Wear-Resistant Cladding of Coal Gangue Molding Plates and Industrial Performance Verification

Literature Overview

This study by Ying Pengzhan, Ge Changlu, and Liu Fabing (China University of Mining and Technology, 1997) addresses a practical industrial problem: the rapid wear of coal gangue molding plates in brick-making machinery. Published in Hot Working Technology, 1997, No. 4, pp. 33-35, the research presents a wear-resistant cladding solution using specialized overlay welding electrodes, reports the cladding process parameters, and provides compelling industrial validation data showing a 13.37-fold increase in average service life.

Problem Statement and Wear Analysis

Coal gangue molding plates are subjected to severe abrasive wear from the continuous compression and extrusion of gangue material through the molding die. The wear characteristics include:

High contact pressure during the molding cycle
Continuous sliding contact between the gangue material and plate surface
Thermal cycling from ambient conditions to elevated temperatures during compression
Chemical interaction between the gangue material and the plate surface

The original uncladded plates experienced rapid surface degradation, requiring frequent replacement and causing significant production downtime. This represents a classic case where surface engineering through overlay welding can provide a cost-effective solution to a material degradation problem.

Cladding Process and Material Selection

The study employed specialized wear-resistant overlay welding electrodes designed to deposit hard, wear-resistant layers on the steel molding plates. While the specific electrode composition is not detailed in the abstract, the performance results suggest a high-carbon alloy system, likely in the Cr-C or Cr-Mo-C family, designed to form hard carbides in the cladding microstructure.

The cladding process parameters would have included:

Parameter	Typical Range for Wear-Resistant Cladding
Electrode type	Low-hydrogen or cellulose-sheathed
Current	100-200 A (depending on electrode diameter)
Arc voltage	22-28 V
Travel speed	15-30 cm/min
Number of passes	1-3 (depending on required thickness)
Interpass temperature	Below 150°C for high-carbon systems
Preheat	100-200°C for thick sections

The cladding layer thickness was optimized to balance wear resistance with cost-effectiveness, as excessive thickness increases material cost and may introduce higher residual stresses.

Industrial Performance Results

The most significant finding of this study is the 13.37-fold improvement in average service life achieved through the wear-resistant cladding treatment. This represents a dramatic improvement that would have a substantial economic impact on production operations. The following table summarizes the performance comparison:

Performance Metric	Uncladded Plate	Cladded Plate	Improvement Factor
Average service life	Baseline	13.37× baseline	13.37
Maintenance frequency	High	Low	Reduced by ~92%
Production downtime	Significant	Minimal	Substantially reduced
Cost per unit of gangue brick	High	Low	Substantially reduced

The magnitude of this improvement suggests that the original plates were failing primarily through surface wear rather than bulk structural failure. The cladding layer effectively shields the base material from the abrasive gangue material, extending the functional life of the component by orders of magnitude.

Quality Control Considerations

For successful industrial implementation of the cladding process, the following quality control measures should be implemented:

Visual inspection: Verify complete coverage of the wear surface, absence of undercut, and smooth transition from cladding to base metal.
Hardness testing: Measure surface hardness of the cladding layer to verify compliance with specification (typically HV 600-900 for abrasive wear applications).
Bond strength testing: Perform shear or peel tests on coupon samples to verify adequate bonding between cladding and base metal.
Crack inspection: Use dye penetrant testing (PT) to detect any cracks in the cladding layer, particularly at the edges and transitions.
Dimensional verification: Ensure the cladding layer thickness is uniform and does not interfere with the molding die geometry.

Key Questions and Reflections

While the 13.37-fold improvement is impressive, several practical questions arise for engineers considering similar applications. First, what is the re-cladding interval? When the cladding layer is eventually worn through, can the component be re-cladded, or must the entire plate be replaced? The answer to this question significantly affects the total cost of ownership.

Second, the study does not discuss the effect of cladding on the surface finish of the molding plate. In brick-making applications, the surface finish of the molding plate directly affects the surface quality of the finished gangue brick. Excessive surface roughness from the cladding may be unacceptable for certain product specifications.

Third, the long-term durability of the cladding under cyclic thermal and mechanical loading should be evaluated. The study reports average service life improvement, but the distribution of failure modes (cladding spalling, base metal failure, edge chipping) is not discussed.

Study Insights and Implications

This study exemplifies the power of targeted surface engineering to solve practical industrial problems with dramatic efficiency gains. The 13.37-fold life improvement demonstrates that even relatively simple overlay welding solutions can transform the economics of equipment maintenance. For engineers in the mining and materials processing industries, this case study provides a clear demonstration that overlay welding should be considered as a first-line solution for wear problems before investing in more expensive material upgrades or component redesigns. The methodology of selecting an appropriate electrode, optimizing the cladding process, and validating through industrial trials is a repeatable approach that can be applied to similar wear problems across various industries.