Percorrer por autor "Yang, Junfeng"
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- Enhancement on the hardness and oxidation resistance property of TiN/Ag composite films for high temperature applications by addition of SiPublication . Ju, Hongbo; Xu, Luyao; Luan, Jing; Geng, Yaoxiang; Xu, Junhua; Yu, Lihua; Yang, Junfeng; Fernandes, FilipeTitanium nitride and silver (TiN/Ag) composite films exhibited the excellent self-lubricating properties in a wide temperature range due to the formation of the Ag rich tribolayer in the contact. However, Ag addition usually reduces the hardness and oxidation resistance properties of the films. In this paper, TiN/Ag/Si3N4 composite films were deposited using RF magnetron co-sputtering system to improve the mechanical and oxidation resistance properties of the TiN/Ag film. XRD and TEM analysis revealed that three-phases could be identified on the TiN/Ag/Si3N4 films: face-centered cubic (fcc) TiN, fcc-Ag and amorphous Si3N4 phases. The hardness of the TiN/ Ag film increased from ~16 GPa to ~24 GPa for TiN/Ag/Si3N4 with 15.3 at.% of Si due to the formation of the nanocomposite structure. The addition of Si allowed a significant improvement on the oxidation resistance temperature, and effectively avoiding of Ag diffusion, and thereby contributing the stability of the hardness of the film after annealing treatment.
- Multilayer Mo2N-Ag/SiNx films for demanding applications: Morphology, structure and temperature-cycling tribological propertiesPublication . Ju, Hongbo; Zhou, Rui; Luan, Jing; Yu, Lihua; Xu, Junhua; Zuo, Bin; Yang, Junfeng; Geng, Yaoxiang; Zhao, Lijun; Fernandes, FilipeNowadays there is the need to avoid the excessive consumption of liquid lubricant oils, as they are harmful to the environment and hard to disposal. Self-lubricant films have been seen as the sustainable solution to achieve a long-term lubrication under high temperature-cycling conditions. In this manuscript, multilayer Mo2N-Ag/SiNx films with a fixed modulation ratio (thickness of Mo2N-Ag to SiNx) of 3:1, with changing modulation period (Λ, thickness of Mo2N-Ag and SiNx) from 8 to 200 nm were produced to achieve an effective balance between the lubricious phase diffusion control and the adequate formation of the low friction tribo-layers. Results showed that a dual-phase of fcc-Mo2N and fcc-Ag co-existed in Mo2N-Ag layers, while the SiNx layer exhibited an amorphous character. Both room temperature (RT) lubricant and wear-resistance properties of the films were improved by increasing Λ from 8 to 64 nm, while a further increase of Λ degraded the wear-resistance properties. The multilayer film at Λ = 64 nm exhibited an excellent RT-500 °C temperature-cycling tribological properties. Mechanical properties and the synergistic effect of both modulation layers were the cause for the improvement of the tribological properties.
- Mutually enhanced mechanical and tribological properties in magnetron sputtered Mo2N/Ag-SiNx self-lubricating multilayered films via epitaxial growth designPublication . Fernandes, Filipe; Luan, Jing; Wang, Lei; Dong, Songtao; Choukourov, Andrei; Yang, Junfeng; Kalin, Mitjan; Cavaleiro, Albano; Ju, Hongbo; Vincenzini, P.Achieving simultaneous enhancement of both mechanical and self-lubricating properties by incorporating soft lubricants into nitride films has been a longstanding challenge in the development of solid lubricant materials. This paper introduced a novel approach to overcome this challenge by developing coherent-structured Mo2N/Ag-SiNx multilayered films using radio frequency (RF) magnetron sputtering. The multilayer films were designed with a fixed modulation period of 30 nm, while the modulation ratio (γ) was varied from 1:9 to 1:1. The Mo2N layers exhibited a single fcc-Mo2N phase, while the Ag-SiNx layers formed a dual-phase structure comprising fcc-Ag nanoparticles embedded in an amorphous SiNx matrix. At a modulation ratio of 1:9, the Ag-SiNx layer epitaxially grew on the Mo2N template, resulting in a coherent structure. This coherent structure significantly enhanced both the hardness and elastic modulus, reaching approximately 36 GPa and 230 GPa, respectively. The improved wear resistance at room temperature can be attributed to the coherent strengthening effect, which not only elevated the film's hardness but also eliminated sharp interfaces between modulation layers, thereby reducing crack initiation sites. In temperature-cycling tribo-testing from room temperature to 600 °C, the film with a γ of 1:9 maintained a stable coefficient of friction around 0.2, except during the initial room temperature, where it was 0.4. The wear rate could not be accurately calculated due to the adhered tribolayer on the top of the wear track following the initial tribo-test at 600 °C. The excellent tribological properties across temperature cycles were attributed to the synergistic lubricant characteristics of both layers and the formation of self-lubricating tribo-phases. The optimized Mo2N/Ag-SiNx multilayered films provide an effective balance of lubrication and mechanical stability under extreme conditions, making them highly promising for high-performance engineering applications.
- Tribological performance under different environments of Ti—C—N composite films for marine wear-resistant partsPublication . Ju, Hongbo; Zhou, Rui; Luan, Jing; Kumar, Ch Sateesh; Yu, Lihua; Xu, Junhua; Yang, Junfeng; Zhang, Bowei; Fernandes, FilipeThe need for reducing the wear in mechanical parts used in the industry makes self-lubricant films one of the sustainable solutions to achieve long-term protection under different environmental conditions. The purpose of this work is to study the influence of C additions on the tribological behavior of a magnetron-sputtered TiN film in air, water, and seawater. The results show that the addition of C into the TiN binary film induced a new amorphous phase, and the films exhibited a dual phase of fcc (face-centered cubic)-TiN and amorphous carbon. The antifriction and wear-resistance properties were enhanced in air and water by adding 19.1at% C. However, a further increase in the C concentration improved anti-frictional properties but also led to higher wear rates. Although the amorphous phase induced microbatteries and accelerated the corrosion of TiN phases in seawater, the negative abrasion state was detected for all Ti–C–N films due to the adhesion of the tribocorrosion debris on the wear track.