On the Interface Between LENS® Deposited Stainless Steel 304L Repair Geometry and Cast or Machined Components

Laser Engineered Net Shaping™ (LENS®) is being evaluated for use as a metal component repair/modification process. A component of the evaluation is to better understand the characteristics of the interface between LENS deposited material and the substrate on which it is deposited. A processing and metallurgical evaluation was made on LENS processed material fabricated for component qualification tests. A process parameter evaluation was used to determine optimum build parameters and these parameters were used in the fabrication of tensile test specimens to study the characteristics of the interface between LENS deposited material and several types of substrates. Analyses of the interface included mechanical properties, microstructure, and metallurgical integrity. Test samples were determined for a variety of geometric configurations associated with interfaces between LENS deposited material and both wrought base material or previously deposited LENS material. Thirteen different interface configurations were fabricated for evaluation representing a spectrum of deposition conditions from complete part build, to hybrid substrate-LENS builds, to repair builds for damaged or re-designed housings. Good mechanical properties and full density were observed for all configurations. When tested to failure, fracture occurred by ductile microvoid coalescence. The repair and hybrid interfaces showed the same metallurgical integrity as, and had properties similar to, monolithic LENS deposits.Mechanical Engineerin

Thermal Behavior in the Lens Process

Direct laser metal deposition processing is a promising manufacturing technology which could significantly impact the length oftime between initial concept and finished part. For adoption ofthis technology in the manufacturing environment, further understanding is required to ensure robust components with appropriate properties are routinelyfabricated. This requires a complete understanding ofthe thermal history.during part fabrication and control ofthis behavior. This paper will describe our research to understand the thermal behavior for the Laser Engineered Net Shaping (LENS) process!, where a component is fabricated by focusing a laser beam onto a substrate to create a molten pool in which powder particles are simultaneously injected to build each layer. The substrate is moved beneath the l~ser beam to deposit a thin cross section, thereby creating the desired geometry for each layer. After deposition of each layer, the powder delivery nozzle and focusing lens assembly is incremented in the positive Z-direction, thereby building a three dimensional component layer additively. It is important to control the thermal behavior to reproducibly fabricate parts. The ultimate intent is to monitor the thermal signatures and to incorporate sensors and feedback algorithms to control part fabrication. With appropriate control, the geometric properties (accuracy, surface finish, low warpage) as well as the materials' properties (e.g. strength, ductility) of a component can be dialed into the part through the fabrication parameters. Thermal monitoring techniques will be described, and their particular benefits highlighted. Preliminary details in correlating thermal behavior with processing results will be discussed.Mechanical Engineerin

Dilatometry in the Gleeble: What did you really measure?

The Gleeble is an oft-used tool for welding metallurgy research. Besides producing synthetic weld specimens, it is used to determine phase transformation temperatures and kinetics via dilatometry. Experimental data and an FEM model are used to examine measured dilatation errors because of non-uniform heating of the dilatometer and other sources such as sample elastic and plastic deformation. Both isothermal and constant heating/cooling rate scenarios are considered. Further errors which may be introduced when the dilatation is incorrectly assumed to be linearly related to the volume fraction transformed are also discussed

Assessment of the Precision ID Identity Panel kit on challenging forensic samples

The performance of the Precision ID Identity Panel (Thermo Fisher Scientific) was assessed on a set of 87 forensic samples with different levels of degradation for which a reference sample from the \u201csame donor\u201d or from a \u201cfirst degree relative\u201d was available. PCR-MPS analysis was performed with DNA input ranging from 1 ng to 12 pg and through 21-26 PCR cycles, in replicate tests, and a total number of 255 libraries were sequenced on the Ion Personal Genome Machine\u2122 (PGM\u2122) System. The evaluation of the molecular data allowed to set a fix threshold for locus call at 50 x which suitably worked even when low amounts of degraded DNA (12 pg) were investigated. In these analytical conditions, in fact, 25 PCR cycles allowed the genotyping of about 50% and 35% of the autosomal and the Y-specific markers on average, respectively, for each single amplification with a negligible frequency of drop ins (0.01 %). On the other hand, drop out artefacts reached 18-23% when low copy number and degraded DNA samples were studied, with surviving alleles showing more than 600 reads in 2.9 % of the cases. Our data pointed out that the Precision ID Identity Panel allowed accurate typing of almost any amount of good quality/moderately degraded DNA samples, in duplicate tests. The analysis of low copy number DNAs evidenced that the same allele of a heterozygous genotype could be lost twice, thus suggesting that a third amplification could be useful for a correct genotype assignment in these peculiar cases. Using the consensus approach, a limited number of genotyping errors were computed and about 37% of the autosomal markers was finally typed with a corresponding combined random match probability of at least 1.6 x 10-13, which can be considered an excellent result for this kind of challenging samples. In the end, the results presented in this study emphasize the crucial role of the expert opinion in the correct evaluation of artefacts arising from PCR-MPS technology that could potentially lead to genetic mistyping

Development of a Weldable Neutron Absorbing Structural Material

The National Spent Nuclear Fuel Program, located at the Idaho National Laboratory, coordinates and integrates national efforts in management and disposal of U.S. Department of Energy (DOE)-owned spent nuclear fuel. These management functions include development of standardized systems for packaging, storage, treatment, transport, and long-term disposal in the proposed Yucca Mountain Repository. Nuclear criticality control measures are needed in these systems to avoid restrictive fissile loading limits because of the enrichment and total quantity of fissile material in some types of the DOE spent nuclear fuel. This paper will outline the results to date of a metallurgical development program that is investigating the alloying of gadolinium into a nickel-chromium-molybdenum alloy matrix. Gadolinium has been chosen as the neutron absorption alloying element due to its high thermal neutron absorption cross section and low solubility in the expected repository environment. The nickel-chromium-molybdenum alloy family was chosen for its known corrosion performance, mechanical properties, and weldability. The workflow of this program includes chemical composition definition, primary melting and secondary refining studies, ingot conversion process evaluations, mechanical/physical properties and corrosion testing, welding studies, and national consensus codes, and standards work

Analysis of the antibiotic resistance profiles in methicillin-sensitive s. Aureus pathotypes isolated on a commercial rabbit farm in Italy

The breeding of meat rabbits is an important sector in the livestock industry in Italy. The focus of this study was to describe the antibiotic resistance profile distribution among the Methicillin-sensitive Staphylococcus aureus isolated in a rabbit farm. From 400 animals of different ages and three farm workers, 96 randomly selected strains isolated from various anatomical sites and lesions were analysed. According to spa typing and the resistance profiles towards veterinary and human antibiotics, 26 pathotypes were identified. The highest resistance was observed against Tetracyclines (92.3%) and Macrolides (80.8%), while almost all were susceptible to Penicillins, according to the limited use of β-lactams on the farm. In total, 92.3% of pathotypes were multidrug resistant (MDRs). Two MDR pathotypes belonging to the t2802 spa type were isolated from both farmers and rabbits. Age categories harboured significantly different pathotypes (p = 0.019), while no association was found between pathotypes and lesions (p = 0.128) or sampling sites (p = 0.491). The antibiotic resistance was observed to increase with the time spent in the farm environment (age category). The selective pressure exerted by antibiotic use acted by giving advantage to more resistant strains rather than by lowering susceptibility to various drug categories within strains

Austenite Formation Kinetics During Rapid Heating in a Microalloyed Steel

The model parameters for the normalized 1054V1 material were compared to parameters previously generated for 1026 steel, and the transformation behavior was relatively consistent. Validation of the model predictions by heating into the austenite plus undissolved ferrite phase field and rapidly quenching resulted in reasonable predictions when compared to the measured volume fractions from optical metallography. The hot rolled 1054V1 material, which had a much coarser grain size and a non-equilibrium volume fraction of pearlite, had significantly different model parameters and the on heating transformation behavior of this material was less predictable with the established model. The differences in behavior is consistent with conventional wisdom that normalized micro-structure produce a more consistent response to processing, and it reinforces the need for additional work in this area