Disc springs are conical annular discs, which are characterized by a high spring force with a small spring travel and good space utilization. In operation, they must meet high demands on the stability of the spring characteristic and the fatigue strength. Under loading, tensile stresses occur which limit the possible applications of disc springs. Compressive stresses can be generated in the stressed areas by means of shot-peening in order to extend the operating limits for a given yield and fatigue strength. Since the spring geometry and characteristics change during shot-peening, the design of the shot-peening treatment is iterative and cumbersome. The present research proposes an incremental forming process for forming and integrated targeted adjustment of residual stresses in disc springs from metastable austenitic stainless steel (MASS), to achieve improved spring properties and high cyclic strength. The main mechanism of residual stress generation is the transformation of metastable austenite into martensite under the action of the forming tool. Different experimental characterization techniques like the hole drilling method, X-ray diffraction, disc compression tests, optical microscopy and cyclic tests are used to correlate the residual stresses and disc spring properties. A numerical model is developed for simulating the martensite transformation in disc springs manufacturing. The results prove that incremental forming enables process-integrated engineering of the desired compressive residual stresses, entailing a higher spring force of metastable austenitic disc springs in comparison to conventional disc springs. Due to martensite formation, the generated residual stresses are stable under cyclic loading, which is not the case for conventionally manufactured springs.

Advanced aluminides strengthened with incoherent Laves phase precipitates are promising lightweight and creep-resistant alternatives for high-alloy steels and superalloys for high-temperature critical components up to 750 °C service temperature. A significant issue with manufacturing these aluminides with conventional casting is the strong coarsening tendency of the Laves phase precipitates at elevated temperatures, leading to a significant strength reduction. In this context, the short lifetime of the melt pool in additive manufacturing and its fast solidification and cooling rates promise to consolidate these aluminides with homogeneously distributed fine Laves phase particles without coarsening. The main scientific objective of this work is to exploit the unique characteristics of the laser powder bed fusion (L-PBF) additive manufacturing (AM) process to print dense and crack-free bulk Fe₃Al-1.5Ta samples containing uniformly distributed (Fe, Al)₂Ta Laves phase precipitates. The Fe-25Al-2Ta (at.%) alloy was selected for this work since its creep resistance at 650 °C surpasses the one of the P92 martensitic–ferritic steel (one of the most creep-resistant alloys developed for steam turbine applications). Fundamentals on process–microstructure relationships governing the L-PBF-fabricated builds are provided by a detailed microstructural characterization using X-ray diffractometer (XRD) and ultra-high-resolution scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX) and high-resolution electron backscatter diffraction (EBSD) detectors. Orientation imaging microscopy (OIM) and grain reference orientation deviation (GROD) maps were applied to measure texture and visualize substructures within the grains. The mechanism of voids formation, morphology, and volume fraction as a function of the input energy density was identified. The melting and solidification dynamics led to microstructures with large columnar grains, porosity, and periodic cracks during the printing process. Processing samples at the building temperatures below the brittle-to-ductile transition temperature, BDTT (750 °C), often caused severe macrocracking and delamination. Crack-free samples with densities higher than 99%, some approaching 99.5%, were fabricated from pre-alloyed gas-atomized powders with a combination of high laser power (250–300 W), slow-to-medium scanning speed (500–1000 mm/s), and 800 °C build plate preheating using a 67° rotation scanning strategy. The morphology of the pores in the volume of the samples indicated a relatively sharp transition from spherical geometry for scanning speeds up to 1000 mm/s to crack-like pores for higher values. The ultra-fast cooling during the L-PBF process suppressed D0₃ Fe₃Al-ordering. The Fe₃Al-1.5Ta builds were characterized by B2 FeAl-type order clusters dispersed within a disordered A2 α-(Fe, Al) matrix. Additionally, the (Fe, Al)₂Ta Laves phase (C14–P6₃/mmc) was predominantly formed at the matrix phase grain boundaries and frequently dispersed within the grains. The quantitative EDX analysis of the matrix gave 77.6–77.9 at.% Fe, 21.4–21.7 at.% Al, and 0.6–0.8 at.% Ta, while the composition of the Laves phase was 66.3–67.8 at.% Fe, 8.7–9.8 at.% Al, and 22.4–24.9 at.% Ta, indicating that the Laves phase is considerably enriched in Ta with respect to the matrix. The L-PBF-fabricated alloys were characterized by coarse, columnar grains which grow epitaxially from the substrate, were several m in width, and extended across several layers along the building direction. The grains exhibited a relatively strong microtexture close to with respect to the building direction. The L-PBF builds showed a bulk hardness value comparable to the as-cast and spark plasma-sintered counterparts. A negligible variation of the hardness across the build height was observed. Within the framework of this study, we demonstrated that the porosity and cracking issues could be resolved mainly by controlling the process parameters and preheating the build platform above the BDTT. Nevertheless, alloy modifications and/or post-manufacturing processing are required for microstructure refinement.

The supply chain management plays a crucial role in delivering products from a supplier, through the manufacturer, distributors, and retailers to the targeted customers. The lifecycle of the products can be ended at any stage due to imperfect quality or waste, which are typically not managed well for a good price. This product’s life can be extended and increased with the use of the circular economy for the value addition processes which turn the waste into byproducts, which can be sold with maximum profit. The automobile industry is associated with various other small industries and is very significant for the economy at the local, national, and international levels. However, the industry also requires sustainable development in its supply chain management, gained by introducing the circular economy concept to manage and reduce the generated waste. The consumption of carbon fiber-reinforced composites (CFRCs) in the manufacturing of numerous automotive parts has acquired immense attention this decade, but the process also generates imperfect products (waste). The proposed model is based on a mathematical formulation to manage imperfect production by reworking and recycling, where the former is required to re-add value to the proportion of the rejected parts, and the latter is to recycle the remaining scrap into useful products by using a circular economy. The outsourcing operation is also added to provide an optimal level of inventory and lot sizing for minimizing the total cost of the supply chain management. Data from the automobile part industry are tested to provide the practical implications of the proposed SCM mathematical model. Sensitivity analysis is performed to understand the significance level of the individual parameters affecting the objective function, i.e., the total cost of the SCM. The results show a meaningful insight for the managers to obtain the benefits of the circular economy in multi-stage automobile part production for sustainable and resilient supply chain management.

End-milling operation of steel grade material is a challenging task as it is hard-to-cut material. Proper selection of cutting tools, cutting conditions, and cutting process parameters is important to improve productivity, surface quality, and tool life. Therefore, the present study investigated the end-milling operation of AISI 1522H steel grade under minimum-quantity lubrication (MQL) conditions using a novel blend of vegetable oils, namely canola and olive oil. Cutting process parameters considered were spindle speed (s), feed rate (f), depth of cut (d), width of cut (w), and cutting conditions (c), while responses were average surface roughness (Ra), cutting forces (Fc), tool wear (TW), and material removal rate (MRR). Experimental runs were designed based on the definitive screening design (DSD) method. Analysis of variance (ANOVA) results show that feed rate significantly affects all considered responses. Nonlinear prediction models were developed for each response variable, and their validity was also verified. Finally, multi-response optimization was performed using the combinative distance-based assessment (CODAS) method coupled with criteria importance through inter-criteria correlation (CRITIC). The optimized parameters found were: s = 1200 rpm, f = 320 mm/min, d = 0.6 mm, w = 8 mm, and c = 100 mL/h. Further, it was compared with other existing multi-response optimization methods and induced good results.