Key Takeaways & Executive Findings
- •• Y2O3 doping up to 0.3 wt.% transforms the Fe45 coating microstructure from columnar to fine cellular/equiaxed grains, enhancing hardness by 14.06% and reducing wear volume by 51.16%. • Excessive Y2O3 (0.9 wt.%) leads to coarser feather-like structures, degrading hardness and wear resistance, yet still outperforming undoped coatings. • Rare-earth oxide modification offers a cost-effective alternative to process optimization for improving laser-clad Fe-based coatings. • The study provides quantitative evidence for optimal Y2O3 content, guiding industrial application for wear-resistant coatings on carbon steel components.
Abstract
The laser-clad Fe45 alloy coating inherently comprises multiple crystalline phases, resulting in a heterogeneous microstructural distribution that influences its performance. In this study, the rare earth yttria (Y2O3) was employed to modify laser-clad Fe45 alloy coatings, and the effects of Y2O3 addition on their microstructure, microhardness, and tribological properties were investigated. As the Y2O3 content increases from 0% to 0.3wt.%, the dominant microstructure transforms from columnar crystals to fine cellular and equiaxed crystals. The modified coating with 0.3wt.% Y2O3 achieves a surface hardness of 568 HV0.3 and a wear volume of 1,735.41 μm3, representing a 14.06% increase in hardness and a 51.16% reduction in wear volume compared to the undoped coating. Further increasing the Y2O3 content from 0.3wt.% to 0.9wt.% gradually leads to the emergence of a coarser feather-like microstructure, characterized by a dendritic framework with inter-dendritic equiaxed crystals. Concurrently, both the hardness and wear resistance of the coating decrease. Nevertheless, all Y2O3-modified coatings surpass the undoped Fe45 coating in both hardness and wear resistance. Appropriate Y2O3 doping effectively refines the Fe45 alloy coating’s microstructure and induces lattice distortion, thereby enhancing its hardness and wear resistance.
1. Introduction
Mechanical transmission components are usually fabricated from carbon steels due to their favorable machinability. However, the inherent limitations of carbon steel in hardness and wear resistance often lead to premature failure from excessive wear [1], significantly compromising service life. To mitigate this issue, metallic wear-resistant coatings are commonly applied to enhance surface durability. Among the various surface modification techniques available, laser cladding technology has gained increasing prominence for engineering applications on carbon steel components.
This preference stems from its distinct advantages, including the production of coatings with finer microstructures, exceptionally narrow heat-affected zones (HAZ), and strong metallurgical bonding to the substrate. These characteristics are generally superior to those achievable by conventional methods such as overlay welding [2], thermal spraying [3], and plasma cladding [4]. Thus, it is increasingly widely used in the engineering field.
Fe-based alloy coatings have been extensively utilized in aerospace, automotive manufacturing, and marine engineering due to their excellent mechanical properties and wear resistance, coupled with lower production costs compared to cobalt- and nickel-based counterparts. Compared to traditional carburizing and nitriding heat treatments for enhancing the wear resistance of carbon steel, the preparation of Fe-based alloy coatings via laser cladding offers simpler processing, higher efficiency, and superior control over coating thickness and hardness. The metallurgical bond formed between the coating and the substrate results in a fusion zone, thus eliminating the risk of spalling caused by abrupt hardness transitions at interfaces between carburized/nitrided layers and the substrate [5-6]. Furthermore, laser cladding technology provides a cost-effective solution for localized repair of worn carbon steel components, making it particularly suitable for on-site remanufacturing of damaged parts. Nevertheless, laser cladding Fe-based coatings usually exhibit microstructural heterogeneities, including mixed morphologies of columnar crystals, dendrites, cellular crystals, and equiaxed grains, often accompanied by microvoids or cracks that significantly degrade coating performance [7-8]. Although process parameter optimization (e.g., laser power, scanning speed, scanning spacing), substrate preheating, and energy field assistance have been proposed to mitigate these defects [9-12], these approaches demonstrate limited effectiveness in microstructure homogenization while being time-consuming, technically challenging, and cost-ineffective.
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Huo-ping Zhao, Li-yao Li, Ming-xue Shen, Qiang Hu, Han-yu Zhou, Ye-long Xiao, De-ying Li, Shao-peng Liu (2026). Microstructure and tribological properties of Y2O3-doped Fe-based alloy coatings by laser cladding. SinoTechIntel Verified Research. https://doi.org/10.1007/s41230-026-5062-0
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Frequently Asked Questions
What is the optimal Y2O3 content for improving the hardness and wear resistance of laser-clad Fe45 alloy coatings?
The optimal Y2O3 content is 0.3 wt.%, which results in a 14.06% increase in hardness and a 51.16% reduction in wear volume compared to the undoped coating.
How does Y2O3 addition affect the microstructure of Fe45 alloy coatings?
Y2O3 addition refines the microstructure, transforming columnar crystals into fine cellular and equiaxed crystals at 0.3 wt.%, but excessive addition (0.9 wt.%) leads to coarser feather-like structures.
Why is laser cladding preferred over conventional surface modification techniques for carbon steel?
Laser cladding produces finer microstructures, narrower heat-affected zones, and stronger metallurgical bonding compared to overlay welding, thermal spraying, and plasma cladding, offering superior coating performance.
What are the main limitations of laser-clad Fe-based coatings without modification?
They exhibit microstructural heterogeneities, including mixed grain morphologies and defects like microvoids and cracks, which degrade coating performance.
How does Y2O3 doping enhance the tribological properties of Fe45 coatings?
Y2O3 doping refines the microstructure and induces lattice distortion, which increases hardness and reduces wear volume, thereby improving tribological performance.
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