Microstructure and Properties of Wear-Resistant Cladding Alloys

Literature Overview

This paper, published in the Journal of Jiamusi University (Natural Science Edition) in 2023 by Han Zhuorui, Li Mingguo, Liu Yunpeng, and Chen Yaru from the School of Materials Science and Engineering at Jiamusi University, presents a comprehensive investigation of the microstructure and properties of wear-resistant cladding alloys. The study examines the relationship between alloy composition, microstructure, and wear resistance for various cladding alloys used in industrial wear protection applications. The research contributes to the ongoing development of high-performance wear-resistant cladding materials that can extend the service life of equipment in mining, construction, agriculture, and heavy industry.

Core Technical Analysis

The study evaluates several wear-resistant cladding alloy systems, including:

High carbon martensitic alloys (C 3-6 percent, Cr 5-10 percent).
Hardfacing alloys with carbide formers (C 4-8 percent, Cr 5-15 percent, Mo 2-5 percent).
Stellite-type alloys (Co-Cr-W or Co-Cr-Mo based).
Ni-based wear-resistant alloys (Ni-Cr-Mo with carbide formers).
Austenitic-carbide alloys (Ni-Cr with high carbon).

Microstructural Characterization

The microstructure of each alloy system was characterized using optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The key microstructural features and their effects on wear resistance are summarized below:

Alloy System	Primary Microstructure	Hard Phases	Hardness (HV)	Wear Resistance
High carbon martensite	Martensite + retained austenite	Cementite (Fe3C)	500-700	Moderate
Cr-Mo carbide alloy	Martensite + M7C3 carbides	Cr7C3, Mo2C	800-1,100	Good
Stellite 6	Austenite + M6C carbides	Cr7C3, W2C	400-500	Excellent
Ni-Cr-Mo alloy	Martensite + M6C carbides	Cr7C3, Mo2C	700-900	Good
Austenitic-carbide	Austenite + M7C3 carbides	Cr7C3, Cr23C6	500-700	Good

The study found that the distribution, morphology, and volume fraction of hard carbide phases are the primary factors controlling wear resistance. Uniformly distributed, fine carbides provide the best wear resistance because they resist abrasive wear without creating stress concentration points that could initiate cracks.

Wear Test Results

The wear resistance was evaluated using dry sliding wear tests against a counterface of Al2O3 ball (10 mm diameter) at loads of 5, 10, and 20 N. The specific wear rate (volume loss per unit load per unit sliding distance) was measured.

Alloy System	Load 5 N (mm3/N.m)	Load 10 N (mm3/N.m)	Load 20 N (mm3/N.m)	Relative Wear Rate
High carbon martensite	0.0008	0.0015	0.0032	1.0
Cr-Mo carbide alloy	0.0004	0.0008	0.0018	0.5
Stellite 6	0.0002	0.0004	0.0009	0.25
Ni-Cr-Mo alloy	0.0005	0.0010	0.0022	0.65
Austenitic-carbide	0.0006	0.0012	0.0025	0.75

The results show that Stellite 6 provides the best wear resistance across all test loads, followed by the Cr-Mo carbide alloy. The high carbon martensitic alloy, while inexpensive and easy to weld, provides only moderate wear resistance.

Engineering Practice Implications

The study provides practical guidance for selecting wear-resistant cladding alloys for specific applications:

Application	Recommended Alloy	Cladding Process	Cladding Thickness
Mining shovel bucket	Cr-Mo carbide alloy	SAW overlay	10-15 mm
Excavator bucket teeth	High carbon martensite	GTAW overlay	5-8 mm
Cement mill liners	Stellite 6	PTA cladding	8-12 mm
Coal handling equipment	Ni-Cr-Mo alloy	ESW overlay	10-20 mm
Agricultural equipment	Austenitic-carbide	SAW overlay	5-10 mm

The selection of cladding process is also critical. Different processes produce different microstructures and dilution levels, which affect the final wear resistance. PTA cladding produces the lowest dilution (typically 5 to 15 percent) and the best preservation of alloy composition, but it is expensive and limited to smaller areas. SAW and ESW overlay welding produce higher dilution (20 to 40 percent) but are suitable for large-area applications at lower cost.

Process-Structure-Property Relationship

Process	Dilution (%)	Cooling Rate (degrees C/s)	Grain Size (micrometers)	Hardness (HV)
PTA	5-15	50-200	10-30	Highest
GTAW	15-25	30-100	20-50	High
SAW	20-35	10-50	30-80	Moderate
ESW	25-40	5-30	50-100	Lower
FCAW	20-35	15-60	30-70	Moderate

Key Questions and Reflections

The study raises important questions about the trade-off between wear resistance and toughness in cladding alloys. High hardness generally correlates with good wear resistance but reduced toughness, which can lead to chipping and spalling under impact loading. The optimal alloy selection must consider both wear and impact resistance, depending on the specific service conditions.

The study also highlights the importance of the dilution effect on cladding performance. High dilution can reduce the effective hard phase content and alter the microstructure, potentially degrading wear resistance. Process selection must balance cost, productivity, and metallurgical quality.

Study Insights

This research provides a valuable reference for engineers selecting wear-resistant cladding alloys for industrial applications. The systematic evaluation of alloy composition, microstructure, and wear properties demonstrates the importance of understanding the process-structure-property relationship in cladding technology. The study also emphasizes that no single alloy is optimal for all applications; the selection must be based on a comprehensive evaluation of service conditions, cost considerations, and fabrication constraints.

The broader implication is that wear-resistant cladding technology continues to evolve, with new alloy compositions and processes offering improved performance. Engineers must stay informed about these developments and be prepared to adopt new materials and processes when they offer significant advantages for their specific applications.