Key Takeaways & Executive Findings
- •• Laser cladding successfully fabricated TiC/Ti2AlC core-shell reinforced Ti-based composite coatings, with optimal core-shell structure at 20% Ti2AlC content. • The core-shell structure forms via Al diffusion from Ti2AlC to TiC, enabling in-situ synthesis and avoiding defects like porosity. • The composite coating exhibited significantly improved wear resistance: friction coefficient reduced to 0.342 and wear rate dropped to 47.07% of TC4 substrate. • This work provides a novel approach to design tough, wear-resistant coatings for titanium alloys, leveraging MAX phase decomposition.
Abstract
TiC/Ti2AlC core-shell structure reinforced Ti-based composite coating was prepared by laser cladding technology. The effect of Ti2AlC content on the microstructure and mechanical behavior of the coating was studied. The results showed that the reinforced phase was mainly TiC/Ti2AlC MAX phase core-shell structure at 20% Ti2AlC content. According to the synthesis mechanism, Ti2AlC nucleated on TiC through the diffusion of Al atoms to further generate the core-shell structure. The friction and wear test results showed that the wear resistance of the coating was significantly improved under the load distribution effect of the core-shell structure. The friction coefficient decreased to 0.342, and the wear rate reached 8.19×10−5 mm3/(N·m), which was only 47.07% of TC4 substrate.
1. Introduction
The complexity and variability of the actual working environment of titanium alloy parts further exposes the defects of their surface mechanical properties and aggravates the damage and failure of parts [1, 2]. Surface modification technology can directly and effectively improve the surface performance of titanium alloys to meet service requirements under complex working conditions. To date, component composition systems for coatings on the surface of titanium alloys, such as pure ceramic [3, 4] and pure metal coatings [5, 6], are mostly focused on improving fracture toughness, corrosion oxidation, etc., but the surface strengthening effect on the substrate is poor, its structure is singular, and the interdiffusion effect is limited. Therefore, it is difficult to meet the service requirements when the complex coupling of wear, oxidation and corrosion occurs under actual working conditions.
In contrast, multiphase strengthening in the composite coating can improve the performance and serviceability of the substrate in many aspects [7, 8], and the key to its performance optimization lies in the selection of reinforcements. The reinforcements in particle-reinforced titanium-based coatings, such as TiC, TiSi2, and TiB, are considered the most suitable types of reinforcements due to their similar densities and thermal physical coefficients to titanium alloys. However, the high brittleness determined by the bonding method can easily lead to direct stress failure during service. Therefore, it is necessary to optimize the structure of the reinforcing phase in the composite coating to improve the strength and toughness. As a special organizational structure, the core-shell can play a good role in performance enhancement. LIN et al [9] and WANG et al [10] prepared composite coatings with core-shell structure, whose wear resistance was significantly improved and showed excellent mechanical properties.
However, most of the core-shell preparation methods involve synthesis, and the violent heat release in the reaction causes certain problems, such as powder splashing and high porosity, inside the coating; therefore, it is necessary to adjust the core-shell forming method. Compared with the traditional synthesis method [11, 12], the easy decomposition characteristic of the MAX phase provides a new idea for the formation of a core-shell structure. The above synthetic defects can be effectively avoided by using the escape behavior of A atoms in the new ternary layered cermet MAX phase [13, 14]. Notably, the binary MX phase formed by in situ decomposition has good performance and excellent wettability with the substrate phase, which can achieve high-strength bonding; in this process, the continuous diffusion of A atoms promotes the formation of a core-shell structure [15, 16]. However, the methods for preparing ceramic phases by MAX phase decomposition mostly focus on sintering [17] and plasma spraying [18]. It is difficult to avoid the problems of poor compactness and low efficiency of the coating, and to a certain extent, it is limited by the selection of the functional size of the substrate. As an advanced manufacturing t
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LIU Si-yuan, MO Tai-qian, LIN Bo, WANG Xue-jian, XIAO Hua-qiang, MA Kai (2025). Microstructure evolution and tribological behavior of TiC/Ti2AlC core-shell particle-reinforced composite coatings. Journal of Central South University. https://doi.org/10.1007/s11771-025-6055-7
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Frequently Asked Questions
What is the main objective of this study?
The study aims to fabricate TiC/Ti2AlC core-shell particle-reinforced composite coatings on titanium alloys via laser cladding, and to investigate the effect of Ti2AlC content on microstructure and tribological behavior.
How is the core-shell structure formed?
The core-shell structure forms through the decomposition of Ti2AlC MAX phase, where Al atoms diffuse to TiC, leading to the nucleation of Ti2AlC on TiC and subsequent growth into a core-shell configuration.
What are the key tribological improvements reported?
The composite coating with 20% Ti2AlC content exhibited a friction coefficient of 0.342 and a wear rate of 8.19×10−5 mm3/(N·m), which is only 47.07% of the TC4 substrate, indicating significantly improved wear resistance.
Why is the core-shell structure beneficial for wear resistance?
The core-shell structure provides a load distribution effect, which reduces stress concentration and enhances the toughness and strength of the coating, thereby improving its wear resistance.
What is the significance of using MAX phase decomposition in this context?
Using MAX phase decomposition avoids the violent reactions and defects (like porosity) associated with traditional synthesis methods, offering a more controlled and efficient route to form core-shell reinforced coatings.
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