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

Literature Overview

The paper by Wang Liyue, Han Bingyin, and Wang Xiaoping (2013), published in Hot Working Technology, investigates the influence of two cooling methods—water cooling and air cooling—on the mechanical properties of wear-resistant surfacing plates. The study compares the dilution rate, deposition rate, deformation, and resulting mechanical properties of surfacing plates produced under each cooling condition. This research is directly relevant to manufacturers and engineers involved in the production of wear-resistant components for mining, cement, and material handling equipment.

Core Technical Content

Comparison of Cooling Methods

The study identifies two primary cooling approaches used in the surfacing of wear-resistant plates:

Parameter	Water-Cooled Surfacing	Air-Cooled Surfacing
Cooling method	Active water cooling of substrate	Natural air cooling
Welding parameters	Large welding parameters (high current, high voltage)	Moderate welding parameters
Deposition rate	High	Lower
Substrate deformation	Small	Larger
Base metal dilution rate	Higher	Lower
Fusion zone composition	Higher alloy content, higher carbon	Lower alloy content, lower carbon
Post-weld mechanical properties	Reduced due to rapid quenching	Generally superior
Surfacing layer integrity	Susceptible to local spalling under impact	Better adhesion and integrity
Service life	Shorter due to spalling and delamination	Longer due to better mechanical properties

Dilution Rate and Its Effects

The dilution rate—the fraction of base metal incorporated into the surfacing weld metal—is a critical parameter that significantly influences the mechanical properties of the surfacing layer. In water-cooled surfacing, the large welding parameters required to overcome the cooling effect of water result in a higher dilution rate. This has several consequences:

Alloy dilution: The base metal (typically a carbon steel) dilutes the high-alloy surfacing metal, reducing the concentration of alloying elements that provide wear resistance.
Carbon enrichment: The fusion zone between the surfacing layer and the base metal often contains higher carbon content due to the interaction between the surfacing alloy and the carbon steel substrate. This high-carbon region is susceptible to brittle phase formation and reduced toughness.
Microstructural brittleness: Rapid quenching of the high-carbon fusion zone results in hard but brittle microstructures that are prone to cracking and spalling under impact loading.

Mechanical Property Outcomes

The study demonstrates that air-cooled surfacing plates exhibit superior overall mechanical properties compared to water-cooled surfacing plates:

Hardness: Water-cooled surfacing may achieve higher as-deposited hardness due to rapid quenching, but this hardness is not sustained under service conditions due to spalling.
Toughness: Air-cooled surfacing layers exhibit better toughness due to lower dilution rates and more favorable microstructures.
Impact resistance: Water-cooled surfacing layers are susceptible to local spalling under impact loading, which is a critical failure mode in many wear applications.
Wear resistance in service: Despite potentially lower as-deposited hardness, air-cooled surfacing layers demonstrate better wear resistance in service due to their superior integrity and adhesion.

Deformation and Process Efficiency

Water cooling offers the advantage of reduced substrate deformation, which is beneficial for maintaining dimensional accuracy in precision applications. However, this benefit is offset by the degraded mechanical properties of the surfacing layer. Air cooling, while resulting in greater substrate deformation, produces surfacing layers with better mechanical properties and longer service life.

Engineering Practice Integration

The findings of this study have significant implications for the manufacturing and specification of wear-resistant surfacing plates:

Cooling method selection: Engineers should carefully evaluate the trade-offs between water cooling and air cooling based on the specific application requirements. For applications where wear resistance and impact resistance are paramount (e.g., crusher liners, conveyor components), air cooling is generally preferred. For applications where dimensional accuracy is critical and wear severity is moderate, water cooling may be acceptable.
Dilution rate control: Regardless of the cooling method employed, dilution rate must be controlled to ensure adequate alloy content in the surfacing layer. This can be achieved through:

Optimizing welding parameters (lower current, higher travel speed)
Using surfacing procedures that minimize base metal penetration
Employing multi-pass surfacing with the first pass designed to establish a low-dilution dilution layer

Post-weld treatment: Air-cooled surfacing plates may require stress-relief annealing to reduce welding-induced residual stresses and substrate deformation. This treatment should be performed at a temperature that does not compromise the hardness and wear resistance of the surfacing layer.
Inspection and quality assurance: Wear-resistant surfacing plates should be inspected for adhesion quality, hardness uniformity, and absence of surface defects. Bond strength testing (e.g., bend test, peel test) should be performed to verify the integrity of the surfacing layer-substrate interface.

Key Reflections and Study Insights

This paper presents a clear and practical comparison of two cooling methods for wear-resistant surfacing plate production. The finding that water cooling, despite its advantages in terms of deposition rate and substrate deformation control, results in inferior surfacing layer performance is a valuable insight for manufacturing engineers.

The study also highlights an important principle in surfacing technology: the mechanical properties of the surfacing layer are determined not only by the composition of the surfacing alloy but also by the dilution rate and cooling conditions. Two surfacing layers produced with the same filler metal but under different cooling conditions can exhibit significantly different mechanical properties and service performance.

One area where the study could be expanded is the quantitative characterization of dilution rate as a function of welding parameters and cooling method. Providing specific dilution rate values (e.g., 20% for water cooling vs. 10% for air cooling) would enable engineers to make more precise design decisions. Additionally, the study would benefit from service life data comparing water-cooled and air-cooled surfacing plates in actual wear applications.

The work is a useful reference for manufacturing engineers and procurement professionals involved in specifying and evaluating wear-resistant surfacing plates. The clear demonstration of the trade-offs between process efficiency and product quality underscores the importance of selecting surfacing methods based on service requirements rather than manufacturing convenience alone.