost-effective and versatile solution for producing wear-resistant components, provided that process parameters are carefully optimized to achieve the desired dilution rate and wear layer quality.