Search Results (8)

CuCrZr/GH4169 multi-material structures combine the high thermal conductivity of copper alloys with the high strength of nickel-based superalloys, making them suitable for aerospace components that require efficient heat dissipation and high strength. However, additive manufacturing of such dissimilar metals faces challenges, with each laser powder bed fusion (LPBF) and laser directed energy deposition (LDED) process having its limitations. This study employed an LPBF-LDED integrated additive manufacturing (LLIAM) approach to fabricate CuCrZr/GH4169 components. CuCrZr segments were first produced by LPBF, followed by LDED deposition of GH4169 layers using optimized laser parameters. The microstructure, composition, and mechanical properties of the fabricated components were analyzed. Results show a sound metallurgical bond at the CuCrZr/GH4169 interface with minimal porosity and cracks (typical defects at the interface), achieved by exceeding a threshold laser energy density. Elemental interdiffusion forms a 100–200 μm transition zone, with a smooth hardness gradient (97 HV0.2 to 240 HV0.2). Optimized specimens exhibit tensile failure in the CuCrZr region (234 MPa), confirming robust interfacial bonding. These findings demonstrate LLIAM’s feasibility for CuCrZr/GH4169 and underscore the importance of balancing thermal conductivity and mechanical strength in multi-material components. These findings provide guidance for manufacturing aerospace components with both high thermal conductivity and high strength. Full article

To address the critical applications of heterogeneous structures involving nickel-based superalloys (IN718) and copper alloys (CuSn10) under extreme operating conditions, and to address the limitations of traditional joining techniques in terms of interfacial brittleness and geometric constraints, this study employs Laser Powder Bed Fusion (LPBF) technology, specifically multi-material LPBF (MM-LPBF). By precisely melting IN718 and CuSn10 powders layer by layer, the study directly fabricates multi-material IN718/CuSn10 joint specimens, thereby simplifying the complexity of traditional joining processes. The research systematically investigates the interfacial microstructure and mechanical property evolution laws and underlying mechanisms. It reveals that sufficient element diffusion and hardness gradients are present at the IN718/CuSn10 interface, indicating good metallurgical bonding. However, due to significant differences in thermophysical properties, cracks inevitably appear at the interface. Mechanical property tests indicate that the strength of the IN718/CuSn10 joint specimens falls between that of IN718 and CuSn10, but with lower elongation, and fractures primarily occur at the interface. This research provides theoretical support for establishing a process database for LPBF formed of nickel–copper heterogeneous materials, advancing the manufacturing technology of aerospace multi-material components. Full article

In this work, a systematic study was conducted on the fabrication of multi-material components obtained employing Laser-Powder Bed Fusion (L-PBF) technology. The idea of making multi-material components is a winning capability of additive technologies because it allows for the fabrication of Functionally Graded Materials (FGMs) with the customization of parts according to different required properties. This study aims to determine the ability of an inexpensive system, adaptable to the L-PBF machines already on the market, with a powder-spreading technique based on coaters or rollers, to produce parts with continuously variable properties in each layer. Also, the correlation between certain selectable factors in the production design and the result obtained in terms of metallurgical and mechanical properties and chemical composition was investigated. The factors studied were the relative position of the different materials within the powder chamber and the geometry of the equipment designed to produce the cFGMs components. The performed tests involved the use of two materials, a nickel-based superalloy, and a stainless steel, having different chemical, physical, and mechanical properties to obtain gradual property variations in the manufactured samples. Based on the results of post-process characterization obtained via metallographic, chemical, and mechanical analysis, the relative positions of the materials and the geometry of the developed equipment have a limited effect on the sample’s manufactured properties. The characteristics of the FGM zone depend on the nature of the employed powders, and its extent coincides with that defined during the design of the divider. Full article

The nickel-based superalloy, Haynes 230 (H230), is widely used in high-temperature applications, e.g., heat exchangers, because of its excellent high-temperature mechanical properties and corrosion resistance. As of today, H230 is not yet in common use for 3D printing, i.e., metal additive manufacturing (AM), primarily because of its hot cracking tendency under fast solidification. The ability to additively fabricate components in H230 attracts many applications that require the additional advantages leveraged by adopting AM, e.g., higher design complexity and faster prototyping. In this study, we fabricated nearly fully dense H230 in a laser powder bed fusion (L-PBF) process through parameter optimization. The efforts revealed the optimal process space which could guide future fabrication of H230 in various metal powder bed fusion processes. The metallurgical analysis identified the cracking problem, which was resolved by increasing the pre-heat temperature from 80 °C to 200 °C. A finite element simulation suggested that the pre-heat temperature has limited impacts on the maximum stress experienced by each location during solidification. Additionally, the crack morphology and the microstructural features imply that solidification and liquation cracking are the more probable mechanisms. Both the room temperature tensile test and the creep tests under two conditions, (a) 760 °C and 100 MPa and (b) 816 °C and 121 MPa, confirmed that the AM H230 has properties comparable to its wrought counterpart. The fractography showed that the heat treatment (anneal at 1200 °C for 2 h, followed by water quench) balances the strength and the ductility, while the printing defects did not appreciably accelerate part failure. Full article

The laser powder bed fusion (LPBF) is an additive manufacturing technology involving a gradual build-on of layers to form a complete component according to a computer-aided design. The LPBF process boasts of manufacturing value-added parts with higher accuracy and complex geometries for the transport, aviation, energy, and biomedical industries. TiAl-based alloys and high-entropy alloys (HEAs) are two materials envisaged as potential replacements of nickel-based superalloys for high temperature structural applications. The success of these materials hinge on optimization and implementation of tailored microstructures through controlled processing and appropriate alloy manipulations that can promote and stabilize new microstructures. Therefore, it is important to understand the LPBF technique, and its associated microstructure-mechanical property relationships. This paper discusses the metallurgical sintering processes of LPBF, the effects of process parameters on densification, microstructures, and mechanical properties of LPBFed TiAl-based alloys and HEAs. This paper also, presents updates and future studies recommendations on the LPBFed TiAl-based alloys and HEAs. Full article

Titanium aluminides (TiAl) have the potential of substituting nickel-based superalloys (NBSAs) in the aerospace industries owing to their lightweight, good mechanical and oxidation properties. Functional simplicity, control of sintering parameters, exceptional sintering speeds, high reproducibility, consistency and safety are the main benefits of spark plasma sintering (SPS) over conventional methods. Though TiAl exhibit excellent high temperature properties, SPS has been employed to improve on the poor ductility at room temperature. Powder metallurgical processing techniques used to promote the formation of refined, homogeneous and contaminant-free structures, favouring improvements in ductility and other properties are discussed. This article further reviews published work on phase constituents, microstructures, alloy developments and mechanical properties of TiAl alloys produced by SPS. Finally, an overview of challenges in as far as the implementation of TiAl in industries of interest are highlighted. Full article

In this paper, a wet-chemical based method was adopted to acquire the uniform dispersion of graphene nanosheets (GNSs) in a powder metallurgy nickel-based superalloy (FGH96) to fabricate a new GNSs reinforced FGH96 metal matrix composite. The surface of the FGH96 powder was modified using a hydrophilic surfactant named polyvinyl alcohol (PVA), which has good wettability and strong hydrogen bonding between the –OH groups of PVA and oxygen groups of GNSs such as –COOH, –CHO, and –OH. It was shown that the GNSs displayed much better dispersion uniformity on the PVA modified FGH96 powder than the unmodified one. The existence of PVA improved the adsorptive capacity of the GNSs attached on the powder surface and prevented the agglomeration in the following thermal preparation process. Consequently, the micro-hardness of PVA modified composite with 0.1 wt.% GNSs reached 497.9 HV, 3.4% higher than the unmodified FGH96 alloy. Therefore, this preparation process could act as the foundation of a common strategy for the fabrication of GNSs in metal matrix composites with good dispersion uniformity, which may have great potential application in aerospace applications. Full article

As a prospective candidate material for surface coating and repair applications, nickel-based superalloy Inconel 718 (IN718) was deposited on American Iron and Steel Institute (AISI) 4140 alloy steel substrate by laser engineered net shaping (LENS) to investigate the compatibility between two dissimilar materials with a focus on interface bonding and fracture behavior of the hybrid specimens. The results show that the interface between the two dissimilar materials exhibits good metallurgical bonding. Through the tensile test, all the fractures occurred in the as-deposited IN718 section rather than the interface or the substrate, implying that the as-deposited interlayer bond strength is weaker than the interfacial bond strength. From the fractography using scanning electron microscopy (SEM) and energy disperse X-ray spectrometry (EDS), three major factors affecting the tensile fracture failure of the as-deposited part are (i) metallurgical defects such as incompletely melted powder particles, lack-of-fusion porosity, and micropores; (ii) elemental segregation and Laves phase, and (iii) oxide formation. The fracture failure mechanism is a combination of all these factors which are detrimental to the mechanical properties and structural integrity by causing premature fracture failure of the as-deposited IN718. Full article