Wear Resistance of Mining Picks Based on Plasma Cladding Technology

Literature Overview

This 2017 study published in the Journal of North University of China (Natural Science Edition), authored by Cheng Bo, Zhang Yan, Shi Yikun, Dong Lei, and Wang Hongfu from North University of China and Capital Aerospace Machinery Company, investigates the application of plasma transferred arc (PTA) cladding technology to mining picks. Supported by the National Natural Science Foundation of China (Project 21604074), this research addresses the critical need for extending the service life of mining equipment components subjected to extreme abrasive wear.

Core Technical Points

Mining picks are subjected to severe abrasive wear during coal and rock cutting operations. The study evaluates the wear performance of PTA-clad picks compared to conventional manufacturing methods. Key technical aspects include:

Plasma cladding process parameters and their optimization
The microstructure of the cladding layer and its bonding zone
Hardness distribution and gradient characteristics
Abrasive wear testing under simulated mining conditions
Service life comparison with conventional picks

PTA cladding offers several advantages for mining pick applications:

Low dilution rate (typically 5-15%) preserving cladding alloy properties
Excellent bonding strength with minimal heat-affected zone
Ability to clad complex geometries including pick tips
High deposition rate suitable for industrial production

Process Parameters and Microstructure

Parameter	Typical Value	Effect on Cladding Quality
Plasma current	100-200 A	Controls melting rate and dilution
Powder feeding rate	50-150 g/min	Affects layer thickness and porosity
Travel speed	5-15 cm/min	Influences cooling rate and grain size
Shielding gas	Ar (15-25 L/min)	Prevents oxidation of cladding material
Powder composition	Ni-based or Co-based alloy	Determines hardness and wear resistance
Layer thickness	1-3 mm per pass	Controls total cladding thickness

The microstructure of PTA-clad picks typically exhibits a three-zone structure:

Cladding layer: Fine dendritic structure with precipitated carbides (if carbide-containing alloy) or solid solution strengthening
Bonding zone: Narrow transition region with limited base metal dilution
Heat-affected zone: Minimal microstructural change due to low heat input

For Ni-based alloys (such as Stellite 6 or custom compositions), the cladding layer achieves hardness of 400-500 HV with excellent hot hardness retention. For Co-based alloys, hardness reaches 500-600 HV with superior wear resistance at elevated temperatures.

Wear Performance and Service Life

The wear testing typically employs accelerated wear simulation using coal-rock abrasives at representative impact velocities. Results show:

Uncoated picks: Service life of 200-400 meters of cutting
PTA-clad picks (Ni-based): Service life of 800-1500 meters (3-5x improvement)
PTA-clad picks (Co-based): Service life of 1200-2000 meters (5-8x improvement)

The wear mechanism analysis reveals that PTA-clad picks experience primarily abrasive wear with minimal adhesive or fatigue failure. The hard carbide particles (in carbide-reinforced alloys) or solid solution strengthening (in Ni/Co-based alloys) resist material removal effectively.

Engineering Implementation Considerations

For industrial implementation of PTA cladding on mining picks, the following factors must be considered:

Surface preparation: Grind the pick tip to remove scale and oxide; ensure clean, flat surface for powder deposition
Geometry challenges: The conical pick tip requires multi-axis positioning or specialized fixtures for uniform cladding
Thermal management: Apply water cooling to prevent excessive heat input into the pick body
Quality control: Perform hardness testing, microstructure examination, and wear testing on each production batch
Cost analysis: Consider the investment in PTA equipment, powder costs, and labor versus the savings from extended pick life

Common Defects in PTA Cladding

Defect	Cause	Prevention
Porosity	Inadequate shielding, contaminated powder	Use high-purity powder, optimize gas flow
Cracking	High residual stress, incompatible alloy	Apply preheating, select ductile alloy
Uneven thickness	Inconsistent powder feeding	Use calibrated powder feeder, monitor deposition rate
Poor bonding	Surface contamination, low current	Thorough surface preparation, optimize current
Powder spatter	Excessive current, improper nozzle distance	Optimize process parameters, maintain nozzle condition

Study Insights and Practical Implications

This research demonstrates that PTA cladding is a viable technology for enhancing the wear resistance of mining picks. The low dilution rate and excellent bonding strength make it superior to conventional arc welding overlay methods for this application. The ability to clad complex geometries without distortion is particularly advantageous for pick components.

However, the study also highlights challenges in scaling up to industrial production. The relatively slow deposition rate of PTA compared to submerged arc welding requires careful consideration of production throughput. Additionally, the equipment cost and operator skill requirements represent barriers to widespread adoption.

From an engineering perspective, this research supports the development of hybrid manufacturing approaches where PTA cladding is applied to critical wear surfaces while conventional methods handle bulk material deposition. This strategy optimizes both cost and performance for mining equipment applications.