Publications Internationales
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Item Wear Behavior and Microstructure of Thermally Sprayed NiCrBSiFeC and Composite NiCrBSiFeC-WC(Co) Coatings(2021) Abderrahmane, Abderrahmane; Gaceb, Mohamed; Cheikh, Mohammed; Le roux, SabineIn this work, a study was carried out on the friction and wear behavior of flame thermal sprayed NiCrBSiFeC-WC(Co) composite and NiCrBSiFeC coatings subjected to severe wear conditions. For this purpose, flame remelted samples were tested in reciprocating wear conditions based on a cylinder-on-flat configuration. The wear assessment of the coatings was achieved using scanning electron microscopy (SEM) and 3D optical profilometry. The microstructure and the mechanical properties of the coatings were investigated using SEM, EDS and XRD techniques as along with indentation tests. The tribological behavior of the substrate and the coatings was successfully studied thanks to wear tests conducted on an adapted multi test apparatus. The results show that both NiCrBSiFeC and composite coatings induced a significant increase in the steel substrate hardness and wear resistance due to the formation of precipitates with high hardness well dispersed within an ultra-crystalline structure. Besides, adding WC(Co) to NiCrBSiFeC leads to a composite coating with hardness and wear resistance further improved. In return, it increases the coefficient of friction (COF) and the coatings’ roughness. Furthermore, improvements in the surface hardness, the roughness and the coating-substrate adhesion were attained after the remelting process for both NiCrBSiFeC and NiCrBSiFeC-WC(Co) coatings. Wear tracks investigations indicated that reciprocating dry sliding based on cylinder-on-flat test configuration promote several wear mechanisms that may occur simultaneously.Item Characterization and tribological properties of W-Ti-N/Al-Si multilayer surface coating for iron alloy pistons(Springer, 2021) Chemaa, Khaled; Hassani, Salim; Gaceb, MohamedPiston skirts undergo important wear and abrasion due to poor tribological properties. A surface coating system with appropriate friction and hardness properties is proposed in this work to enhance the base material durability of iron alloy pistons. Aluminum-Silicon (Al-Si) thin film was deposited using vacuum evaporation process from 85 at.% Al and 15 at.% Si powders. The W-Ti-N thin film was deposited on the top of the Al-Si thin film using a PVD sputtering process from a W-Ti (70 at.% W and 30 at.% Ti) target onto a stainless steel substrate. The microstructural, mechanical and tribological properties of the multilayer were studied for potential applications on piston skirts manufactured from iron alloys. W-Ti-N/Al-Si multilayer shows a dense microstructure morphology with W2N (200) is the main phase present. Hardness measurements indicate that Al-Si thin film reached a value of 8.8 ± 0.37 GPa, while that of W-Ti-N/Al-Si multilayer reaches values as high as 17.2 ± 0.25 GPa. Tribological tests conducted on the multilayer system revealed interesting results, namely the very low values of the friction coefficient reaching μ ≈ 0.084±0.018 and that of the wear rate showing a value of k <8.7 ± 0.1·10-13 m3/N·m. Results from the present study are promising and provide an good alternative approach toward the reduction of important energy losses related to friction of the iron alloys piston skirtsItem Dissimilar FSW of AA2024 and AA7075 : effect of materials positioning and tool deviation value on microstructure, global and local mechanical behavior(Springer, 2021) Hadji, Idir; Badji, Riad; Gaceb, Mohamed; Cheniti, BillelIn this work, the effect of material location and tool deviation on global and local mechanical behavior of dissimilar AA2024/ AA7075 friction stir weld joints was investigated. The results showed that increasing the tool deviation value up to 1 mm towards the soft material, fixed in the advancing side, improved the material mixing quality and enhanced the grain refine- ment in the stir zone. It was found that the highest ultimate tensile strength was obtained when the AA7075 alloy was fixed in the retreating side for 1-mm tool deviation towards the AA2024 alloy. Above this deviation value, a gradual decrease of the global mechanical properties of the weld joints was noticed. The digital image correlation (DIC) technique coupled to tensile testing revealed an improvement of local strain in the stir zone as well as the heat-affected zones of the dissimilar joints when the AA2024 alloy was positioned in the advancing sideItem Analysis of a Directionally Solidified (DS) GTD-111 Turbine Blade Failure(Springer, 2020) Sabri, Khier; Gaceb, Mohamed; Si-Chaib, Mohamed OualiThe purpose of this paper is to clarify the impact of pitting corrosion and erosion on the directionally solidified (DS) GTD-111 turbine blade behavior. Moreover, the pitting corrosion and oxidation phenomena engendered inside cooling channels of the turbine blade are utterly highlighted. Other features such as the η (Ni3, Ti) platelets nucleation, needle σ-phase precipitation at the interface NiPtAl/(DS) GTD-111 substrate are exhibited as well. Finally, the different microstructural changes in (NiPtAl) coating strata against hot corrosion, oxidation and interaction with (DS) GTD-111 substrate are revealed and argued.Item Lifetime extension prediction of the rejuvenated first stage gas turbine blades(Taylor & Francis, 2019) Sabri, Khier; Ouali Si-Chaib, Mohamed; Gaceb, MohamedThis paper presents a novel method for the first stage gas turbine blades lifetime extension based on degraded GTD-111 substrates hardness evolution after the rejuvenation heat treatments (RHTs) process. Moreover, the RHT impact on directionally solidified (DS) GTD-111 nickel-based suparalloys homogenisation and blades hardness properties were revealed and discussed. The measured hardness values indicate that turbine blades hardness progress is closely related to the nucleation of topologically close packed (TCP) phases, irregular γ’ (Ni3, Al) precipitates growth, and Cr-rich M23C6 Coarsening at grain boundaries. Aspects like γ′/γ eutectic regions rafting, cooling holes oxidation attacks, and formation of cavities within γ-matrix were also identified and analysed.Item Assessment of the degraded high-pressure blades in a land-based gas turbine(Springer, 2021) Sabri, Khier; Si-Chaib, Mohamed Ouali; Gaceb, MohamedThe purpose of this paper is to evaluate high-pressure turbine blades after a long-term thermal exposure in a land-based gas turbine. Emphasis is placed upon structure and composition of the various layers evolving, on the one hand, due to hot oxidation/corrosion attacks and, on the other hand, because of interdiffusion phenomena between the substrates and their protective coatings. This work therefore discusses the influence of γ′-Ni3 (Al, Ti) precipitates coarsening, needle σ-phase nucleation, and M23C6-Carbides formation on the hardness properties of blades. In addition, this assessment attempts to evaluate the influence of γ′-Ni3 (Al, Ti) orientation changes and crystallites size growth on the intrinsic degradation of GTD-111 and IN738LC substratesItem Predictive modelling and optimisation of surface roughness in turning of AISI 1050 steel using polynomial regression(2020) Harhout, Riad; Gaceb, Mohamed; Haddad, Sofiane; Aguib, Salah; Bloul, Benattia; Guebli, AdelhamidAn investigation has been conducted to address the surface integrity optimisation and prediction issue by applying the polynomial regression method for a variety of experiments and cutting conditions. A higher correlation coefficient (R²) was obtained with a cubic regression model, which had a value of0.9480 for Ra. The use of the response surface optimisation and composite desirability show that the optimal set of machining parameters values are (250m/min, 0.2398 mm/rev and 2.3383 mm) for cutting speed, feed and depth of cut, respectively. The optimised surface roughness parameter and productivity are Ra =2.7567 μm and Q = 95.341*103 mm3/ min, respectively. Results show that the models developed can accurately predict the roughness on the basis of measured cutting conditions as input parameters, and can also be used to control the surface roughness by making a comparison between measured and estimated values. Furthermore, operators can benefit from the proposed models if the aim is the reverse determination of the cutting conditions corresponding to the requested roughness profileItem Analysis of a Directionally Solidified (DS) GTD-111 Turbine Blade Failure(Elsevier, 2020) Khier, Sabri; Gaceb, Mohamed; Ouali Si-Chaib, MohamedThe purpose of this paper is to clarify the impact of pitting corrosion and erosion on the directionally solidified (DS) GTD-111 turbine blade behavior. Moreover, the pitting corrosion and oxidation phenomena engendered inside cooling channels of the turbine blade are utterly highlighted. Other features such as the η (Ni3, Ti) platelets nucleation, needle σ-phase precipitation at the interface NiPtAl/(DS) GTD-111 substrate are exhibited as well. Finally, the different microstructural changes in (NiPtAl) coating strata against hot corrosion, oxidation and interaction with (DS) GTD-111 substrate are revealed and arguedItem Effect of Rejuvenation Heat Treatment on the Degraded Turbine Blades(Springer, 2020) Sabri, Khier; Si-Chaib, Mohamed Ouali; Gaceb, MohamedThis paper presents a novel approach to estimate the extended lifetime of first-stage turbine blades made of directionally solidified GTD-111 nickel-based superalloys. These turbine blades were removed from land-based industrial gas turbines for power generation. In addition, this new way to evaluate the lifetime extension of degraded turbine blades after rejuvenation heat treatment is based on knowledge of newly introduced degradation index (Di) evolution. The rejuvenation heat treatment (RHT) process offers an extension of 36% in blades lifetime. Effect of the RHT on the aged γ-γ’ microstructures is presented and discussed.Item Drill string fatigue failure and lockup risks assessment in tortuous trajectory well in Algeria(2017) Belkacem, Lallia; Abdelbaki, Noureddine; Gaceb, Mohamed; Bouali, Elahmoun; Bettayeb, MouradFailure due to fatigue and lock up risks for drilling pipes in tortuous trajectory is a very costly problem in oil and gas industry, since the cyclic loading which occurs while rotating bent drill pipes in a dog leg are more dangerous than rotating buckled drill pipes. This study is aimed to assess these risks and determine whether by integrating 2024 aluminium alloy drill pipes in drilling string, it is possible to extend the drilling operation without having detrimental impact on the drilling string integrity. Accordingly, the obtained results showed that, even though steel drill pipes have better mechanical properties, compared to 2024 aluminium alloy drill pipes, the latter have a better fatigue resistance even in the simultaneous presence of high applied torque and axial load, and severe dog-legs, beside good resistance to wear and corrosion even at high temperature, thereby reducing environmental trash and full consumption in order to minimise pollution