Effect of heat treatment on microstructure and oxidation properties of Inconel 625 processed by LPBF

This paper presents a study of the microstructure evolution due to oxidation exposure of Inconel 625 (IN625) alloy produced by Laser Powder Bed Fusion (LPBF). IN625 is a nickel-based superalloy characterized by good mechanical properties, excellent oxidation, and corrosion resistance from cryogenic temperatures up to 980 °C, allowing its wide use in various harsh environments. In order to enable the application of LPBF IN625 components at high temperatures, the oxidation properties and microstructure of as-built and post-heat treated LPBF IN625 alloy must be carefully investigated. For this reason, an extensive characterization of the oxidation behavior of the alloy in the as-built condition and after solution treatment was performed. For both these conditions, the oxidation treatments were performed at 900 °C up to 96 h. The characterization was performed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and scratch test analysis. The characteristics of the oxide layer and formed phases were investigated. The as-built IN625 state presented greater oxidation resistance compared to the solutionized IN625 one. The latter condition showed a defected oxide layer with the presence of Nb and Ni oxides inside the Cr oxide layer

Effects of the solution and first aging treatment applied to as-built and post-HIP CM247 produced via Laser Powder Bed Fusion (LPBF)

In this work CM247LC, a low weldable Ni-Based alloy, was produced using selective laser melting (SLM). Despite the initial process parameter optimization, the low defect volume fraction was still uncompliant with manufacturing standards. This condition is principally caused by the high γ’ volume fraction which strongly affects the alloy weldability. Nonetheless, a crack free condition was eventually achieved applying a γ’-sub-solvus Hot Isostatic Pressing Cycle (HIP) which lowered the defects fraction down to 0.04%. The HIP cycle also demonstrated to play an important role in the stabilization of the microstructure, considerably limiting the carbides coarsening during the following heat treatment. Apart from the effectiveness of the healing process brought by HIP, the material microstructure still needs an optimization process which will be described along this paper. In fact, the Initial microstructure obtained after the printing process (the as-built condition) as well as the one obtained after HIP (post-HIP) won’t meet the desired requirements. Namely, the dendritic and γ’ free microstructure of the asbuilt material or the one with coarse and disordered particles obtained right after HIP, still need a tailored homogenization process. This paper will show how the combined effect of the solution and first aging treatment will profoundly alter the γ’ precipitation. More specifically, here, a new heat treatment recipe was developed to promote the precipitation of ordered cuboidal primary γ’ so as to improve creep and high temperature fatigue resistance. Moreover, the use of a γ’ super-solvus temperature allowed to achieve a γ’ volume fraction as high as 73% reducing its average size to 520 nm. At the same time, such heat treatment caused a profound alteration of the crystalline structures of the material promoting a general grain coarsening and the formation of equiaxial grain

Role of the chemical homogenization on the microstructural and mechanical evolution of prolonged heat-treated laser powder bed fused Inconel 625

Ni-based superalloy components for high-temperature applications rely on the long term stability of the microstructure and mechanical properties at service temperatures. Nowadays, the production of such types of components is frequently performed via Additive Manufacturing (AM) technologies. Nevertheless, few studies are dedicated to understanding the behavior of AM Ni-based superalloys upon prolonged exposure to high temperatures. This work aims at studying the effect of prolonged thermal exposures on the microstructure and mechanical properties of Inconel 625 processed by laser powder bed fusion. Thermal exposures within the range of 600 °C and 900 °C for 200 h were performed on this material. The as-built and solution annealed Inconel 625 conditions were selected. The solution annealed state implies a complete chemical homogenization, typically recommended for working at high temperatures, whereas the initial as-built state is characterized by segregations and fine dendritic structures. Upon the studied prolonged thermal exposures, the peculiar as-built microstructure formed a higher quantity of phases with smaller dimensions with respect to the solution annealed condition under thermal exposures. The smaller phases of the as-built state resulted in similar mechanical properties evolution under different temperatures. Differently, the prolonged heat-treated solution annealed conditions exhibited more marked mechanical properties variations due to coarser phases

Analisi costo-efficacia di darbepoetina dopo switch da epoietina-beta nei pazienti in emodialisi: studio retrospettivo monocentrico italiano

Darbepoetin (DARB), a human erythropoietin with improved pharmacological parameters (longer half life and a dose-response relationship independent from the route of administration) is a new treatment option for chronic nephropathy-induced anemia that in many Italian dialysis centers is substituting older erythropoietins, mainly due to greater ease of use. At current prices and at the theoretical and recommended 200:1 dose conversion factor, DARB pharmaceutical cost ranges from –9% to +17% of EPO cost. In this monocentric study, real drug consumption and related actual costs of a pre-switch semester with EPO were analysed and compared to the first two post-switch semesters with DARB therapy. Furthermore, erythropoetic response was recorded and related to drug exposition levels, in order to establish a real life EPO:DARB dose conversion factor. In this experience, the conversion factor was estimated in at least 250-280:1, depending on the method adopted for the estimation. The initial dose, chosen on the basis of the recommended conversion factor, induced an excessive erythropoietic response, which was generally followed by a dose reduction and successive titration to target desired Hb levels, generating the spiraliform dose-response curve associated with delayed feed-back mechanisms. The pharmacoeconomical analysis, conducted in the perspective of the public health service, indicated that the choice of substituting DARB for EPO in the treatment of chronic kidney failure-associated anemia is univocally convenient, the former being less costly and more effective

production and characterization of ni and cu composite coatings by electrodeposition reinforced with carbon nanotubes or graphite nanoplatelets

Electrodeposition is well-known as a versatile and economical processing technique to produce metal coatings on conductive substrates. Recently, it has been gaining increasing interest also for the production of tailored composite coatings, containing for instance floropolymers or silicon carbide. A more novel approach concerns the use of carbon nanotubes or even graphene, in the form of graphite nano-platelets. The production of Ni- and Cu-based nanocomposites containing carbon nanoreinforcements was carried out by using standard electrodeposition conditions, but with a particular attention to the dispersion of the nanotubes. The obtained coatings were strong and well adherent to the steel substrate, and presented rather well dispersed carbon nanotubes or graphite nanoplatelets, even if some agglomerates could be present in samples obtained from highly concentrated suspensions. In the case of nickel-based composite coatings, the size of nickel grains was reduced, and pin-on-disc tests demonstrated a significant increase in the life of the coating. In the case of copper-based composite coatings, thermal diffusivity measurements demonstrated that the carbon nanomaterial does not reduce the conductivity of the pure copper coating

Novel diagnostic DNA methylation episignatures expand and refine the epigenetic landscapes of Mendelian disorders

Overlapping clinical phenotypes and an expanding breadth and complexity of genomic associations are a growing challenge in the diagnosis and clinical management of Mendelian disorders. The functional consequences and clinical impacts of genomic variation may involve unique, disorder-specific, genomic DNA methylation episignatures. In this study, we describe 19 novel episignature disorders and compare the findings alongside 38 previously established episignatures for a total of 57 episignatures associated with 65 genetic syndromes. We demonstrate increasing resolution and specificity ranging from protein complex, gene, sub-gene, protein domain, and even single nucleotide-level Mendelian episignatures. We show the power of multiclass modeling to develop highly accurate and disease-specific diagnostic classifiers. This study significantly expands the number and spectrum of disorders with detectable DNA methylation episignatures, improves the clinical diagnostic capabilities through the resolution of unsolved cases and the reclassification of variants of unknown clinical significance, and provides further insight into the molecular etiology of Mendelian conditions

Novel diagnostic DNA methylation episignatures expand and refine the epigenetic landscapes of Mendelian disorders.

Overlapping clinical phenotypes and an expanding breadth and complexity of genomic associations are a growing challenge in the diagnosis and clinical management of Mendelian disorders. The functional consequences and clinical impacts of genomic variation may involve unique, disorder-specific, genomic DNA methylation episignatures. In this study, we describe 19 novel episignature disorders and compare the findings alongside 38 previously established episignatures for a total of 57 episignatures associated with 65 genetic syndromes. We demonstrate increasing resolution and specificity ranging from protein complex, gene, sub-gene, protein domain, and even single nucleotide-level Mendelian episignatures. We show the power of multiclass modeling to develop highly accurate and disease-specific diagnostic classifiers. This study significantly expands the number and spectrum of disorders with detectable DNA methylation episignatures, improves the clinical diagnostic capabilities through the resolution of unsolved cases and the reclassification of variants of unknown clinical significance, and provides further insight into the molecular etiology of Mendelian conditions

Cost-effectiveness analysis of darbepoetin after switch from epoetin-beta in patients on hemodialysis: an Italian single-center retrospective study

Darbepoetin (DARB), a human erythropoietin with improved pharmacological parameters (longer half life and a dose-response relationship independent from the route of administration) is a new treatment option for chronic nephropathy-induced anemia that in many Italian dialysis centers is substituting older erythropoietins, mainly due to greater ease of use. At current prices and at the theoretical and recommended 200:1 dose conversion factor, DARB pharmaceutical cost ranges from –9% to +17% of EPO cost. In this monocentric study, real drug consumption and related actual costs of a pre-switch semester with EPO were analysed and compared to the first two post-switch semesters with DARB therapy. Furthermore, erythropoetic response was recorded and related to drug exposition levels, in order to establish a real life EPO:DARB dose conversion factor. In this experience, the conversion factor was estimated in at least 250-280:1, depending on the method adopted for the estimation. The initial dose, chosen on the basis of the recommended conversion factor, induced an excessive erythropoietic response, which was generally followed by a dose reduction and successive titration to target desired Hb levels, generating the spiraliform dose-response curve associated with delayed feed-back mechanisms. The pharmacoeconomical analysis, conducted in the perspective of the public health service, indicated that the choice of substituting DARB for EPO in the treatment of chronic kidney failure-associated anemia is univocally convenient, the former being less costly and more effective