Effect of Surfacing Process on High-Chromium Alloy Powder Surfacing Layer Microstructure and Wear Performance

Literature Overview

This 2013 paper published in Materials for Mechanical Engineering by Liu Yue, Zhang Guoshang, Wei Shizhong, Li Jiwen, and Xu Liujie from Henan University of Science and Technology compares two surfacing processes—wire-powder surfacing and wire-powder-block surfacing—for depositing high-chromium alloy surfacing layers on Q235 carbon steel substrates. Funded by the Henan Provincial Science and Technology Program (112102213117), this research addresses the practical challenge of optimizing surfacing process parameters to maximize wear resistance while maintaining process reliability and economic efficiency.

Process Comparison and Technical Rationale

The two processes compared represent fundamentally different approaches to introducing high-chromium alloy material into the surfacing deposit:

Microstructural Analysis

Phase Composition

Both processes produce surfacing layers with the same fundamental phase composition:

The key microstructural difference between the two processes is the carbide volume fraction and morphology. The wire-powder-block process produces significantly more carbide precipitation due to the higher local chromium concentration achieved when pre-compacted powder blocks melt under the arc. This higher carbide fraction directly translates to enhanced hardness and wear resistance.

Hardness and Wear Performance Comparison

Process Mechanism Analysis

Why Wire-Powder-Block Superiority

The superior performance of the wire-powder-block process can be attributed to several factors:

1. Higher local alloy concentration: Pre-compacted powder blocks maintain high chromium content at the melt zone, whereas loose powder in wire-powder surfacing is partially dispersed by arc plasma and carrier gas, reducing effective alloy concentration.
2. Reduced spatter: The pre-formed block geometry confines the molten material, reducing spatter that would otherwise carry alloying elements away from the deposit. This improves material utilization and maintains the intended composition.
3. Controlled cooling rate: The block geometry provides consistent thermal mass and cooling conditions, producing more uniform microstructure across the surfacing layer.
4. Improved slag management: The compacted block produces denser, more cohesive slag that can be removed more easily, reducing porosity and inclusions in the final deposit.
5. Reduced dilution: The block geometry minimizes base metal dilution compared to loose powder, which tends to spread and mix with the base metal more readily.

FMEA Analysis of Process Risks

Engineering Implementation Guidelines

For production implementation of the wire-powder-block process, the following guidelines should be followed:

1. Block composition: High-chromium alloy powder (Cr 25-30%, C 2-3%, Mo 5-8%, Ni 3-5%) compacted at 1.5-2.0× true density.
2. Block dimensions: 10-20 mm thickness, matched to surfacing bead width for optimal melt geometry.
3. Surface preparation: Substrate ground to Ra < 10 μm with adequate roughening for block adhesion.
4. Process parameters: Arc current 180-220 A, arc voltage 22-28 V, travel speed 80-120 mm/min.
5. Multi-pass strategy: 2-3 passes with interpass temperature control (150-250°C) for thick deposits.
6. Post-weld treatment: Stress relief at 600°C for 2 hours to reduce residual stresses.

Study Insights and Practical Implications

This research demonstrates that process innovation can significantly improve surfacing performance without changing the base alloy composition. The wire-powder-block approach represents a pragmatic engineering solution that addresses multiple quality issues simultaneously—reduced spatter, improved slag removal, enhanced carbide formation, and better process consistency. The improvement in wear resistance (2× base material) and hardness (3× base material) achieved through process optimization alone is remarkable and demonstrates the untapped potential of process-driven quality improvement.

The finding that carbide volume fraction is the primary differentiator between the two processes highlights the importance of maintaining high local alloy concentration during surfacing. This principle extends to other surfacing applications where alloying element retention is critical for achieving target properties. The approach of pre-forming material into controlled geometries before surfacing represents a design philosophy that can be applied to various surfacing scenarios requiring high alloy content in the deposit.

The practical advantages of reduced spatter and improved slag removal have significant economic implications for production operations. Reduced material waste, lower rework rates, and improved process consistency all contribute to cost reduction and quality improvement in industrial surfacing operations.

Reference Value and Outlook

This research provides a clear demonstration that surfacing process design is as important as alloy composition design in achieving optimal performance. The wire-powder-block approach offers a practical, implementable solution for high-chromium alloy surfacing that outperforms conventional wire-powder surfacing across all measured metrics. For engineers developing surfacing specifications and procedures, this work reinforces the principle that process parameters and material form must be considered as integrated design variables rather than independent optimization targets. The methodology of systematic process comparison with comprehensive microstructural and performance characterization provides a template for evaluating alternative surfacing processes in industrial applications.