Multilayer Cladding Research Articles

Effect of Weibull parameters and crack distribution on the failure probability of multi-layered SiC cladding

In this paper, an improved Weibull failure probability model which considers initial cracks distributed in the cladding has been proposed. Considering the coupling of force, heat and irradiation acting on the multi-layered SiC cladding, failure probabilities of the cladding under different conditions have been obtained. The results indicate that compared to linear heat rate, the cladding is more sensitive to changes in inner pressure of fuel elements. The cladding can be optimized by adjusting the proportion of different layers. Further investigations indicate that effect of different Weibull parameters of CVD SiC on the failure probability is small and can be ignored in real fuel elements. Meanwhile, cracks in SiC composite layer and crack length have little effect on the failure probability. However, the initial inclination angle can affect the failure probability greatly. Results indicate that the most dangerous inclination angle in the cladding is about 73°.

Study on the Hot Cracking Law of Inconel 690/52M Welding Material on F304LN Base Metal by Multi-Layer Cladding

During the welding of 690 nickel-based alloy, solidification cracking (SFC) and ductility-dip cracking (DDC) easily forms, which has a negative effect on the quality of welded joints and service life. The present study examined the effects of welding heat input and cladding layers on the SFC and DDC, as well as their formation mechanism. The microstructure observation, elemental distribution, and Varestraint test were carried out. The results show that SFC and DDC were formed for the Inconel filler metal 52M, and SFC is more prone to form than DDC. The alloy elements such as Fe, Si, C, and P from base metal can expand the solidification temperature range, such that the SFC sensitivity increases. With the increase of welding heat input, the grain size of cladding metal is increased with a great SFC sensitivity. The increasing welding heat input also makes DDC possible due to the formation of a large angle grain boundary.

Effect of multi-layer laser cladding of Stellite 6 and Inconel 718 materials on clad geometry, microstructure evolution and mechanical properties

The multi-layer laser cladding of high temperature resistance alloys i.e., Stellite 6 and Inconel 718 on SS316 was developed with an objective to investigate the effect of cladding materials on clad geometry, microstructure evolution and mechanical properties. The analysis was performed using Optical Microscope, SEM with EDS and Microhardness tester respectively. The results have shown a comparable difference in all the aspects of study. A 50% and 30% increment in clad height is measured while cladding at 12 mm/s and 16 mm/s scan speed as compared to 20 mm/s for both the alloys. The Inconel 718 deposits has shown 15–25% larger clad height, than Stellite 6. Also, under varying process parameters, 15–45% penetration depth and 10–15% higher dilution in Inconel 718 is obtained. SEM results have revealed that the microstructure evolution from top to bottom of the clad is nearly the same except at low laser powers. The decrement in microhardness is observed near the interface due to dilution and is higher in the first layer than the second layer. Whereas, the low dilution obtained in the second layer is because of the newly deposited layer over the substrate. The present work has given the optimum parameters (laser power and scan speed) as 2900 W and 20 mm/s for Stellite 6 and 3400 W, 12 mm/s for Inconel 718 respectively.

Analysis of the Heat Resistance of Multilayer Clothing Packages

Clothing fabrics are rarely used individually as the only layer protecting the body against different outer factors. Especially in cold climates, human attire is usually composed of several layers constituting together a multilayer set of textile materials. The purpose of this work was to analyse the impact of the number of layers on the thermal resistance of multi-layer clothing packages. Two-, three- and four-layer packages were made from woven fabrics of different structure. The packages were tested for thermal resistance by means of a Permetest instrument, made by Sensora (Czech Republic). The tests were carried out for individual materials forming the layers of the packages and for entire packages. Based on the research conducted and analysis of the results, it was found that the number of layers has a significant impact on the thermal resistance of multi-layer clothing packages. The thermal resistance of the multilayer textile packages measured was a little lower than the sum of the thermal resistance of the particular layers creating the packages. On the basis of the results, the thermal contact resistance and boundary effect were also discussed.

Is an Anion Generating Face Mask the Ultimate Solution for Airborne Pollutants?

Airborne negatively charged ions have long been used for cleaning spaces by removing dust particles and stunting bacterial, fungal, and viral growth. Likewise, the ongoing pandemic has made the use of face masks inevitable. A novel concept has been established by integrating the benefits of negatively charged air ions with the advantages of conventional facemasks to tackle the current situation and offer additional advantages as well. The newly devised concept can be used by any individual who can wear a mask but will be especially useful for healthcare workers, infected individuals and those concerned about the possibility of inhaling harmful airborne particles. This new facemask concept may be crucial in reducing the risk of airborne diseases and is a far better choice in adequate protection as opposed to the standard single or multi layered cloth mask. This new mask concept is simple, cost effective, and appears to perform extraordinarily well. It requires no outside power source and is even washable and reusable. It is also remarkably comfortable and can be designed so that one size fits most adults.

Studying the impact of multilayer fabric on the characteristic of temperature distribution under the influence of fire

The paper reports the results of research on different structures for multilayer clothing fabrics characterized by the occurrence of air spaces between individual layers. The main goal of this structure was improving the thermal protective properties of the fabric to be more effective than single-layer fabrics. Three types of fabric were investigated: a single-layer fabric; a self-bonded two-layer fabric, where the outer layers are joined by means of a tie-up in the process of weaving; and a self-bonded three-layer fabric, where the middle layer with fewer warp and weft threads join both outer layers. All the fabrics were produced under the same technical and technological conditions using flame-retardant yarn. Moreover, the value of the final mass per unit area for all the fabrics is similar; for the thermal protective test the single-layer fabric is double-folded. The thermal protective properties of the fabrics characterized by means of temperature distribution on the textile surface were tested using a thermal imaging camera. The three-layer fabric has the most favorable thermal protection in comparison with the double-folded single-layer and self-bonded two-layer fabrics, despite all fabrics having the same mass per unit area.

Mechanism and prediction models for interfacial shear separation of claddings excited by Love waves

The forced propagation solution of interfacial shear stress of multilayer cladding structure excited by Love waves is derived by the integral transformation method, and the shear resonance mechanism of interfacial separation is further revealed. The coupling resonance between the excitation frequency and structure intrinsic property causes the peak of interfacial shear stress amplitude, which results in interfacial shear separation at certain frequency bands. It is found that the coupling resonance frequency of interfacial shear stress is only dependent on the inherent properties of the structure, around which the frequency band of interfacial shear separation is formed. The coupling resonance frequency decreases with the increase of the cladding thickness or shear wave velocity difference between the cladding and substrate. The influence of cladding material parameters on interfacial shear stress is greater than that of matrix material parameters. The experimental results support the theoretical analysis results. The conclusions presented could have potential applications in ultrasonic deicing/defrosting/de-sanding and/or coatings protection.

Impact of seam on liquid transmission behaviour of multi-layered ensembles using sweat and water

Present study is focussed on the effect of seam on the moisture transmission in liquid form. Behaviour of actual sweat is found to be different from pure water used while evaluating the performance of multilayer clothing systems in seamed and unseamed condition in terms of their in-plane (wetting time) & cross-plane moisture transmission and overall moisture management capacity. Uni-directional seam shows higher wetting time at the inner surface as well as better cross-plane transmittance, and hence better overall moisture management capacity as compared to bi-directional stitched and unseamed fabrics. In all the cases, sweat shows less wetting time than water. Multi-layered ensemble with polyester spacer fabric as middle layer exhibits better overall moisture management properties in comparison to layered ensemble with fleece fabric as middle layer both in seamed and unseamed conditions. Seam type plays a most significant role followed by type of layered ensembles then solution type in affecting the overall moisture management behaviour of seamed ensembles.

Microstructure and Wear Resistance of Multi-Layer Ni-Based Alloy Cladding Coating on 316L SS under Different Laser Power.

We prepared three kinds of Ni based alloy cladding coatings on 316L stainless steel at different power levels. The microstructure of the cladding layer was observed and analyzed by XRD, metallographic microscope, and SEM. The hardness of the cladding layer was measured, and the wear resistance of it was tested by a friction instrument. The results show that the effect of laser cladding is good, and it has good metallurgical bonding with the substrate. Different microstructures such as dendritic and equiaxed grains can be observed in the cladding layer. With the increase in laser power, more equiaxed and columnar dendrites can be observed. The phase composition of the cladding layer is mainly composed of γ–Ni solid solution and some intermetallic compounds such as Ni3B, Cr5B3, and Ni17Si3. The results of EDS show that there are some differences in the distribution of C and Si between dendrites. The hardness of the cladding layer is about 600 HV0.2, which is about three times of the substrate (~200 HV0.2). Through the analysis of the wear morphology, the substrate wear is serious, there are serious shedding, mainly adhesive wear, and abrasive wear. However, the wear of the cladding layer is slight, which is abrasive wear, and there are some grooves on the surface.

Literature review to integrate information to assist workers to select masks even at workplaces without occupational health personnel.

BackgroundWith the COVID‐19 pandemic, the idea of universal mask wearing to prevent infecting others when one becomes infected has prevailed among people. In general, any workplace is not exempt and workers are required to wear a mask while working at the sites.ObjectivesThis study aims to integrate information to assist workers to select effective protectors for the prevention of droplet infection even at workplaces without occupational health personnel.MethodsA total of 94 studies were included in this study: 91 studies were identified in MEDLINE, which was used for the literature search, and an additional three studies were identified from other information sources. The studies were checked to eliminate duplication and narrowed down to 31 based on the titles and abstracts. The contents of the 31 studies were read through and then 19 studies were extracted for careful reading.Results and ConclusionsRegarding the protectors used at workplaces, it was suggested that (1) workers continue to use respiratory protectors as needed at sites where respiratory protectors such as an N95 respirator had to be used even before the spread of COVID‐19 and (2) wear surgical masks, multi‐layer cloth masks, or hybrid fabric masks made of several types of fabrics that are recommended in terms of preventing dissemination of droplets and protecting against inhalation of droplets, selected according to the working conditions, taking account of air permeability, breathability, and durability.

U75V钢轨多层多道激光熔覆工艺研究

U75V钢轨多层多道激光熔覆工艺研究

Multi-zone and Multi-layer Laser Cladding Path Planning for Scrapping Mechanical Parts Considering Interlaminar Time Interval

Multi-zone and Multi-layer Laser Cladding Path Planning for Scrapping Mechanical Parts Considering Interlaminar Time Interval

Optimization of Multilayer Clothing Assemblies for Thermal Comfort in Cold Climate

Optimization of Multilayer Clothing Assemblies for Thermal Comfort in Cold Climate

Microstructure and high-temperature wear behaviour of Inconel 625 multi-layer cladding prepared on H13 mould steel by a hybrid additive manufacturing method

To improve the high-temperature performance of a hot-working mould, high-temperature wear-resistant multi-layer laser cladding was prepared on the forming surface of the mould by a hybrid additive manufacturing (HAM) method. First, an Inconel 625 multi-layer cladding was fabricated on the H13 mould steel by laser cladding. Then, the multi-layer laser cladding was milled by CNC. Finally, the milled multi-layer cladding was subjected to ultrasonic surface rolling (USR) treatment. The microstructure and high-temperature wear behaviour of the multi-layer cladding prepared by HAM were studied using SEM, EDS, and a high-temperature tribometer. The results show that the multi-layer laser cladding after USR has a smooth nanolayer. The surface roughness is below 0.15 μm. The multi-layer cladding has better high temperature wear resistance than the substrate. The microstructure of the multi-layer cladding from the surface to the substrate is composed of coaxial, columnar, and dendritic grains. After USR treatment, the dendritic grains are grown in the processing direction and significantly refined.

Microstructure and Mechanical Properties of Nickel-Based Coatings Fabricated through Laser Additive Manufacturing

In this study, single-layer and three-layer nickel-based coatings were fabricated on 316L SS by laser additive manufacturing. The phase characterization, microstructure observation, and microhardness analysis of the coatings were carried out by X-ray diffraction (XRD), scanning electron microscope (SEM), and microhardness tester. And the wear resistance of the coatings was analyzed through dry sliding friction and wear test. The results show that the cross-section microstructure of the three-layer nickel-based coating is different from that of the single-layer one under the influence of heat accumulation; the dendrite structure in the central region of the former is equiaxial dendrite, while that of the latter still remains large columnar dendrites. The existence of solid solution phase γ-(Fe, Ni) and hard phases of Ni17Si3, Cr5B3, Ni3B in the coating significantly improve the wear resistance of the coating, and the microhardness is nearly 2.5 times higher than that of the substrate. However, the average microhardness of multilayer cladding coating is about 48 HV0.2 higher than that of the single-layer cladding coating. In addition, the fine surface structure of the three-layer nickel-based coating improves the wear resistance of the coating, making this coating with the best wear resistance.

Finite element analysis of effects of dynamic preheating on thermal behavior of multi-track and multi-layer laser cladding

Laser cladding technologies has received wide attention since its low dilution and high deposition efficiency. However, the high cooling rate and the temperature gradient due to the rapid heating and cooling characteristic could cause excessive thermal stress and even crack in the coating. In this paper, a dynamic preheating method, in which an additional heat source is applied to heat the localized region ahead of the moving molten pool, was proposed with the intent of solving these problems. A three-dimensional finite element model was established to explore the effect of the dynamic preheating on the thermal behavior of the multi-track and multi-layer laser cladding. The laser cladding experiment was performed to verify the accuracy of the heat transfer model. The simulated thermal cycle curves are in agreement with the experimental thermal history. The calculated results show that the temperature gradient in the depth direction and the cooling rate decrease with the increasing layers. The appropriate process parameter, such as thermal flux density, interaction time, and preheating distance leads to the decrease of the cooling rate and the maximum temperature gradient. Thus it is illustrated that dynamic preheating is contributed to the reduction of the thermal stress and the cracking probability.

Innovative clothing system for protection against perforation

Opuntia ficus-indica is a cactus species that has a large potential in several applications. Despite its enormous potential, the production process is still a concern. The harvest process is still mostly manual and implies a dangerous exposure of the human being not only to harsh environmental conditions such as high temperatures but also to the big and resistant spines of the Opuntia ficus-indica. To fulfill the lack of suitable protection equipment for this specific activity, emerged a project with the aim of producing an innovative clothing system composed by textile structures that can act as a barrier to spines and glochids without compromising breathability and presenting a suitable fitting, ergonomics and freedom of movements. This paper will focus on the development of a multilayer clothing system in which the outer layer provide protection against perforation and the inner layer acts like a second skin providing thermal comfort and freedom of movement, so the producers can withstand high temperatures. Concerning the inner layer, several textile structures were developed to analyze the impact on breathability, moisture management and thermal regulation. For the outer layer more than 20 fabrics were developed and submitted to laboratory tests to study their perforation and tearing resistance (according to EN 388).Afterward two structures were selected to proceed and new finishing’s were developed to prevent the adhesion of the glochids to the textile substrate and simultaneously to give water repellency. Results achieved for the clothing solution from laboratory and field tests with end-users, will be presented.

Influence of laser cladding parameters on distortion, thermal history and melt pool behaviour in multi-layer deposition of stellite 6: In-situ measurement

Laser cladding is a surface coating technique used to produce high wear and corrosion resistance coatings. The residual stresses and distortion developed during cladding effects the clad mechanical properties, dimensional accuracy and its performance. In this present study, the substrate distortion and thermal history of Stellite 6 were monitored online during mult-ilayer deposition, using Laser Displacement Sensors (LDS) and non-contact Pyrometers. In depth analysis has been carried to investigate the effect of process parameters on distortion and temperature. The results show that, the deflection increases with increase in laser power and decrease in scan speed. The deflection measured was 18–20 % higher when the scanning speed is reduced from 20 mm/s to 12 mm/s and around 30 % more deflection when the laser power is increased to 3400 W from 2400 W. Whereas, the second layer compared to single layer deposition has shown decreased deflection which is due to the low thermal gradient along the thickness. The thermal history of the melt pool shows that the increase in Linear Heat Input (LHI) increases the melt pool life span, thereby inducing more substrate deflection. The results also reflect the formation of strong metallurgical bond and hard carbides in all the samples. The study also provided an optimum set of process parameters that induces minimum distortion in multi-layer cladding of Stellite 6.

Corrosion Behavior of C4 Coating Produced by Cladding Laser in Sulfuric Acid

C4 coating was prepared by high power multilayer laser cladding. Corrosion behavior of the C4 coating and 316 stainless steel in sulfuric acid solution was investigated. The corrosion rate was measured by using the mass loss method. Obvious corrosion morphology and serious exfoliation corrosion of 316 stainless steel are noticed in sulfuric acid solution. While C4 coating after corrosion test shows nearly unchanged surface morphology. The results show that corrosion resistance of C4 coatings is higher than 316 stainless steel. The corrosion morphology was observed by SEM(Scanning Electron Microscope), and the elements distribution of corrosion products was analyzed by EDS(Energy-Dispersive X-ray Spectroscopy).The results show that the S element content increased with the extension of corrosion time, while the Cr content decreased. For the 316 stainless steel, with the extension of corrosion time, the content of C increased. The sulfur-containing corrosion products on the surface are all dissolved in the acid solution. The contents of Cr and Ni decreased, and their passivation ability was weakened. The results indicate that C4 coating exhibits better corrosion resistance in sulfuric acid solution due to the stable formation of dense oxide film on the surface.

Aerodynamics of air-permeable multilayer roof cladding

Currently, design approaches to determine loads on different types of building cladding elements can vary significantly by product type, even though they may have similar geometries. Using the full-scale wind tunnel at the Insurance Institute for Business & Home Safety, external and net wind loads on two discontinuous metal roof systems were measured. The results indicate that cavity pressures in air-permeable multilayer cladding, such as discontinuous metal roofs are approximately uniform across individual panels and closely related across multiple panels which share the same cavity. The testing also showed that peak net loads tend to occur slightly after the peak spatial gradient of the external pressure across the cladding elements. The two types of discontinuous metal roofing products, which have significantly different cavity geometries, have similar ratios between the net and external wind loads with metal shingles having a Ceq value of 0.55 and metal panels having a Ceq value of 0.67. Overall, these experimental results indicate that the peak pressure equalization factor is dependent on the external pressure difference across the cladding, the geometry of the cladding, and the fluid inertia of the cavity flow. The experimental results also show that the peak pressure equalization factor is not dependent on location and wind direction, for panels that are not adjacent to the edges.