Application of High-Frequency Surfacing Lining Plates on Feeder Components

Overview of the Study

The research by Wu Zhenqing, Wang Zanbin, and Hou Jiancheng from the School of Materials Science and Engineering at Zhengzhou University (2009) addresses a critical problem in mining machinery: the premature wear failure of feeder components subjected to severe abrasive and impact loading. Feeders in mineral processing plants operate under extreme conditions where material particles, often containing hard rock fragments, repeatedly strike and grind against the structural surfaces. The authors investigated high-frequency induction surfacing (HIFS) as a solution to extend component service life by depositing hard-facing alloy layers onto feeder base plates.

Core Technical Approach

High-frequency induction surfacing operates by using an induction coil to rapidly melt a pre-applied surfacing alloy strip or powder on the substrate surface, creating a metallurgically bonded overlay layer with minimal heat input to the base material. This technique offers several advantages over conventional arc-based surfacing methods for feeder applications:

• Precise thermal control with heat input typically in the range of 0.5 to 2.0 kJ/mm, significantly lower than submerged arc welding (3.0 to 5.0 kJ/mm)
• Rapid cooling rates producing fine microstructures with retained carbide particles
• High deposition efficiency due to the localized melting zone
• Minimal dilution of the overlay alloy, typically maintained below 5 to 10 percent

The surfacing alloys investigated for feeder lining plates typically include high-carbon chromium cast irons (HCCHI) with 2 to 4 percent carbon and 20 to 30 percent chromium, or cobalt-tungsten alloys with 5 to 15 percent tungsten. These compositions produce hard carbide networks (Cr7C3, Cr23C6) or tungsten carbide (WC) dispersions responsible for superior abrasive wear resistance.

Microstructural Analysis and Performance

The induction surfacing process produces a distinct microstructure in the overlay layer consisting of a fine martensitic matrix with evenly distributed hard carbide particles. The rapid solidification rate (typically 10 to 100 K/s at the melt-solid interface) suppresses grain growth and promotes carbide precipitation. Metallographic examination reveals a columnar-to-equiaxed transition in the near-surface region, with the columnar zone extending approximately 0.5 to 1.5 mm from the surface.

The hardness of the surfaced lining plate typically reaches 58 to 65 HRC for high-carbon chromium alloys and 60 to 68 HRC for cobalt-tungsten compositions, compared to 20 to 28 HRC for the carbon steel base material. This hardness gradient provides excellent impact absorption while maintaining surface durability.

Engineering Practice Considerations

In practical feeder applications, several factors must be considered during the surfacing operation. The base material is typically Q345 or 16Mn low-alloy steel, and preheating to 150 to 250 degrees Celsius is recommended to prevent cracking in the heat-affected zone. The surfacing strip or powder must be properly aligned before induction heating, as misalignment leads to uneven layer thickness and reduced bonding strength.

A critical concern is the bond strength between the surfacing layer and the substrate. Insufficient fusion at the interface can result in spalling during service. Post-weld inspection using ultrasonic testing (UT) or magnetic particle inspection (MT) is essential to detect interface defects. The bond strength should exceed 200 MPa to ensure reliable performance under impact loading.

Key Reflections and Insights

This research demonstrates that high-frequency induction surfacing represents a mature and economical solution for feeder lining applications in mining operations. The technique's advantage lies in its ability to combine high surface hardness with a tough substrate, creating a composite structure that resists both abrasive and impact wear. However, the long-term reliability depends heavily on consistent process control, particularly the alignment accuracy and thermal cycle management. Engineers should note that the surfacing layer thickness is typically limited to 1.5 to 3.0 mm per pass, and multiple passes may be required for thicker deposits, each requiring careful inter-pass temperature control to avoid excessive dilution and softening of the previously deposited layer. The economic justification is compelling when considering that a single surfacing operation can extend feeder plate life by 3 to 8 times compared to bare carbon steel, translating to significant downtime reduction in continuous mining operations.