5/4/2023 0 Comments Igor pro poissin fitIn certain circumstances, solidification cracking has been eliminated through the development of improved process control and the use of post-deposition techniques such as hot isostatic pressing (HIP). Numerous cracking mechanisms, defined in the Supplementary information Figure S1, are associated with the deposition of high γ′ superalloys including solidification, strain-age and liquation cracking, with strain-age and liquation cracking being the more difficult to control. Whilst low strengthening precipitate fraction superalloys often have better processability, they offer inferior temperature capabilities when compared to alloys that contain higher γ′ volume fractions (> 60 pct) such as CM247LC. There has also been progress in eliminating cracking for superalloys that contain low volume fractions of the γ′ and γ′′ strengthening precipitates (20 to 40 pct) via L-PBF. To address these issues, significant research has been carried out with notable successes in overcoming the complications of residual stress and anisotropy through process control, post-processing regimes and the use of higher-quality precursors. Specifically, the AM of Ni-based superalloys is often associated with stress-induced micro/macro cracking, pronounced texture and microstructural inhomogeneities. ĭespite the advantages of additive techniques, there remain significant challenges with the deposition of high-performance materials, including Ni-based superalloys. Among AM techniques, laser powder bed fusion (L-PBF) has received particular attention from the aerospace industry as it produces components with higher dimensional accuracies that require less post-process machining. Within the aerospace sector, the use of AM is particularly desirable as it can lead to components with reduced weight, as well as highly complex geometries that can be fabricated without the need for fasteners and joints or with intricate cooling channel architectures. These methods are highly versatile, allowing for greater design freedom and near-net-shape production, which can lead to improved component efficiency and reduced material wastage. Over the last decade, there has been a significant uptake of additive manufacturing (AM) methods across a wide range of industrial sectors for the fabrication of metallic components. Compositional modification of CM247LC including removal of Hf, reduction of C and addition of Nb eliminated the segregation zone but these changes were associated with an increased susceptibility to solidification and liquation cracking. Phase and textural changes after each processing step were consistent with previous studies, although an additional Hf-rich and Cr-depleted segregation zone was identified along intercellular boundaries in the as-deposited condition, believed to be associated with the cracking propensity. This study systematically investigates the microstructural evolution of CM247LC manufactured using laser powder bed fusion following multiple post processing treatments. Whilst post-deposition procedures seek to eliminate or minimise cracks, current procedures do not produce a microstructure suitable for service. Currently, significant cracking occurs during deposition of CM247LC components using laser powder bed fusion and during post-processing. Numerous challenges persist with the additive manufacturing of high γ′ containing Ni-based superalloys such as CM247LC.
0 Comments
Leave a Reply. |