Investigation of laser deposited wear resistant coatings on railway axle steels

Railway axles are one of the most critical components in rail industry since their failure can lead to the derailment of railway vehicles and loss of lives and properties. These components suffer from a wide range of damage including corrosion, electrical arcing, and fatigue and most importantly wear due to excessive loading. Every year rail operators around the world scrap thousands of railway axles due to the size of their two bearing journals being under tolerances and sizes defined for them. The current standards for manufacturing and maintenance of rail axles only allow for non-thermal processes such as brush plating to be used to repair the worn rail axles as thermal processes as they may create heat affected zones with degraded properties in these components. In this study the possibility of using laser cladding which is a thermal process as a repair technology for refurbishment of railway axles is investigated which was proposed for the first time in 2010 by Hardchrome Engineering Pty Ltd, Melbourne, Australia. The economic rationale behind this idea was that replacing each worn axle would cost 2500 Australian dollars whereas repairing them with laser cladding would cost only 1000 Australian dollars per axle, provided that the feasibility of this technology and suitability for railway axle applications is proven. Mild steel which is one of the most widely used materials in the manufacturing of rail axles was used to prepare hour glass fatigue samples to be tested under rotary bending fatigue condition using a dedicated testing machine which was designed and used at Hardchrome Engineering. These samples were tested without any laser deposition to demonstrate the fatigue data of axles which were not worn. To simulate worn railway axles, a groove was machined in each fatigue sample which was later filled by laser cladding as a simulation of a refurbished rail axle. Two different cladding materials were used to build up undersize machined samples which were 420 stainless steel and CrMoV. The laser clad samples were then heat treated at a wide range of temperatures to investigate the effect of post-clad heat treatment conditions on the fatigue properties of laser clad samples. The fatigue results of the clad samples were compared to those of the non-clad samples to investigate the effect of laser cladding on the fatigue properties of the samples

Effects of training in the Morris water maze on the spatial learning acquisition and VAChT expression in male rats

"n  "n  Background and the purpose of the study: It has been well established that cholinergic pathway plays an important role in learning and memory processes. The present study was designed to evaluate the effects of Morris water maze (MWM) training on spatial memory acquisition and expression of the vesicular acetylcholine transporter (VAChT) in male rats. "n  Methods: In this study, training trials of all groups of animals were conducted in the MWM task. Rats received one training session consisting of four trials per day which continued for another four consecutive days. Controls received visible platform MWM training. The escape latency, the traveled distance and swimming speed for each rat were recorded and used to evaluate the performance of the animal during training period. For evaluation of expression of VAChT protein levels, brain tissues from animals in each experiment were obtained immediately after the last trial on the related experimental day and processed for immunohistochemistry staining and western blotting analysis. "n  Results: There was a significant difference between animals subjected to one day training and those receiving four days of training in escape latency and travel distance. There were an apparent increase in VAChT immunoreactivity in the medial septal area (MSA) and CA1 region of the hippocampus in one day and four day trained animals compared with controls (visible group). Quantitative immunostaining analysis by optical density measurements in the CA1 region and evaluation of immunopositive neurons in medial septal area of brain sections confirmed qualitative findings. Assessment of VAChT protein level expression in hippocampus by western blotting evaluation showed the same pattern of immunohistochemistry results. "n  Conclusion: Overall, results of this study reveal changes in cholinergic neuron activity in different stages of training in the MWM task. Data suggest that there is a significant level of cholinergic neuronal activity during early stages of the training especially in the hippocampus region that may contribute to the apparent increase in VAChT expression

Thermal expansion of functionally graded and wafer-layered structures produced by laser direct metal deposition

A range of engineering alloys was selected to create two distinct sets of structures. One was functionally graded materials (FGM) - using pairs of these alloys - and the second type was a series of wafer-layered structures using pairs of these alloys in different combinations. The aim of this investigation was to identify unique sets of structures of alloys which provide very different coefficients of thermal expansion (CTE) compared to those of individual elements. The process used to create these structures was laser direct metal deposition (DMD) additive manufacturing technology. The linear thermal expansion coefficients of these samples were measured and the results show that specific sets of FGM and wafer type structures of specific constituent metal alloys can be fabricated by DMD, in which the overall coefficient of thermal expansion of these new structures is significantly different from that of each alloy when measured individually. FGM and wafer type structures of specific constituent metal alloys have lower CTE than those of original alloys

A study of laser cladding with 420 SS powder on the integrity of the substrate meta

Laser cladding is a thermal process for depositing a metallic alloy on to a parent metal to repair corrosion, erosion, wear or other physical damage. The present work studies the effects of the laser cladding process on the integrity of metal substrates and the bond between the cladding layer and the base metal. It also evaluates some physical characteristics of the cladding layer, in this case grade 420 stainless steel. The research compares the work with Tungsten Inert Gas (TIG) welding and concludes that, due to the small size of the heat-affected zone, this laser cladding process does not adversely affect the physical properties of the metallic substrates

Tensile strength of functionally graded and wafer layered structures produced by direct metal deposition

Purpose - This paper aims to investigate the changes in tensile properties of novel functionally graded materials (FGMs) and wafer structures created by direct metal deposition (DMD) additive manufacturing (AM) technology. Design/methodology/approach - Laser-assisted DMD was used to create two innovative sets of metallic structures - the functionally graded and wafer-layered structures - using pairs of six different engineering alloys in different combinations. These alloys were selected due to their high popularity within a diverse range of industries and engineering applications. The laser-assisted DMD was selected as a suitable technique to create these complex structures because of its capability to deposit more than one alloy powder at a time. After creation of these structures, their tensile strength was tested in a series of tensile tests and the results were compared with those of single alloy samples. Findings - It was observed that the mechanical properties of FGMs and wafer structure samples were clearly different from those of the single alloy samples, a fact which creates a whole pool of opportunities for development of new materials or structures with desired mechanical properties that cannot be achieved in single alloy parts. Originality/value - The study demonstrates the application of the DMD process to produce unique structures and materials, which would be high in demand in engineering applications, where metallic parts are exposed to high loads and where excessive tensile stresses may adversely affect the performance of such parts

Protective effects of some medicinal plants from Lamiaceae family against beta-amyloid induced toxicity in PC12 cell

Background: Excessive accumulation of beta-amyliod peptide (Aβ), the major component of senile plaques in Alzheimer's disease (AD), causes neuronal cell death through induction of oxidative stress. Therefore, antioxidants may be of use in the treatment of AD. The medicinal plants from the Lamiaceae family have been widely used in Iranian traditional medicine. These plants contain compounds with antioxidant activity and some species in this family have been reported to have neuroprotective properties. In the present study, methanolic extract of seven plants from salvia and satureja species were evaluated for their protective effects against beta-amyloid induced neurotoxicity.Methods: Aerial parts of the plants were extracted with ethyl acetate and methanol, respectively, by percolation at room temperature and subsequently, methanolic extracts of the plants were prepared. PC12 cells were incubated with different concentrations of the extracts in culture medium 1h prior to incubation with Aβ. Cell toxicity was assessed 24h after addition of Aβ by MTT assay.Results: Satureja bachtiarica, Salvia officinalis and Salvia macrosiphon methanolic extracts exhibited high protective effects against Aβ induced toxicity (P<0.001). Protective effects of Satureja bachtiarica and Salvia officinalis were dose-dependent.Conclusion: The main constituents of these extracts are polyphenolic and flavonoid compounds such as rosmarinic acid, naringenin, apigenin and luteolin which have antioxidant properties and may have a role in neuroprotection. Based on neuroprotective effect of these plants against Aβ induced toxicity, we recommend greater attention to their use in the treatment of Alzheimer disease

Screening seven Iranian medicinal plants for protective effects against β-Amyloid-induced cytotoxicity in cultured cerebellar granule neurons

Background and objectives: Alzheimer's disease (AD) as a neurodegenerative disorder is the most common form of dementia in the elderly. According to the amyloid hypothesis, accumulation of amyloid beta (Aβ) plaques, which are mostly constituted of Aβ peptide aggregates, triggers pathological cascades that lead to neuronal cell death. Thus, modulation of Aβ toxicity is the hopeful therapeutic approach for controlling the disease progression. Recently, several studies have indicated promising findings from herbal extracts against Aβ cytotoxicity. The aim of the present study was to assess the protective effect of the methanol extract of seven medicinal plants from Iran on Aβ-induced toxicity in primary neuron culture. Method: The methanol extracts of plants were prepared by maceration method. Primary cerebellar granule neurons (CGNs) were taken from male mice at postnatal days 6-7 and cultured in cell culture medium containing 10% FBS and 25 mM KCl. After seven days in vitro (DIV7), the cells were incubated with aggregated Aβ (10 μM) alone or in combination with different concentrations of extracts in the cultured medium for 24 h and cell viability was assessed by MTT assay. Results: Our results indicated that Sanguisorba minor, Cerasus microcarpa, Ferulago angulata, Amygdalus scoparia and Rosa canina extracts significantly ameliorated Aβ-induced toxicity which indicated the protective effect of these extracts. Protective effects were not observed for Stachys pilifera and Alhagi pseudalhagi extracts. Conclusion: Based on the protective effects of these plants against Aβ-induced toxicity, we recommend greater attention to their use in the treatment of Alzheimer's disease