Evaluation of a Laboratory-Scale Gas-Atomized AlSi10Mg Powder and a Commercial-Grade Counterpart for Laser Powder Bed Fusion Processing

Laser powder bed fusion (LPBF) is an additive manufacturing technology that implies using metal powder as a raw material. The powders suitable for this kind of technology must respect some specific characteristics. Controlled gas atomization and post-processing operations can strongly affect the final properties of the powders, and, as a consequence, the characteristics of the bulk components. In fact, a complete characterization of the powders is mandatory to fully determine their properties. Beyond the most used tests, such as the volume particle size distribution (PSD) and flowability, the PSD number, the Hausner ratio and the oxidation level can give additional information otherwise not detectable. The present work concerns the complete characterization of two AlSi10Mg powders: a commercial-grade gas atomized powder and a laboratory-scale gas atomized counterpart. The laboratory-scale gas atomization allows to better manage the amount of the fine particles and the oxidation level. As a consequence, a higher particle packing can be reached with an increase in the final density and tensile strength of the LPBF bulk samples

Production of Dense Cu-10Sn Part by Laser Powder Bed Fusion with Low Surface Roughness and High Dimensional Accuracy

Tin-bronze alloys with a tin content of at least 10 wt% have excellent mechanical properties, wear resistance, and corrosion resistance. Among these alloys, Cu-10Sn was investigated in this study for production with the laser powder bed fusion process with a 500W Yb:YAG laser. In particular, a design of experiment (DoE) was developed in order to identify the optimal process parameters to obtain full density, low surface roughness, and high dimensional accuracy. Samples were characterized with Archimedes’ method and optical microscopy to determine their final density. It was shown that the first method is fast but not as reliable as the second one. A first mechanical characterization was performed through microhardness tests. Finally, a set of process parameters was identified to produce fully dense samples with low surface roughness and high accuracy. The results showed that the volumetric energy density could represent an approach that is too simplified, therefore limiting the direct correlation with the physical aspects of the process

Cost Effectiveness Analysis of Disease-Modifying Antirheumatic Drugs in Rheumatoid Arthritis. A Systematic Review Literature

The cost effectiveness of treatments that have changed the “natural history” of a chronic progressive disease needs to be evaluated over the long term. Disease-modifying antirheumatic drugs (DMARDs) are the standard treatment of rheumatoid arthritis (RA) and should be started as early as possible. A number of studies have shown that they are effective in improving disease activity and function, and in joint damage. Our review was focused on revision and critical evaluation of the studies including the literature on cost effectiveness of DMARDs (cyclosporine A, sulphasalazine, leflunomide, and methotrexate). The European League Against Rheumatism (EULAR) recommendations showed that traditional DMARDs are cost effective at the time of disease onset. They are less expensive than biological DMARDs and can be useful in controlling disease activity in early RA

The Economic Burden of Biological Therapy in Rheumatoid Arthritis in Clinical Practice: Cost-Effectiveness Analysis of Sub-Cutaneous Anti-TNFα Treatment in Italian Patients:

Rheumatoid arthritis (RA), with a prevalence of 0.46%, is found in about 272,004 patients in Italy. The socioeconomic cost of rheumatoid arthritis in Italy in 2002 has been estimated at €1,600 million. Cost-effectiveness evaluations have been based on the concept that, with treatment, patients will not progress to the next level(s) of disease severity or will take a longer time to progress, thus avoiding or delaying the high costs and low utility associated with more severe disease. Many cost-effective studies have been based on the variation of Health Assessment Questionnaire (HAQ) in clinical trials. The objective of this study is to perform a cost-effective analysis of 86 patients with rheumatoid arthritis in therapy with adalimumab 40 mg every other week and etanercept 50 mg/week for two years in a population of patients observed in clinical practice. The group of patients in therapy with adalimumab had also taken methotrexate, mean dose 12.4±2.5 mg/week (22 patients) or leflunomide 20 mg/day (16 patients). The group of patients in therapy with etanercept had also taken methotrexate, mean dose 11.7±2.6 mg/week (24 patients) or leflunomide 20 mg/day (24 patients). Incremental costs and QALYs (quality adjusted life years) gains are calculated compared with baseline, assuming that without biologic treatment patients would remain at the baseline level through the year. Conversion HAQ scores to utility were based on the Bansback algorithm. The results after two years showed: in the group methotrexate+adalimumab the QALY gained was 0.62±0.15 with a treatment cost of €26,517.62 and a QALY/cost of €42,521.13. In the group methotrexate+etanercept the QALY gained was 0.64±0.26 with a treatment cost of €25,020.96 and a QALY/cost of €39,171.76. The result of using etanercept in association with methotrexate is cost-effectiveness with a QALY gained under the acceptable threshold of €50,000. These are important data for discussion from an economic point of view when we choose a biologic therapy for rheumatoid arthritis in clinical practice

Short Heat Treatments for the F357 Aluminum Alloy Processed by Laser Powder Bed Fusion

Conventionally processed precipitation hardening aluminum alloys are generally treated with T6 heat treatments which are time-consuming and generally optimized for conventionally processed microstructures. Alternatively, parts produced by laser powder bed fusion (L-PBF) are characterized by unique microstructures made of very fine and metastable phases. These peculiar features require specifically optimized heat treatments. This work evaluates the effects of a short T6 heat treatment on L-PBF AlSi7Mg samples. The samples underwent a solution step of 15 min at 540 °C followed by water quenching and subsequently by an artificial aging at 170 °C for 2-8 h. The heat treated samples were characterized from a microstructural and mechanical point of view and compared with both as-built and direct aging (DA) treated samples. The results show that a 15 min solution treatment at 540 °C allows the dissolution of the very fine phases obtained during the L-PBF process; the subsequent heat treatment at 170 °C for 6 h makes it possible to obtain slightly lower tensile properties compared to those of the standard T6. With respect to the DA samples, higher elongation was achieved. These results show that this heat treatment can be of great benefit for the industry

Development and Characterisation of Aluminium Matrix Nanocomposites AlSi10Mg/MgAl2O4 by Laser Powder Bed Fusion

Recently, additive manufacturing techniques have been gaining attention for the fabrication of parts from aluminium alloys to composites. In this work, the processing of an AlSi10Mg based composite reinforced with 0.5% in weight of MgAl2O4 nanoparticles through laser powder bed fusion (LPBF) process is presented. After an initial investigation about the effect of process parameters on the densification levels, the LPBF materials were analysed in terms of microstructure, thermo-mechanical and mechanical properties. The presence of MgAl2O4 nanoparticles involves an increment of the volumetric energy density delivered to the materials, in order to fabricate samples with high densification levels similar to the AlSi10Mg samples. However, the application of different building parameters results in modifying the size of the cellular structures influencing the mechanical properties and therefore, limiting the strengthening effect of the reinforcement

Low-Power Laser Powder Bed Fusion Processing of Scalmalloy®

Among recently developed high-strength and lightweight alloys, the high-performance Scalmalloy(®) certainly stands out for laser powder bed fusion (LPBF) production. The primary goal of this study was to optimize the Scalmalloy(®) LPBF process parameters by setting power values suitable for the use of lab-scale machines. Despite that these LPBF machines are commonly characterized by considerably lower maximum power values (around 100 W) compared to industrial-scale machines (up to 480 W), they are widely used when quick setup and short processing time are needed and a limited amount of powder is available. In order to obtain the optimal process parameters, the influence of volumetric energy density (VED) on the sample porosity, microstructure and mechanical properties was accurately studied. The obtained results reveal the stability of the microstructural and mechanical behaviour of the alloy for VEDs higher than 175 Jmm(−3). In this way, an energy-and-time-saving choice at low VEDs can be taken for the LPBF production of Scalmalloy(®). After identifying the low-power optimized process parameters, the effects of the heat treatment on the microstructural and mechanical properties were investigated. The results prove that low-VED heat-treated samples produced with an LPBF lab-scale machine can achieve outstanding mechanical performance compared with the results of energy-intensive industrial production