Abstract:Powder metallurgy (PM) technology is an ideal manufacturing process to produce near net shape parts i.e. part that requires little or no machining, examples of PM processes are spark plasma sintering, isostatic pressing and additive manufacturing. PM allows maximisation of materials and produces part with optimised mechanical and physical properties. Also, PM process provides the possibility to further increase the industrial use of PM parts by fabricating it into complex geometrical shapes via joining. Joinin… Show more
Nickel Aluminide intermetallic is a distinctive material for high-temperature applications with remarkable properties. This review article discusses the Nickel Aluminide intermetallic fabricated by various processing techniques like hot pressing, self-propagating high-temperature synthesis, spark plasma sintering, and additive manufacturing. Generally, Nickel Aluminide is blended mostly with chromium, molybdenum, and hafnium reinforcements. These elements increase the tensile property of the base alloy. Mechanical alloying produces nanoparticles with homogeneous distribution for attaining composites with better properties. Nickel Aluminide intermetallic has low ductility and fracture toughness. However, hot pressing improves the ductility and fracture toughness as sintering promotes strengthening mechanisms. In recent years, additive manufacturing has been preferred to build different intermetallic materials.
Nickel Aluminide intermetallic is a distinctive material for high-temperature applications with remarkable properties. This review article discusses the Nickel Aluminide intermetallic fabricated by various processing techniques like hot pressing, self-propagating high-temperature synthesis, spark plasma sintering, and additive manufacturing. Generally, Nickel Aluminide is blended mostly with chromium, molybdenum, and hafnium reinforcements. These elements increase the tensile property of the base alloy. Mechanical alloying produces nanoparticles with homogeneous distribution for attaining composites with better properties. Nickel Aluminide intermetallic has low ductility and fracture toughness. However, hot pressing improves the ductility and fracture toughness as sintering promotes strengthening mechanisms. In recent years, additive manufacturing has been preferred to build different intermetallic materials.
“…Also, the heterogeneity in adding various elements or compounds enables unique porosity, microstructure, and mechanical and tribological characteristics in sintered iron-based components. 8,9 However, the properties of sintered components depend on the base powders and sintering conditions. Fe-based brake pads require secondary matrix and ceramic reinforcements for increased wear resistance and low friction coefficient in heavy-duty applications.…”
The demand for renewable energy has prompted an increasing interest in wind turbine technology, where efficient and reliable brake systems play a critical role in ensuring safety and performance. This study investigates the brazing process to join sintered iron to mild steel for wind turbine brake pad applications. The sintered iron components were synthesized using iron powder with an average particle size of 30 µm and sintered at different temperatures under vacuum and hydrogen environments. Eutectic CuSil with added copper powder was employed as the brazing alloy to join the sintered iron and mild steel. The brazed joints were characterized using various techniques, including optical microscope, scanning electron microscope, energy dispersive X-ray spectroscope, X-ray diffractometer, and microhardness tester. The microhardness of the sintered iron was ∼580 HV for SICV and ∼620 HV for SICH due to oxide formation during processing. The microhardness of the braze joint was 72 HV, and mild steel exhibited 110 HV. Tribological testing was performed to analyze the wear behavior of the sintered iron specimens (before and after the brazing). SICH specimens showed a wear rate of 1.3 × 10−4 g/Nm, and SICV specimens exhibited a wear rate of 5.3 × 10−4 g/Nm. Brazing the sintered iron component (SICV) with mild steel using eutectic CuSil and a modified assembly method in a vacuum successfully achieved a satisfactory joint with improved wear resistance. The study emphasizes the potential of this approach for efficient and reliable brake pad fabrication for wind turbines.
“…Due to complexity of manufacturing processes and diversity of production environments, defects on product surfaces are always various and complex. For example, the manufacturing process of powder metallurgy is composed of casting, forging, rolling, machining, and extrusion, while its porosity, an important characteristic of powder metallurgy sintered materials, is influenced by multiple factors including temperature, sintering time, and pressure [ 4 ]. Surface defects not only directly lower appearance quality, but also reduce product performance and commercial value [ 5 ].…”
Detecting small defects against a complex surface is highly challenging but crucial to ensure product quality in industry sectors. However, in the detection performance of existing methods, there remains a huge gap in the localization and segmentation of small defects with limited sizes and extremely weak feature representation. To address the above issue, this paper presents a weighted matrix decomposition model (WMD) for small defect detection against a complex surface. Firstly, a weighted matrix is constructed based on texture characteristics of RGB channels in the defect image, which aims to improve contrast between defects and the background. Based on the sparse and low-rank characteristics of small defects, the weighted matrix is then decomposed into low-rank and sparse matrices corresponding to the redundant background and defect areas, respectively. Finally, an automatic threshold segmentation method is used to obtain the optimal threshold and accurately segment the defect areas and their edges in the sparse matrix. The experimental results show that the proposed model outperforms state-of-the-art methods under various quantitative evaluation metrics and has broad industrial application prospects.
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