Browsing by Author "Athmani, Moussa"
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- Effect of carburizing time treatment on microstructure and mechanical properties of low alloy gear steelsPublication . Boumediri, Haithem; Touati, Sofiane; Debbah, Younes; Selami, Salim; Chitour, Mourad; Khelifa, Mansouri; Kahaleras, Mohamed said; Boumediri, Khaled; Zemmouri, Amina; Athmani, Moussa; Fernandes, FilipeGas carburizing significantly enhances the surface properties of low-alloy gear steels, resulting in superior micro-hardness, layer thickness, carbon content, and overall mechanical properties. Unlike other thermochemical processes such as nitriding and carbonitriding, which have limitations in core properties and hardening depth, gas carburizing offers unmatched surface hardness, wear resistance, and mechanical strength. This makes it ideal for demanding applications in the automotive, aerospace, and manufacturing industries. In this research, samples were gas-carburized for 4, 6, or 8 h. The results showed significant improvements: micro-hardness increased from approximately 140 HV to over 819 HV, and the surface layer thickness grew by more than 41%, from 1166 μm to 1576 μm. Additionally, the carbon content in the surface layer increased by over 450%, reaching up to 0.94 wt%. Clear correlations were observed between the duration of heating and the mechanical properties. Longer heating times, particularly after 8 h, raised ultimate tensile strength from 427.29 MPa to 778.33 MPa, while simultaneously decreasing elongation from 26.07% to 2.88% and resilience from 180 J cm−2 to 6.66 J cm−2. This optimization not only enhances surface hardness and durability but also improves key mechanical properties such as tensile strength, stiffness, resilience, and overall mechanical performance.
- Insights into the oxidation resistance mechanism and tribological behaviors of multilayered TiSiN/CrVxN hard coatingsPublication . Ju, Hongbo; Athmani, Moussa; Luan, Jing; AL-Rjoub, Abbas; Cavaleiro, Albano; Yaqub, Talha Bin; Chala, Abdelouahad; Ferreira, Fabio; Fernandes, FilipeIn the last decades, vanadium alloyed coatings have been introduced as potential candidates for self-lubrication due to their perfect tribological properties. In this work, the influence of V incorporation on the wear performance and oxidation resistance of TiSiN/CrN film coatings deposited by direct current (DC) reactive magnetron sputtering is investigated. The results show that vanadium incorporation significantly decreases the oxidation resistance of the coatings. In general, two layers are formed during the oxidation process: i) Ti(V)O2 on top, followed by a protective layer, which is subdivided into two layers, Cr2O3 and Si–O. ii) The diffusion of V controls the oxidation of V-containing coatings. The addition of vanadium improves the wear resistance of coatings, and the wear rate decreases with increasing V content in the coatings; however, the friction coefficient is independent of the chemical composition of the coatings. The wear of the V-containing coatings is driven by polishing wear.
- RF magnetron sputtered Nb–V–N composite coatings for high-temperature self-lubricant applicationsPublication . Athmani, Moussa; Kong, FanLin; Ju, Hongbo; Luan, Jing; Zhang, Chengke; Ma, Bingyang; Cavaleiro, Albano; Fernades, Filipe; Fernandes, FilipeEnhancing the tribological properties of hard ceramic coatings for high temperature applications is one of the hot topics in the solid lubricant field. In this paper, a series of Nb–V–N coatings with different V concentrations were deposited using RF magnetron sputtering system, and the crystalline structure, mechanical and tribological properties were investigated. Results showed that the Nb–V–N coatings regardless of V concentrations exhibited two phase fcc-NbN with V in solid solution and hcp-NbN phase. The hardness and elastic modulus of the coatings were enhanced by adding 5.3 at.% of V. The room temperature tribological properties of the coatings were improved by the addition of V well due to the enhanced mechanical properties and the nature excellent self-lubricant characteristics. The evaluation of main tribophase from the wear track at elevated temperatures from the self-lubricant V2O3 at 400 °C to the V2O5 at 800 °C, contributed to the stable and excellent anti-frictional properties of the coating with a V concentration of 12.4 at.%. However, the wear rate of the coatings drops gradually with the increase of V concentrations due to the large amount of soft but lubricant tribophases at elevated temperatures.