Effect of Cooling Methods on Mechanical Properties of Wear-Resistant Surfacing Plates

Literature Overview

This study, published in 2013 in Heat Processing Technology (Vol. 42, No. 23, pp. 185–186), was conducted by Wang Liyue, Han Bingyin, and Wang Xiaoping from Anhui Electromechanical Vocational College and Anhui Conch Kawasaki Energy Saving Equipment Manufacturing Co., Ltd. The research compares the mechanical properties of wear-resistant surfacing plates produced using water cooling and air cooling methods during the welding process, examining the effects of dilution rate, deposition rate, and cooling method on the overall performance of the surfacing plates.

Technical Context and Background

Wear-resistant surfacing plates are widely used in mining, cement, and aggregate processing industries, where equipment components are subjected to severe abrasive wear. The performance of these surfacing plates is determined by the hardness, toughness, and wear resistance of the surfacing layer, which in turn are influenced by the welding process parameters and cooling conditions.

Comparison of Cooling Methods

Parameter	Water Cooling	Air Cooling
Deposition rate	High	Low
Weld distortion	Low	High
Base material dilution rate	High	Low
Fusion zone alloy content	High	Low
Carbon content in fusion zone	High	Low
Cooling rate	Rapid	Moderate
Post-cooling mechanical properties	Reduced	Better
Local spalling under impact	Prone	Less prone
Service life	Shorter	Longer

Technical Analysis

Water Cooling Process Characteristics

Water cooling is employed in large-scale surfacing operations where high deposition rates are required. The process involves:

High heat input: Large welding parameters are used to achieve high deposition rates, which increases the dilution of the base material into the surfacing layer.
Low distortion: The rapid heat extraction by water cooling reduces thermal distortion of the plate.
High dilution: The large heat input and the presence of water cooling lead to significant dilution of the base material into the surfacing layer, resulting in a fusion zone with high alloy content and elevated carbon content.
Rapid cooling: The water cooling provides rapid cooling of the weld zone, which can lead to the formation of hard but brittle microstructures.

Air Cooling Process Characteristics

Air cooling is employed in surfacing operations where mechanical property optimization is prioritized over deposition rate:

Lower heat input: Smaller welding parameters are used, reducing the dilution of the base material.
Higher distortion: The slower heat extraction leads to greater thermal distortion of the plate.
Low dilution: The lower heat input results in minimal dilution of the base material, preserving the composition of the surfacing layer.
Moderate cooling: The air cooling provides moderate cooling rates that allow for the formation of microstructures with balanced hardness and toughness.

Mechanical Property Comparison

The study found that:

Hardness: Water-cooled surfacing plates may exhibit higher hardness due to the rapid cooling, but this hardness is associated with brittleness.
Toughness: Air-cooled surfacing plates exhibit better toughness due to the more favorable microstructure development.
Wear resistance: Air-cooled surfacing plates demonstrate better overall wear resistance due to the combination of adequate hardness and improved toughness.
Impact resistance: Water-cooled surfacing plates are prone to local spalling under impact loading, while air-cooled plates resist spalling better.

Engineering Practice Implications

Process Selection Criteria

The selection of cooling method for wear-resistant surfacing plates should be based on the following criteria:

Criterion	Water Cooling	Air Cooling
Production volume	High volume	Moderate volume
Deposition rate requirement	High	Moderate
Distortion tolerance	Low	Moderate
Mechanical property requirement	Moderate	High
Service life requirement	Short	Long
Cost sensitivity	High	Moderate

Optimization Strategies

To optimize the performance of wear-resistant surfacing plates, the following strategies can be employed:

Hybrid cooling: A combination of water cooling for the initial passes and air cooling for the final passes can provide a balance between deposition rate and mechanical properties.
Inter-pass temperature control: Maintaining appropriate inter-pass temperatures can control the thermal cycle and reduce the negative effects of high heat input.
Welding parameter optimization: Using smaller wire diameter, lower current, and higher travel speed can reduce dilution while maintaining acceptable deposition rates.
Post-weld heat treatment: Stress relief heat treatment can reduce residual stresses and improve toughness, particularly for water-cooled surfacing plates.
Multi-layer surfacing: Using multiple thin layers with controlled inter-pass temperatures can improve the mechanical properties of the surfacing layer.

FMEA Analysis for Surfacing Plate Failure

Failure Mode	Potential Causes	Detection Method	Risk Priority
Local spalling under impact	High carbon in fusion zone, brittle microstructure	Impact testing, visual inspection	High
Cracking in dilution zone	High residual stress, high carbon	MT, PT	High
Wear failure	Insufficient hardness, poor microstructure	Hardness testing, wear testing	Medium
Distortion	Excessive heat input, inadequate fixturing	Dimensional measurement	Medium

Study Insights and Implications

This study provides a clear comparison of the mechanical properties of wear-resistant surfacing plates produced using water cooling and air cooling methods. The finding that air-cooled surfacing plates exhibit better overall mechanical properties, despite the lower deposition rate and higher distortion, is of significant practical importance. It demonstrates that the pursuit of high deposition rates at the expense of mechanical properties can lead to premature failure and reduced service life.

For engineering practice, the key takeaway is that the cooling method used during surfacing has a profound impact on the mechanical properties and service performance of the resulting surfacing plate. Engineers must carefully consider the trade-offs between production efficiency and component performance when selecting the cooling method. In many cases, a compromise approach—such as hybrid cooling or optimized welding parameters—may provide the best balance between deposition rate and mechanical properties.

The study also reinforces the importance of dilution control in surfacing operations. Excessive dilution of the base material into the surfacing layer not only alters the composition of the surfacing layer but also creates a fusion zone with elevated carbon content that is susceptible to cracking and spalling. Process optimization to minimize dilution is essential for producing high-quality wear-resistant surfacing plates.