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The present work aims at developing the laser cladding technology by means of an active fiber laser source applicable for hardfacing of martensitic steel turbine blades. It also aims to investigate two process parameter conditions to reproduce two different heat inputs, in order to highlight the effect of the thermal input on the thermal alteration and dilution of the substrate material and clad layer.

The experimentation was performed initially at a sample level, reproducing the material and thickness of the blade leading edge, then on an industrial real component. Cladding process parameters were experimentally selected and two different process parameter conditions, at different specific energy, were determined. The microstructural and geometrical features of the clad samples were analyzed both by optical microscopy and scanning electron microscopy, in this latter case combining the information supplied by different probes, among which the EDX microanalysis to obtain chemical profiles. Hardness distribution was also evaluated by means of Vickers hardness tester.

All the two investigated conditions were suitable for laser cladding of the blade leading edge, since a crack and pore free clad layer with a strong metallurgical bond to the substrate was obtained. The experimented two different heat inputs affected the extension of the HAZ as well the chemical and geometrical dilution. The clad integrity was preserved in both cases. The condition at higher specific energy was chosen to clad the turbine blade. The high specific energy condition was preferred because the iron dilution in the clad layer was inferior.

Further research is needed to correlate the chemical dilution and the thermal alteration introduced by the laser cladding process on such a kind of substrate at different process parameter conditions to the wear and corrosion resistance of the turbine blade.

Laser cladding process with an innovative active fiber laser source of the leading edge of a steam turbine blade was developed. Progress achieved in laser cladding technology development is of practical value for manufacture of turbine blades, made of martensitic steels.

The paper investigates the effect of different energy input on the laser cladding of steam turbine blades, mainly used in coal, gas and nuclear plants to produce electricity by heating water to create steam. The laser cladding process is an effective technology to increase the steam blades toughness and resistance to creep, stress and corrosion. This increase in the turbine blade properties contributes to extend the life of such a critical components, decreasing cost and time of substitution and ensuring better service conditions.

The most original aspect of the paper is related to the focus on the difference between the chemical and the geometrical dilution, being the first one mainly related to the corrosion and wear resistance of the clad layer, while the later mainly regards the clad layer adhesion to the substrate. More in general the paper presents one of the first experiments accomplished while making use of the active fiber laser source.

This paper aims to compare the wear performance of carbon steel specimens clad with TiC, WC and TiN powders by the gas tungsten arc welding (GTAW) method under optimum processing conditions.

Various ceramic powders (TiC, WC and TiN) with equal percentages by weight were prepared for use as cladding materials to compare their effects on wear resistance. The wear behaviors of different cladding specimens were evaluated with a rotating-type tribometer under dry sliding conditions. The cladding microstructures were characterized by optical microscopy, scanning electron microscopy and X-ray energy dispersive spectrometry.

The experimental results confirmed that the hardness was also much higher in the carbon steel with cladding than in carbon steel without cladding. The pin-on-disc wear test showed that the wear-resistance of ceramics clad with TiC is better than that in ceramics clad with WC or TiN. The wear scar area of the specimen with TiC cladding was only one-tenth that of carbon steel without cladding.

The experiments confirm that the cladding surfaces of ceramic particles reduce wear rate and friction.

This paper aims to investigate the effect of four important process parameters (i.e. laser focal distance, travel speed, feeding gas flow rate and standoff distance) on the size of single clad geometry created by coaxial nozzle-based powder deposition by high power laser.

Design of experiments (DOE) and statistical analysis methods were both used to find optimum parameter combinations to get minimum sized clad, i.e. clad width and clad height. Factorial experiment arrays were used to design parameter combinations for creating experimental runs. Taguchi optimization methodology was used to find out optimum parameter levels to get minimum sized clad geometry. Response surface method was used to investigate the nonlinearity among parameters and variance analysis was used to assess the effectiveness level of each problem parameters.

The overall results show that wisely selected four problem parameters have the most prominent effects on the final clad geometry. Generally, minimum clad size was achieved at higher levels of gas flow rate, travel speed and standoff distance and at minimum spot size level of the laser focal distance.

This study presents considerable contributions in assessing the importance level of problems parameters on the optimum single clad geometry created laser-assisted direct metal part fabrication method. This procedure is somewhat complicated in understanding the effects of the selected problem parameters on the outcome. Therefore, DOE methodologies are utilized so that this operation can be better modeled/understood and automated for real life applications. The study also gives future direction for research based on the presented results.

Stainless-clad bimetallic steels (SCBS) are widely investigated in some extremely environmental applications areas, such as polar sailing area and tropical oil and gas platforms areas, because of their excellent anticorrosion performance and relatively lower production costs. However, the properties of SCBS, including the mechanical strength, weldability and the anticorrosion behavior, have a direct relation with the manufacturing process and can affect their practical applications. This paper aims to review the application and the properties requirements of SCBS in marine environments to promote the application of this new material in more fields.

In this paper, the manufacturing process, welding and corrosion-resistant properties of SCBS were introduced systematically by reviewing the related literatures, and some results of the authors’ research group were also introduced briefly.

Different preparation methods, such as rolling composite, casting rolling composite, explosive composite, laser cladding and plasma arc cladding, as well as the process parameters, including the vacuum degree, rolling temperature, rolling reduction ratio, volume ratios of liquid to solid, explosive ratio and the heat treatment, influenced a lot on the properties of the SCBS through changing the interface microstructures. Otherwise, the variations in rolling temperature, pass, reduction and the grain size of clad steel also brought the dissimilarities of the mechanical properties, microhardness, bonding strength and toughness. Another two new processes, clad teeming method and interlayer explosive welding, deserve more attention because of their excellent microstructure control ability. The superior corrosion resistance of SCBS can alleviate the corrosion problem in the marine environment and prolong the service life of the equipment, but the phenomenon of galvanic corrosion should be noted as much as possible. The high dilution rate, welding process specifications and heat treatment can weaken the intergranular corrosion resistance in the weld area.

This paper summarizes the application of SCBS in marine environments and provides an overview and reference for the research of stainless-clad bimetallic steel.

The purpose of this paper is to demonstrate the preliminary work on using laser cladding technology for the restoration of structural integrity.

The primary methodology used in this research is to develop a laser cladding‐based metal deposition technique to articulate restoration of structural geometry affected by corrosion damages. Following from this method, it is planned to undertake further work to use the laser cladding process to restore geometry and the associated static/fatigue strength.

This work has found that it is possible to use laser cladding as a repair technology to improve structural integrity in aluminium alloy aircraft structures in terms of corrosion reduction and geometrical restoration. Initial results have indicated a reduction of static and fatigue resistance with respect to substrate. But more recent works (yet to be published) have revealed improved fatigue strength as measured in comparison to the substrate structural properties.

The research is based on an acceptable materials processing technique.

The purpose of this paper is to test the wear behavior of a carbon steel surface after cladding by gas tungsten arc welding (GTAW) method to enhance wear resistance.

The microstructures, chemical compositions, and wear characteristics of cladded surfaces were analyzed by scanning electron microscopy (SEM), and energy dispersive X‐ray spectroscopy (EDX). A rotating‐type tribometer was used to evaluate the wear characteristics of cladded specimens under dry sliding conditions at room temperature. The dry sliding wear resistance of the coatings was tested as a function of applied load and sliding time, and wear mechanisms were elucidated by analyzing wear surfaces.

The experimental results revealed an excellent metallurgical bond between the composite coating and substrate. The coating was uniform, continuous, and almost defect‐free, and particles were evenly distributed throughout the cladding layer. Hardness was increased from 200 HV in the substrate to 650‐800 HV in the modified layer due to the presence of the hard TiC phase. The excellent wear resistance and very low load sensitivity observed in the dry sliding wear test of the intermetallic matrix composite coating were due to the high hardness of TiC and the strong atomic bonds of the intermetallic matrix.

The experiments in this study confirm that, by reducing friction and anti‐wear, the cladding layer prepared using the proposed methods can prolong machinery operating life.

The thermal management of printed circuit boards with high component density is increasingly becoming an important factor in the efficiency and reliability of electronic systems. A well‐proven technique, which has been used to produce multilayer circuit boards in quantity for several years, is to incorporate metal foils. The metal foils significantly improve heat removal and impart to the circuit board a thermal expansion behaviour closely matching that of the ceramic chip carrier. Roll‐clad Copper‐Invar‐copper (CIC) and copper‐molybdenum‐copper (CMC) foils have been used for this purpose. This paper reports on the first use of Mo30Cu foils, a material produced by powder metallurgy consisting of 70% molybdenum and 30% copper. Contraves AG manufacture SMT multilayer circuit boards incorporating Mo30Cu foils produced by Metallwerk Plansee GmbH. With regard to machinability and physical characteristics, Mo30Cu foils are superior to roll‐clad foils. First of all, the high elastic modulus of Mo30Cu foils is worth mentioning. It positively influences thermal stability and mechanical stiffness of the circuit board.

The purpose of this work is to explore predictive model approaches for selecting laser cladding process settings for a desired bead geometry/overlap strategy. Complementing the modelling challenges is the development of a framework and methodologies to minimize data collection while maximizing the goodness of fit for the predictive models. This is essential for developing a foundation for metallic additive manufacturing process planning solutions.

Using the coaxial powder flow laser cladding method, 420 steel cladding powder is deposited on low carbon structural steel plates. A design of experiments (DOE) approach is taken using the response surface methodology (RSM) to establish the experimental configuration. The five process parameters such as laser power, travel speed, etc. are varied to explore their impact on the bead geometry. A total of three replicate experiments are performed and the collected data are assessed using a variety of methods to determine the process trends and the best modelling approaches.

There exist unpredictable, non-linear relationships between the process parameters and the bead geometry. The best fit for a predictive model is achieved with the artificial neural network (ANN) approach. Using the RSM, the experimental set is reduced by an order of magnitude; however, a model with R2 = 0.96 is generated with ANN. The predictive model goodness of fit for a single bead is similar to that for the overlapping bead geometry using ANN.

Developing a bead shape to process parameters model is challenging due to the non-linear coupling between the process parameters and the bead geometry and the number of parameters to be considered. The experimental design and modelling approaches presented in this work illustrate how designed experiments can minimize the data collection and produce a robust predictive model. The output of this work will provide a solid foundation for process planning operations.

To investigate the influences of environmental stresses on board‐embedded polymeric waveguides.

Optical multimode waveguides were embedded on printed circuit boards using commercial polymers. The optical‐PCBs varying in board structure and in optical build‐up materials were exposed to heat, moisture and ionic‐contaminants in accelerated reliability tests. The influence of stress factors on the structural integrity and functional parameters, namely the refractive index and optical transmissivity, was investigated at the key communication wavelengths.

Isothermal annealing reduced the refractive index to the greatest extent. The optical‐PCB structure with an optical surface build‐up layer was observed to be more vulnerable under temperature shock when compared with the optical‐PCB with optical inner layer. The buffer layer beneath the optical build‐up was found to improve the stability of the optical waveguides significantly. The results indicated of wavelength dependence to the aging factor with a failure mechanism. The factors affecting the performance and reliability of polymer‐based optical waveguides on PCBs were discussed.

More experimental data and investigations of failure mechanisms are required to ultimately obtain sufficient reliability statistics for accurate life‐time prediction models.

Optical interconnects are seen as a promising solution to overcome performance limitations encountered with high‐frequency electrical interconnections. As an emerging technology, only a limited amount of reliability data on optical/electrical packages is available. The paper investigates the influences of environmental stresses on board‐embedded polymeric waveguides.

Stainless steel strip cladding is a flexible and economical way of depositing a corrosion resistant, protective layer on a load‐bearing mild or low alloy steel. Strip cladding is therefore widely used in the production of components for the chemical, petrochemical and nuclear industries, for example.