Minimum Dilution Research Articles

ANALYSIS AND EVALUATION OF THE BIOGAS PURIFICATION TECHNOLOGIES FROM H2S

H2S concentrations in biogas are limited by environmental regulations. Because these gases are toxic to human health, cause corrosion, and damage the combined heat and power (CHP) engines and other metallic parts after burning. Hence, the following requirements must be met by a biogas purification method: 1 – high H2S removal efficiency (RE), 2 – stability over a long period of time, 3 – low cost, 4 – minimal biogas dilution, and 5 – straightforward structure. There are various physical, chemical, and biological technologies, which can be undertaken to meet earlier mentioned criteria and efficiently remove H2S from biogas. In this study, electrochemical oxidation, adsorption by zeolite, pressure swing adsorption, adsorption on activated carbon, adsorption on metal oxides, adsorption on nano-particles, metal sulfide precipitation, water scrubbing, membrane separation, organic solvents (amine), microaeration, and purification by sulfur-oxidizing bacteria (anoxic, aerobic, anaerobic), will be introduced, while their pros and cons are compared and discussed in detail.

Experimental investigations on Inconel 718 hard-faced layer deposited over SS304 using cold metal transfer

This study used the cold metal transfer (CMT) process to deposit Inconel 718 (IN718) as a hard-facing layer on the Base Substrate (BS) of 304 stainless steel (SS304). Different profiles like straight/stringer and sinewave weaving techniques are adopted to deposit the hard-faced layers. For the above profile, IN718 is deposited as a single-track and 30 % overlap to study the impact of heat input on the base substrate. Through the Bead on Plate (BoP) trials, optimal parameters of welding current (175 A), speed (15 cm/min), and wire feed rate (7 m/min) is identified. Sinewave beads (single track) explored a minimum dilution of 13.46 % compared to all the combinations. The sinewave distributed the heat uniformly compared to the straight/stringer profile. At the top surface, fine grains with an equiaxed structure are identified. Annealed twins are present at the base substrate, and elongated columnar grains near the interface are identified through EBSD. The sinewave with 30 % overlapped layers exhibited a maximum hardness of 274.4 HV0.5 at the Hard Face Zone (HFZ), whereas the base substrate hardness was 204 HV0.5. Further, the hard-faced samples achieve an ultimate strength of 750 Mpa through the tensile test. The micro-voids, dimples, and riverine structure observed from fractured surfaces witnessed the ductile fracture. The segregation of Niobium is scattered at the inter-dendritic region. The SEM-EDX results confirm the existence of Niobium, Nickel, and Molybdenum elements.

Evaluation of antibacterial activity against Burkholderia pseudomallei VTCC 70157 and cytotoxicity ofpomegranate (Punica granatum) aqueous extract

Melioidosis is a severe acute infectious disease caused by Burkholderia pseudomallei, especially high epidemiological risk factors in agricultural operations with people frequently exposed to soil or water sources containing this bacterium. In this study, the thermal and gastric stability of antimicrobial activity of aqueous extracts prepared from pomegranate (Punica granatum) against Burkholderia pseudomallei VTCC 70157 (NA23) was evaluated by agar plate diffusion, minimal inhibitory dilution (MID), and minimal bactericidal dilution (MBD) methods. Additionally, the cytotoxicity of aqueous extract to HEK293, HepG2, and HT29 cell lines was also studied. The results showed that aqueous extracts of different pomegranate parts had a high antibacterial activity with an antibacterial zone diameter in the range of 21-28 mm. MID and MBD values were under 1:256 and 1:128, respectively. At the extraction temperature of 100oC, antibacterial activities were significantly higher than those of 25 and 70oC. This study also demonstrated that the antibacterial activity of the extracts highly remained under simulated gastrointestinal conditionsexcept for the MID value of the twig extracts which was increased by two times. In addition, the extracts exhibited low cytotoxicity with the tested human cell lines, with ID50 values consistently being remarkably higher than the corresponding MID values. The study results suggest that aqueous extracts of pomegranate prepared by decoction according to traditional medicine might be effective through oral administration for the treatment of melioidosis.

High Spatiotemporal Model-Based Tracking and Environmental Risk-Exposure of Wastewater-Derived Pharmaceuticals across River Networks in Saxony, Germany

Wastewater treatment plants represent relevant point sources of environmental-adverse pharmaceuticals in river systems. Extensive monitoring and substance-routing models are crucial for environmental risk assessment and river planning. However, most current models assume long-term and large spatial averaged values of pharmaceutical consumption and river discharge flows. This study describes a detailed tracking of pharmaceutical occurrence across river networks with high spatiotemporal resolution to assist better environmental risk assessments. Using high spatiotemporal prescription data of four (pseudo-) persistent pharmaceuticals and river discharge characterization, an adjusted graph-theory-based model was implemented to efficiently evaluate the impact of the effluents of 626 wastewater treatment plants across nine river networks located in Saxony, Germany. Multisite calibration results demonstrated the model capability to satisfactorily predict daily pharmaceutical loads and concentrations with high spatial discretization. Based on minimal river dilution and mean predicted concentrations, the risk exposure revealed carbamazepine and ciprofloxacin as the most critical pharmaceuticals and Vereinigte Mulde as the most risk-exposed river network with up to 34.0% and 23.7% of its river length exceeding half and the total of ecotoxicological criteria, respectively. In comparison, other river networks showed less than 23.5% and 15.0% of their river lengths exceeding half and the total of ecotoxicological criteria of all four selected pharmaceuticals, respectively.

Determination of Essential and Non-Essential Elements in Dietary Supplements by Microwave-Induced Plasma Optical Emission Spectrometry: Method Development and Study of Non-Spectral Interferences

Dietary supplements have been used to overcome nutritional deficiencies and the knowledge concerning essential and non-essential elements is an important issue. In this work the suitability of microwave-induced plasma optical emission spectrometry (MIP OES) for the determination of essential and non-essential elements in dietary supplements was evaluated. Twelve dietary supplement samples of several classifications (vitamins/minerals, minerals, amino acids, and botanicals) were digested in their whole form for determination of essential (Ca, Co, Cu, Fe, K, Mg, Mn, Mo, Na, and Zn) and non-essential (Ag, Al, B, Ba, Be, Cd, Cr, La, Li, Ni, Pb, Sr, and V) elements by MIP OES. Potential non-spectral interferences by common concomitants (C, S, K, Na, and Ca) were evaluated, as well as those by residual acidity of digests. The study of non-spectral interferences showed that a signal suppression effect is observed with higher concentrations of Ca, Na, and K. Relatively good robustness was observed considering the presence of C and S, as well as residual HNO3. The limits of quantification (LOQs) were dependent on the sample mass used for decomposition (from 0.6 to 1.6 g in the commercial product) and on the minimum dilution factor. From the results, there was a prevalence of essential and non-essential elements in vitamins and minerals, minerals, and botanicals-based dietary supplements, whereas lower concentrations were found in the dietary supplements based on amino acids. All elements were in a concentration below the recommended dietary allowances (RDAs), exception for those with the concentration intentionally higher. Accuracy of results by MIP OES was evaluated by using standard reference materials (SRM) NIST 1572 and NIST 1575a. In addition, results showed no statistical difference by comparison with those by ICP OES. MIP OES proved to be a suitable technique for the determination of metals in dietary supplements, being a feasible alternative for the quality control of these products.

Optimization of processing parameters and microstructure evolution of (TiB+La2O3)/Ti6Al4V manufactured by laser melting deposition

Due to the intrinsically ultrahigh cooling rate and thermal gradient during laser melting deposition (LMD), columnar-to-equiaxed transition (CET) of grains has been a significant challenge in titanium-based alloys. In this study, two strategies, including the optimization of processing parameters and the addition of ceramics particles, were utilized to promote the CET of Ti6Al4V. The optimal processing parameters of Ti6Al4V were confirmed by response surface methodology (RSM). The width of prior β grains effectively decreases under the minimum dilution of single track. Besides, different contents of TiB2 and La2O3 were added to Ti6Al4V powder and the in situ (TiB + La2O3)/Ti6Al4V composites were manufactured using the identified optimal processing parameters. In situ TiB whiskers segregating at the grain boundaries tailor the coarse columnar to equiaxed grains with La2O3 particles dispersed in the composites. With increasing formation of the reinforcements, equiaxed grain size decreases from 23.3 to 11.9 μm. The ultimate tensile strength of the components was improved by 19.6% and 26.4% compared to that of Ti6Al4V. This work provides systematic solutions to suppress the coarse columnar grains and refine the microstructure for titanium-based alloys.

Preventing swarm detection in extracellular vesicle flow cytometry: a clinically applicable procedure

BackgroundFlow cytometry is commonly used to detect cell-derived extracellular vesicles in body fluids such as blood plasma. However, continuous and simultaneous illumination of multiple particles at or below the detection limit may result in the detection of a single event. This phenomenon is called swarm detection and leads to incorrect particle concentration measurements. To prevent swarm detection, sample dilution is recommended. Since the concentration of particles differs between plasma samples, finding the optimal sample dilution requires dilution series of all samples, which is unfeasible in clinical routine. ObjectivesHere we developed a practical procedure to find the optimal sample dilution of plasma for extracellular vesicle flow cytometry measurements in clinical research studies. MethodsDilution series of 5 plasma samples were measured with flow cytometry (Apogee A60-Micro), triggered on side scatter. The total particle concentration between these plasma samples ranged from 2.5 × 109 to 2.1 × 1011 mL−1. ResultsSwarm detection was absent in plasma samples when diluted ≥1.1 × 103-fold or at particle count rates <3.0 × 103 events·s-1. Application of either one of these criteria, however, resulted in insignificant particle counts in most samples. The best approach to prevent swarm detection while maintaining significant particle counts was by combining minimal dilution with maximum count rate. ConclusionTo prevent swarm detection in a series of clinical samples, the measurement count rate of a single diluted plasma sample can be used to determine the optimal dilution factor. For our samples, flow cytometer, and settings, the optimal dilution factor is ≥1.1 × 102-fold, while the count rate is <1.1 × 104 events·s−1.

A study on geometrical aspects in laser cladding by lateral powder injection technique

Laser cladding is carried out using lateral powder feeding method and the effect of direction of deposition on the clad track geometry is studied. Further, the effect of laser process parameters i.e., laser power and scan speed on the forming characteristics of clad track are also studied. The lateral nozzle with 1 mm diameter feed powder (Inconel 718) with 60° angle to the substrate (Stain Steel-AISI 304). With the different direction of scanning with different laser process parameter, mass flow and carrier gas (Argon) pressure the scanning direction opposite to power flow (+Y) formed uniform clad bed with height, width, and minimum dilution. At higher rate of carrier gas flow the molten poll is well-shielded and preventing oxidation. In addition, 2D thin wall formed, also hardness (360 Hv0.05) of the wall uniform throughout and no porosity throughout the wall.

In Vitro Evaluation of Commercial Probiotic Products Containing Streptococcus salivarius K12 by Assessment of Probiotic Viability and Inhibitory Potency against Respiratory Pathogens

Upper respiratory infections (URI) are the most frequent illnesses, especially in children. The majority of those infections are prescribed broad-spectrum antibiotics, which are associated with various side effects and with the increase in multi-drug-resistant strains. A promising alternative approach is the administration of the probiotic strain Streptococcus salivarius K12 (SSK12) that colonizes the upper respiratory tract (URT) and produces the salivaricins A2 and B, which strongly antagonize the growth of key respiratory pathogens. However, since for food supplements no quality controls of the active probiotic ingredient are mandatory, the efficacy of commercial products containing SSK12 may vary. This study aimed to investigate the in vitro efficacy of several commercial SSK12-containing probiotics, positioned for the prevention of respiratory infections. The parameters evaluated to determine the in vitro efficacy included the viability of the probiotic bacterial strain and the minimum inhibitory dilution (MID) of the probiotic, determined by the agar spot method, against the pathogenic/potential pathogenic bacterial strains Streptococcus pyogenes FF22 and Micrococcus luteus T18. All tests were carried out both 12 and 24 months after manufacturing (AM) for each commercial product. The viability ranged from 9 × 108 to 4.4 × 109 CFU/serving at 12 months AM and from 8.5 × 107 to 2.8 × 109 CFU/serving at 24 months AM. The MID was, in general, positively correlated with the probiotic bacterium viability and varied between the commercial products, ranging from 10−5 to 10−7 at 12 months AM and from 10−4 to 10−7 at 24 months AM. Moreover, the inhibition zones related to the two indicator strains were variable in diameter for different products. The high variation of the in vitro efficacy of commercial products containing SSK12 may explain the different results reported in the literature regarding the clinical benefits of these preparations, and the determination of this parameter may be useful to evaluate the quality of probiotic products containing this bacterial strain.

A passive membrane system for on-line mass spectrometry reagent addition.

Post-separation addition of chemical modifiers in liquid chromatography-mass spectrometry is widely used for improving ionization sensitivity and selectivity. This is typically accomplished using a post-column T-junction, which can result in sample dilution and imperfect mixing. We present a passive semi-permeable hollow fiber membrane approach for the addition of chemical modifiers that avoids these issues. Model compounds were directly infused by flow injection to an electrospray ionization triple quadrupole mass spectrometer after passing through a polydimethylsiloxane hollow fiber membrane. Ionization enhancement reagents were introduced into the flowing stream by membrane permeation from aqueous solutions. Ionization enhancement from volatile acids and bases in positive and negative electrospray ionization was evaluated to assess the feasibility of this approach. The membrane-based apparatus resulted in relative ionization enhancement factors of up to 14×, depending upon the analyte, reagent, and ionization mode used. Ionization enhancement signal stability is reasonable (relative standard deviation of 5-7%) for extended periods from the same reagent solution, and minimal analyte dilution is observed. A proof-of-concept demonstration of the chromatographic "trifluoroacetic acid fix" strategy is presented. An on-line mass spectrometry ionization reagent addition method with potential post-chromatography reagent addition applications was developed using a hollow fiber polydimethylsiloxane membrane. This approach offers a promising alternative to traditional methods requiring additional hardware such as pumps and T-junctions that can result in sample dilution and imperfect reagent mixing.

Humidification Towards Flashback Prevention in a Classical Micro Gas Turbine: Thermodynamic Performance Assessment

Combustion air humidification has proven to be effective to stabilize hydrogen combustion and to avoid flashback apparition in a typical micro Gas Turbine (mGT). However, both the fuel alteration and combustion air dilution will impact the cycle performance. A complete characterization of this thermodynamic impact is essential to ensure that the mGTs become cleaner, and fully flexible to fit with the expectation of future small-scale decentralized power production. Therefore, the objective of this work is twofold: the determination of the necessary dilution for combustion stabilization, depending on the type of fuel, as well as the impact assessment on the cycle performance. In this framework, a hybrid model of the Turbec T100 mGT combustor, combining a 0D Chemical Reactor Network and 1D Laminar flame calculations, is used to first assess the flashback limits. The laminar flame speed is evaluated to predetermine the necessary minimal water dilution of the combustion air to avoid flashback for several CH4/H2blends. Second, a thermodynamic analysis is performed to assess the impact of the flame stabilization measures on the cycle performance of the mGT using Aspen Plus. The 0D/1D simulation results show that the combustor of the Turbec T100 can operate with fuels containing up to 100% hydrogen. However, the thermodynamic analysis shows that the water dilution leads to a decreased electrical performance. Future work consists in the iterative coupling of both 0D/1D and the Aspen model to correctly predict the flashback limits, considering the altering operating conditions. To conclude, with this work, we provide a framework for future mGT operations with alternative fuels.

Influence of bovine and human serum albumin on the binding kinetics of biomolecular interactions.

Bovine serum albumin (BSA) containing buffers are the standard blocking buffer in biosensing, yet human serum is the intended application for most clinical sensors. However, the effect of human serum albumin (HSA) on binding assays remains underexplored. A simple and well-studied assay (human IgG/goat anti-human IgG) was investigated with a surface plasmon resonance (SPR) sensor to address this fundamental question in sensing. Calibrations were performed with buffers containing various concentrations of bovine or human serum albumin, as well as full and diluted bovine or IgG-depleted human serum. It was found that HSA or human serum, but not BSA or bovine serum, significantly affected the SPR shift and binding constants of the assay. Interestingly, large differences were also observed depending on whether the animal or human antibody was immobilized on the SPR chip for detection, highlighting that matrix protein/analyte/receptor interactions play a significant role in the response. We find that the interaction of soluble HSA with human IgG interferes with the recognition region, affecting the binding constant, and thus results obtained in BSA are not necessarily applicable to clinical samples or in vivo conditions. We also clearly demonstrate why a minimum dilution of 1 : 10 is often required in SPR assays to remove most background effects. Taken together, these results show that: (1) BSA does not affect the binding constant between antibodies and thus serves its purpose well when only surface blocking is intended, (2) HSA is an adequate surrogate for human serum in assay optimization, and (3) blocking buffers should be prepared with HSA in the optimization steps of assays to be translated to human blood or serum.

Underground mining technologies at the Kekura deposit

Research subject and objective is to work out exploration data details to optimize the processes of filling the stoped-out areas when choosing a underground mining technologies for a gold ore deposit. Methods of research include an analytical survey of information about the deposit to improve the quality of mining by minimizing dilution and loss of valuable ores when backfilling with hardening mixtures. Research results. The paper provides data about a gold deposit with complex geological, geographical and operational conditions. Design solutions for mining technology with minimum dilution and loss and for the enterprise’s production capacity development are analyzed. The priority of the ore-hosting rock mass state control performance criterion is substantiated. The criterion refers to production costs considering the damage from losses and dilution. Factors of ore dilution in the course of underground mining are generalized and systematized. Some options for mining systems are recommended as launching. The options of mining by open-pit and underground methods are assessed and the time to reach full production capacity is given. It is shown that in the course of development, technologies containing backfilling with hardening mixtures will be a priority. Recommendations are given to provide raw materials for hardening mixtures preparation by recycling own waste and waste from allied industries. Conclusions. The most promising technology for ore mining by underground method provides for backfilling with hardening materials made through demetallization and disposed component properties control

Effect on Various Parameter of Stainless Steel 316L Weld Bead Geometry using Cold Metal Transfer (CMT) Process

This study influences the effect of various process parameters on Cold Metal Transfer (CMT) of stainless steel 316L using mild steel as substrate. CMT has a benefit of a minimal heat input, a high deposition rate, and increased efficiency. Typically, single pass weld beads are utilized for repair and remanufacturing. The geometry of the beads determines the cladding performance of additively produced components. Therefore, optimal range of bead characteristics is necessary to ensure superior mechanical qualities. The parameters includes as: welding current, travel speed and feed speed, were tuned to produce joints with complete penetration depth and zero defects. The weld bead with lower wire travel speed of (2.9 m/min) and higher wire feed speed of (4.9 m/min) at current value of (141A) shows the optimum value of (bead width: 3.56 mm, bead height: 1.72mm, weld penetration: 3.83mm and dilution: 1.5%). This was attributed to the decreases of wire travel speed and increases of wire feed speed ensuring better penetration and larger molten metal. While a higher current value causes the convexity area of the bead to rise, it displays a stronger penetration and minimal dilution.

Kendali Optimal Model Pertumbuhan Mikroalga dalam Chemostat

Microalgae is one of Indonesia's natural potentials that can be utilized in various needs such as producing energy products (bioethanol, biodiesel), biopolymer producing plastic and as a soil mixture for construction engineering, even as waste treatment by absorbing the remaining organic compounds and nutrients or absorb some of the hazardous compounds contained in the waste. One of the microalgae culture media is chemostat. Chemostat is a type of continuous bioreactor that functions for the cultivation of microalgae and other microorganisms that are usually used in laboratory and industrial scales. In this study, control efforts on the microalgae growth model in the chemostat were carried out. This is so that the growth of microalgae reaches the equilibrium value in the minimum possible time. By applying Pontryagin's Minimum Principle and dilution parameters as control variables, it is obtained that the type of control carried out is bang-bang control. Then the control problem is solved numerically using the ICLOCS2 toolbox. The simulation results showed that microalgae were able to reach equilibrium conditions faster by 40.9% under the control. So, it can be said that the system can be controlled optimally.

Where do nursing students make mistakes when calculating drug doses? A retrospective study

BackgroundResearch internationally shows that nursing students find dosage calculation difficult. Identifying the specific aspects of dose calculation procedures that are most commonly associated with errors would enable teaching to be targeted where it is most needed, thus improving students’ calculation skills. The aim of this study was to analyze where specifically nursing students make mistakes when calculating drug doses.MethodRetrospective analysis of written examination papers including dosage calculation exercises from years 1, 2, and 3 of a nursing degree program. Exercises were analyzed for errors in relation to 23 agreed categories reflecting different kinds of calculation or steps in the calculation process. We conducted a descriptive and bivariate analysis of results, examining the relationship between the presence of errors and the proportion of correct and incorrect final answers.ResultsA total of 285 exam papers including 1034 calculation exercises were reviewed. After excluding those that had been left blank, a total of 863 exercises were analyzed in detail. A correct answer was given in 455 exercises (52.7%), although this varied enormously depending on the type of exercise: 89.2% of basic dose calculations were correct, compared with just 2.9% of those involving consideration of maximum concentration. The most common errors were related to unit conversion, more complex concepts such as maximum concentration and minimum dilution, or failure to contextualize the answer to the clinical case. Other frequent errors involved not extracting the key information from the question, not including the units when giving their answer, and not understanding the question. In general, fewer errors in basic dose calculations were made by students at later stages of the degree program.ConclusionsStudents struggle with more complex dose calculations. The main errors detected were related to understanding the task and the key concepts involved, as well as not following the correct steps when solving the problem.

Structure-property correlation of a CoCrFeNi medium-entropy alloy manufactured using extreme high-speed laser material deposition (EHLA)

A near-dense and crack-free CoCrFeNi medium entropy alloy (MEA) coating was fabricated using extreme-high-speed laser material deposition (EHLA). The ultra-low local heat input associated with the EHLA process benefitted in attaining minimal dilution and heat-affected zone. The MEA coating retained the single-phase face-centered cubic (FCC) phase structure associated with the original powder feedstock without any evidence of elemental segregation. The coating exhibited a “bonfire”-like clustered fine grain structure near the substrate interface with the large columnar grains in the subsequent layers further from the substrate. Anisotropic mechanical deformation behaviour was observed at a localized level, but homogenous mechanical properties were evidenced by microstructure-mechanical property correlations at the bulk level. The EHLA process offers exciting possibilities for the development of next-generation dense and crack-free coatings for extreme engineering applications.

Application of the method of atomic emission spectroscopy with microwave (magnetic) plasma in the processes of identifying the chemical composition of steelmaking waste

As part of the work done, an assessment was made of the possibility of using the method of atomic emission spectral analysis with microwave (magnetic) plasma in the processes of identifying the chemical composition of waste from the metallurgical industry. The features of the design of the domestic device for atomic emission analysis are described, the main advantages are noted, which include the ability to work with concentrated samples with a complex salt background, as well as the possibility of using gases (argon/nitrogen) of technical purity. The main analytical lines for a number of metals have been selected, an internal standard based on water-soluble yttrium compounds has been selected, which makes it possible to level fluctuations in the salt background of the analyzed samples. The adequacy of the data obtained for acidic metal-containing solutions with a minimum (10 times) dilution was assessed. It has been established that a decrease in the dilution factor can significantly reduce the probability of error and improve the quality and speed of analytical control of various materials (including mineral raw materials). As part of the tests, the composition of metalchips selected at various production sites of a machine-building enterprise in the Moscow Region, as well as the composition of the metallurgical scale of the forging and heat treatment of metal, were determined and identified. It has been proven that the initial concentration of salts in the analyzed samples does not significantly affect the reliability of the results obtained, and the error of the analysis results does not exceed 2&ndash;3%. The data obtained on the possibility of using atomic emission spectrometers with microwave (magnetic) plasma of domestic production will make it possible to take a step towards import substitution, which in a difficult geopolitical situation will make it possible to take a step towards the implementation of the concept of import substitution. The authors express their gratitude to N. E. Kruchinina, Doctor of Engineering Sciences, professor, head of the chair for Industrial Ecology, MUCTR, and V. A. Kuchumov, Candidate of Chemical Sciences, head of the laboratory of JSC Spetsmagnit, for help in the development of individual components of the device (plasmatron design) and assistance in research.

Laser metal deposition characterization study of metal additive manufacturing repair of rail steel specimens

ABSTRACT Research on rail steel repair with Stellite 6 powder using a laser metal deposition process was investigated and reported in this study. Rail failures due to excessive wear and other rail head defects can increase the risk of operation and reliability problems in service life. This study examines the deposited material compatibility of a cobalt-based alloy, Stellite 6 with the head-hardened R350HT grade rail steel substrate. Materials characterization work includes metallurgical, wear, and shear properties testing and analysis. Microstructural analysis and hardness measurements of the cross-section from raster scan pattern deposition strategy of Stellite 6 on rail steel substrate surface showed minimal dilution and high hardness of the deposited layer with no presence of defects. Experimental testing of rail wear was conducted using a laboratory ball-on-disc tribometer setup and the wear coefficients for Stellite 6 and rail steel were derived from the wear volume analysis using Archard’s wear model. The material interface bond strength was evaluated from shear testing and analysis to measure the shear interface strength of the metallurgical bond between deposited material on a rail steel substrate.

Surface finish, microhardness and microstructure of laser metal deposited 17-4PH stainless steel

Laser metal deposition is a metal-based additive manufacturing technology. It is a very sensitive and complex process because of the different process parameters involved and the interrelations between these parameters. A thorough understanding of the underlying physics of the process is essential in developing a comprehensive database of the properties of materials processed with this technology. The main objective of this study was to investigate the effect of laser power on a laser-deposited 17-4 precipitation hardenable stainless steel alloy. The as-built microstructure, phase composition, microhardness and surface finish were analysed. The results show that a defect-free sample with good metallurgical bonding and minimal dilution can be produced using high laser power in the range 1400–2600 W and a scanning speed of 0.6 m/s. The microstructure in the clad layer was dominated by martensite and an improvement in surface finish and maximum hardness was observed with increased laser power. Significance: To fully benefit from the additive manufacturing technology, a comprehensive database of the material properties of alloys produced with this technology is required. This study expands on the body of knowledge related to the additive manufacturing of a 17-4PH stainless steel alloy, particularly highlighting the possibility of producing fully dense parts using higher laser power and scanning speed. These two parameters could significantly reduce the build time.