Search

Once with the technological development, many variants of improving surface behavior through coating with various materials have emerged. In this paper are studied the microstructure, adhesion to the substrate and the utilization properties of thermal plasma coatings on alloy steel substrate (100Cr6). The samples were obtained by plasma spray from three types of powder, both with the bonding and non-bonding versions: Sample 1 - topcoat of Eutalloy 10112 (Ni-Cr-B-Si-Fe-WC), Sample 2 - bonding layer from NiAlSi and Eutalloy 10112 as topcoat; Sample 3 - NiCrFe topcoat (M42); Sample 4 - bonding layer of NiAlSi and NiCrFe topcoat (M42). The samples were analyzed for microstructural changes both longitudinal and in the cross section (for evaluation of the modifications produced at the substrate - coating interface). The adhesion to the substrate was evaluated by the scratch method, applied both longitudinally and in the cross section of the coatings. The results revealed that all the coatings have a good adherence at the substrate and are suitable for applications where wear resistance is needed

In this paper are presented data on the behavior of six multilayer materials with ceramic foam core, respectively aluminum foam core, in case of exposure to open flame. In order to evaluate the behavior of the six samples, a test stand was carried out and the temperature variation on the surface that was not exposed to the open flame was recorded, in relation to the physic-chemical phenomena carried out in the exposure range.

Obtained by different spraying technologies: in atmospheric plasma spray, High Velocity Oxygen Fuel (HVOF) or laser cladding, the layers of hard alloys with a high content of WC and TiC find their industrial applications due to their high hardness and resistance to wear. Recognized as being a process associated with welding, the arc spraying process is a method applied industrially both in obtaining new surfaces and for reconditioning worn ones. This chapter presents the technology for obtaining ultra-hard layers based on WC and TiC - by the arc spraying process, using a classic spray device equipped with a conical nozzle system and tubular wire additional material containing ultra-hard compounds (WC, TiC). To study both the quality of deposits and the influence of thermal spray process parameters on the properties of deposits with WC and TiC content, we approached various investigative techniques, such as optical scanning microscopy (SEM), X-ray diffraction, and determination of adhesion, porosity, Vickers micro-hardness and wear resistance.

This study addresses the possibility of using expanded glass to obtain elements with low thermal transfer and stable from a geometric point of view when exposed to high temperatures, which may later be part of a fire-resistant multi-layer element. For this purpose, three types of recipes were designed and produced, which are composed of expanded foam glass spheres bounded with polymeric resin. Subsequently, 3 sets of each sample were subjected to baking: T1 (heating to 700°C, maintaining for 3 hours, oven cooling); T2 (heating to 600 ° C, maintaining for 3 hours, oven cooling); T3 (heating to 600° C, oven cooling). The 4 sets of samples (1 set in initial state and 3 sets of heat treated samples) were exposed for 1 hour at direct flame. It was found that the samples maintained their structural integrity and all three types of material ensure a temperature difference between the side exposed to temperature and the unexposed side higher than 200°C (considered satisfactory according to SREN 1363-1 / 2001).

Thermal depositions are very wide spread in the industry of coating techniques. The materials used as coatings for several applications must have the ability to produce a stable, slow-growing surface coating, in order to provide good service behavior. This paper presents a method to increase the wear resistance of steering pump cam, strongly stressed having premature wear effects. The method that the authors use is atmospheric plasma deposition with Ni-Cr-Fe and Ni-Cr-B-Fe powders on steel substrate. It was investigated the morphology and physico-mechanical properties (scratch and micro-indentation analysis). Results showed a comparison between those two coatings with the metallic substrate. It has been found that the deposited coatings have an adherent, dense and uniform layer with a typically molten morphology. By increasing the coefficient of friction we can obtain higher wear resistance and recommend the optimum solution for further researches.

The discs of the intake or exhaust valves are vital organs of internal combustion engines, being subjected to extreme operating conditions, thermal, mechanical and chemical types. One of the goals of researches in this area is related to thermal insulation of the combustion chamber of internal combustion engines, which could enhance their performance in operation. In this article we analysed the microstructural aspects of some coatings obtained from powders with thermal barrier role on specific materials for internal combustion engines valves. There were used as substrate samples of low alloy steels with Si and high alloyed steels with Cr, Ni and Mn. Using the facility SPRAYWIZARD 9MCE for atmospheric plasma spraying, two types of thermal barrier coatings were produced, from powders based on zirconia and alumina. The samples were analyzed in terms of microstructure using the QUANTA 200 3D scanning electron microscope and the X`PERT PROMD diffractometer. Observations were made both on the longitudinal surface of the coating in order to evaluate it and on the cross-section to evaluate the substrate-coating interface, the influence of deposition temperatures on the substrate and aspect/microstructure on its depth. XRD analysis revealed a cubic structure of aluminum oxide, respectively zirconium oxide. The identified morphology is a specific "splat" one for the ceramic coatings. Surface appearance shows tiny pores and cracks specific to the spraying method. The resulted coatings present a significant compactness and adherence to the substrate, which recommends them for further thermal behaviour testing.

Liquid wood is one of the newly discovered green polymer materials, being a biodegradable and recyclable thermoplastic, made from cellulose, lignin and natural additives, currently used in commerce as ARBOFIL, ARBOROM and ARBOBLEND. The applications of this material (aeronautics, automotive, construction, consumer goods etc.) are limited by two major drawbacks: higher weight compared to ordinary plastic materials and low melting point (≈ 175° C). In this work was studied the possibility of changing some mechanical and thermal properties of this material by applying superficial coatings. For this process were prepared specimens from two types of material: ARBOBLEND and ARBOFIL. The resulted samples were analyzed in terms of microstructural changes both longitudinally (in order to evaluate the quality of the deposited layer) and on cross section (in order to evaluate the changes produced at the interface substrate - coating). For this purpose were used the QUANTA 200 3D (FEI, Holland, 2009) scanning electron microscope and the X`PERT PROMD diffractometer (Panalitycal, Holland, 2009). Using the UMTR 2M-CTR Micro-tribometer were evaluated the elasticity modulus of the coatings through microindentation and its adhesion to the substrate through scratch method, applied both longitudinally and on cross section.

Preliminary results on the behaviour of metallo-ceramic system during the cutting process were presented. The ceramic layer was obtained, after sandblasting of the substrate, through air plasma spraying with thicknesses of 30 μm on a steel substrate. Layers are chemically homogeneous, without cracks, pores or crevices. The thin layer (30 μm) present discontinuities with uncovered surfaces were the substrate is near in contact with the environment. Cutting process was realized on marking fiber laser equipment (Boron), of 30 watts’ maximum power and wave length of 1064 nm. There were obtained two different grooves on the test pieces with the following parameters: laser double pass at speed of 500 mm/sec, pulsed laser of 20KHz frequency and the beam power was set at 50% (around 15W) for the first groove) and at 80% (around 24W for the second groove). Structural, morphological and chemical evaluation of the cutting kerf was realized using scanning electron microscopy (SEM, Vega Tescan LMHII, SE detector, 30 kV, 15.5 mm WD) and energy dispersive spectroscopy (EDS, Bruker X-flash) using automatic/element list mode, Point, Mapping and Line features. This analysis highlighted the type of defects along the cut, respectively the phenomena occurring at the ceramic - metal interface.

Nanostructured SnO2 was prepared based on the sol-gel method used in the preparation of crystalline metal oxides. Sol-gel process can be described as a forming network of oxide polycondensation reaction of a molecular precursor in a liquid. Six experiments were carried out. Morphological structures and chemical composition were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) after calcination. It is noted that TEM images show that the spheres consist from nanocrystals, quantitative EDS analysis of the chemical composition shows an absence of the chlorine, which is a desired fact. For structural characterization of the material we used X-Ray Diffraction (XRD). The X-ray diffraction pattern for all samples indicates peaks which are agreeable with standard diffraction pattern of SnO2. The particle size of all samples was in the range of 28-92 nm calculated according to Scherrer equation.

In this study was addressed the problem of the contact stress simulation, generated in the case of the loads applied on thermal spray coatings, by finite element modelling. Starting from the characteristic lamellar morphology of this type of coatings, consisting of splats, voids, oxidized or unmelted particles, the studied layers were assimilated to an anisotropic material. Thus, it was tried to establish the parameters necessary for modelling, so that they define as accurately as possible the studied material. The purpose of this study was to identify the maximum value of the tension developed in the point contact, on the depth of the analysed layer. This value was subsequently used to determine the limit values for in practice use of the coatings.

In this paper, the surfaces of some weakly alloyed steel specimens were covered, by arc spraying process, with a layer of high alloyed steel: 97MXC, using core wires. The technological parameters, used to spray the high alloy steel, were kept constant except for the spray stand-off distance (SOD) which varied on three levels. The research was performed on deposits with a thickness between 0.2-2.4 mm. The microstructure of the deposits, the chemical composition, the physical properties of the layers were investigated by SEM analyzes, X-ray diffraction, microhardness tests and adhesion tests. The porosity of the deposits was determined by optical microscopy. The adhesion of the layer to the substrate was researched by the tensile test. Studies have shown the fact that SOD significantly influences the adhesion and porosity of the deposits. Thus, the increase of SOD determines the decrease of the adhesion of the layer to the substrate by approximately 21.4%, the increase of the porosity of the deposits by approximately 14.2% and variations up to 5% of the microhardness.

This study is focused on obtaining a fire-resistant multilayer material, which includes in the structure a layer with properties of high temperature resistance and low heat transfer. One of the research directions is focused on obtaining such a layer using expanded glass granules with two different dimensional ranges noted with A (1 - 2 mm) and B (0.25 - 0.5 mm). The target layer was realized with the shape of square plates of 50 × 50 mm, with a thickness of 5 and 10 mm respectively, from a mixture of quartz sand with a polymeric resin as bonding agent in which the expanded glass granules were inserted. The following samples were obtained: P5A and P5B (5 mm thick plates), respectively P10A and P10B (10 mm thickness plates). The samples were analyzed both from the morphological point of view (the emphasis being placed on the structure distribution of the expanded glass granules) and from the point of view of the resistance to high temperatures (by indirect exposure at temperatures between 400 - 600 ° C for 3 hours). The satisfactory behavior of the samples during the tests recommends the extension of the researches in this direction, in order to establish the optimal percentage of component elements.

TThe present study is an attempt to observe and evaluate the dry rolling wear behavior [1] of three types of Ni-base coatings on an Amsler type wear machine, against low-alloyed steel discs. The tested coatings were obtained by flame spraying (on the same low-alloyed steel substrate as the discs) using commercial Ni-base self-fluxing powders: 1060-00 and 1355-20 type (manufactured by Hoganas) and JK 586 type (manufactured by Deloro Stelite Co). In order to increase the strength of the layers, the deposition was followed by fusing [2]. The tests were conducted on pairs of coated – uncoated discs at the same load and the same speed in all three cases. In order to evaluate the wear behavior, there were observed and measured the surface roughness and the rolling path profiles. A severe wear regime with adhesion as the main phenomenon was observed in case of the low-alloyed steel discs.

A new cast-iron material was obtained by melting in an induction furnace. The material was microstructural and chemical characterized before and after a wear test. We analyze the chemical composition of the material at macro-scale using a Spark Spectrometer and at micro-scale using Dispersive Energy Spectrometer. Microstructure before and after the external solicitations was observed using a Scanning Electron Microscope. We also evaluate the influence of external force on the dendrites microstructural and chemical modification.

There is the opinion, imprinted by tradition, that only bronze alloyed with tin may be used to build bells, musical instruments or sound transmitters, without the need to bring a scientific explanation. Starting from the physical theory and experimental determination that sound travels only through bodies with elastic proprieties, a study over acoustic white cast iron was proposed. After convincing experiments, it results that white cast irons have good properties for producing and transmitting sound waves. The measurements focused two fundamental aspects, the elastic energy available for producing and transmitting sounds and amortization, resulting that white cast irons can substitute with success bronze with tin or even better properties.

Plasma nitriding has significant advantages: very low running costs (reduced consumption of energy and gases); optimized structure and layers; and nitriding of stainless steels. Plasma nitriding is totally safe and has no poisonous gas emissions and no negative environmental impact. However, conventional plasma nitriding has a number of well-known difficulties, including the direct application of plasma on the parts to be treated, the risk of arcing, hollow cathodes, white layers, non-homogenous batch temperature and the impossibility to mix parts of different geometries in the chamber made this technology to be almost forgotten. In the last years, due to the ecofriendly character of the technology, several atempts were made in order to establish an improvement in this technique in terms of batch damages. Active screen plasma nitriding technology is a new industrial solution that enjoys all the advantages of traditional plasma nitriding but does not have its inconveniences. A comparative study regarding quality surface and formed layer properties between conventional plasma nitriding and active screen plasma nitriding was conducted, in order to highlight the advantages that comes with this relatively new technique.

The paper is a practical study, in which the authors have proposed to improve the reliability in operation of hot work tool steels, used for the manufacturing of seamless steel tubes.There were developed samples of hot work tool steel with different chemical compositions by micro-alloying with Mo. The samples were studied in order to investigate their structure and the relations between the microstructure and in-situ behavior.

After the formation of graphite in molten iron starts its dissolution phenomenon in the liquid metal matrix. The inoculants master alloys FeCaSiMg was mechanically mixed with aluminum, a superficial active element that concentrate on metal matrix - inoculant interface, increasing the graphite surface, which dissolves with greater speed in the liquid metal matrix. In the case of smaller cooling rates (parts with great wall thickness) the former compact – spheroidal graphite inclusions significantly reduces its degree of compactness, which results in the decrease of mechanical strength.

Chemical element silicon, placed in liquid iron behaves differently, through the influence they exert on the metallographic structure. The factors that define their influence are the melt temperature, melting bath temperature variation dynamics, the amount that is inserted into melting bath, chemical shape etc.Refining of metallographic structure was found when FeSi was used with 35% si 73% Si.

In modern practice, more and more multi-layered materials are emerging as response to the ever-changing demands of construction beneficiaries. One of these, a fire resistant multilayer material, is studied in this article. The multilayer material was made in two variants - on support of aluminium foam, respectively ceramic foam, and a ceramic fibre plate was used for the side exposed directly to the flame. On this plate, an Al2O3 ceramic coating with the role of thermal barrier was realized by atmospheric plasma spray method. His influence of was evaluated by comparing the recorded temperatures during the fire resistance tests for both the coated and the non-coated samples.

In this paper we studied the possibility of mechanical processing of a coating produced by atmospheric plasma spray method from nickel-based self-fluxing powder. Two samples were realized from the same alloy type - NiCrBSiFe alloyed with WC, one of which was mechanically processed in the raw state and the other after applying the self-fluxing treatment. Subsequently, their behaviour was observed during the mechanical processing. Both the morphology of the coatings after processing and their mechanical properties (using scratch method) were evaluated.

In order to produce shape memory rings for constrained-recovery pipe couplings, from Fe-14 Mn-6 Si-9 Cr-5 Ni (mass%) powders, the main technological steps were (i) mechanical alloying, (ii) sintering, (iii) hot rolling, (iv) hot-shape setting, and (v) thermomechanical training. The article generally describes, within its experimental-procedure section, the last four technological steps of this process the primary purpose of which has been to accurately control both chemical composition and the grain size of shape memory rings. Details of the results obtained in the first technological step, on raw powders employed both in an initial commercial state and in a mixture state of commercial and mechanically alloyed (MA) powders, which were subjected to several heating-cooling cycles have been reported and discussed. By means of differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and X-ray diffraction (XRD), the thermal behaviors of the two sample powders have been analyzed. The effects of the heating-cooling cycles, on raw commercial powders and on 50% MA powders, respectively, were argued from the point of view of specific temperatures and heat variations, of elemental diffusion after thermal cycling and of crystallographic parameters, determined by DSC, SEM, and XRD, respectively.

The main result and characterizing aspect of the research consists of the effectiveness of novel ZnO-linen fibrous composites synthesized by means of hydrothermal deposition of zinc oxide onto linen fibers, with the assistance of two surfactants. This has a direct implication on the relationship between the morphological, structural and chemical attributes and water vapor sorption-desorption behavior. Methodology consists of the hydrothermal synthesis of zinc oxide onto linen fibrous substrates previously grafted with MCT-β-CD (MonoChloroTriazinyl–β-CycloDextrin) via a hydrothermal process. The morphological, structural and chemical properties of the samples were examined, in terms of a co-assisted investigation system: SEM images for the morphology, EDX analysis for surface composition, FTIR spectroscopy and X-ray diffractometry for structural samples features. Dynamic vapor sorption (DVS) analysis will complete this study. According to the results provided by the characterization technique, the uniformity of the fabric coated with ZnO powder hydrothermally synthesized with assistance of CTAB (Cetyl TrimethylAmmonium Bromide) is better than that of ZnO powder hydrothermally synthesized in the presence of Pluronic P123 and possesses good washing fastness. X-ray diffraction results have indicated that the composites exhibited a more ordered structure and higher water vapor sorption-desorption capacity (obtained by DVS analysis) compared with those of the reference fibrous linen supports.

In the last 5-10 years the process of 3D printing has an incredible advanced in all the fields with a tremendous number of applications. Plastic materials exhibit highly beneficial mechanical properties while delivering complex designs impossible to achieve using conventional manufacturing. In this article the printing process (filling degree, time, complications and details finesse) of few plastic elements with complicated geometry and fine details was analyzed and comment. 3D printing offers many of the thermoplastics and industrial materials found in conventional manufacturing. The advantages and disadvantages of 3D printing for plastic parts are discussed. Time of production for an element with complex geometry, from the design to final cut, was evaluated.

In this paper we present the results tribological obtained in the course of dry wear tests on samples coated with three types of coatings produced from self-fluxing Ni-based powders. In this purpose were used three commercial NiCrBSi powders produced by various manufacturers, which have been sprayed against a low alloyed steel substrate using the flame spray thermal deposition method followed by flame remelting, resulting three different samples, denoted as: A, M and P. The first test was conducted on an Amsler type machine, with rolling motion between tribological contacts of third class. The analysed coating was deposited on the generator of the low alloy steel disc and the shoe was realized from a grindstone. The test was conducted for two situations: (a) constant load of 10 kg and 6 kg applied for 5 hours; (b) progressive load starting from 2 to 10 kg for two different speeds of rotation of the disc. The second test was the one of sliding wear and it was conducted on the UMTR 2M-CTR tribometer. The analysed layers were deposited on the flat surface of a low alloy steel lamella, and the friction was achieved with a conical grinding stone. The working parameters were as follows: 20N constant load, constant speed of 10 mm / s, sliding linear length of 30mm, the test duration being 45 minutes. After conducting the tests and after analysing the results, the following conclusions are drawn: a) during the first test has been obtained a global friction coefficient between 0.3 and 0.4 - typical for dry friction, highlighting some lower values in the case of sample A, in which case there were recorded smaller mass losses; b) at the second test was recorded an approximately linear behaviour of the three samples, with a gradual increase of the friction coefficient and a superficial wear mark revealed both by SEM microscopy and by profilometry.

This paper presents, based on a case study, the analysis of the factors that influence the mechanical cyclic fatigue resistance of two grades of low alloy steel with Mo and Cr. It was studied the fatigue behavior in real operating conditions of some active elements manufactured from the two low-alloyed steel grades, elements that are equipping some farm implements. Using the fractographic analysis, optical microscopy and scanning electron microscopy, were analyzed the samples that carried away because of the fatigue fracture. On samples taken from the two brands of low alloy steels with Mo and Cr were performed tempering thermal treatments that modified the structure, in order to improve the operating characteristics. The effect of those thermal treatments was initially observed by microstructural analysis of metallographic prepared samples (by polishing and chemical attack using nital reagent), that revealed a troostite type structure. On the heat-treated samples were determined a number of mechanical properties: hardness, impact strength and tensile test. There was observed an improvement of the impact bending strength for both alloys and a tensile behavior that favors increasing resistance to fatigue.

Because the surface engineering is becoming an increasingly viable alternative to the constructive changes made to improve the efficiency of internal combustion engines, have been proposed and tested various types of coatings of some organs of internal combustion engines. One vital organ is the engine valves, which is subjected during operation to combined thermal, mechanical, corrosion and wear solicitations, which are leading to severe corrosion and complete breakdown. In this paper were analyzed aspects of valves wear and the active surfaces were coated using the atmospheric plasma spraying method (APS) with two commercial powders: Ni-Al and YSZ. Microstructural analyzes were made on these layers and also observations regarding the possibility of using them as thermal barrier and anti-oxidant coatings.

Due to the development of thermal spray deposition technologies, thus obtained layers have more applications and fields of use. One of the coatings with increased application is the one produced from Ni-based self-fluxing alloys, which besides the good wear resistance, shows a satisfactory corrosion resistance. In this study it was observed the behavior of three types of coatings produced by Flame Spray method, both at wear and especially corrosion in the environment simulating acid rain. As a result of the experiments it was found that these layers became compact enough after applying the self-fluxing heat treatment, so in their structure are not present defects such as pores and micro-cracks, unmelted particles etc., which could be points of corrosion initiation.

Some metallic materials exhibit good damping capacity of mechanical energy into thermal energy. This property along with the others metallic characteristics make this materials interesting for a big number of applications. These materials can be used as bumpers in different applications including automotive field. Beside grey cast iron and shape memory alloys few new metallic materials are presented for the supposition of high damping capacity. We analyze the causes that increase the internal friction of some metallic materials and possibilities to enhance this property through different mechanical, physical or chemical methods. Shape memory alloys, especially those based on copper, present a different damping capacity on martensite, austenite or transition state. In the transformation range M ↔A, which in case of copper base shape memory alloys is quite large, the metallic intelligent materials present a high internal friction, almost comparable with natural rubber behavior that can transform mechanical energy into thermal energy till a certain value of the external solicitation. These materials can be used as noise or small vibrations bumpers or even as shock absorbers in automotive industry.

Zirconia (ZrO2) as a ceramic biomaterial facilitates the osteoconductivity in new bone formation around implant. In order to improve the degradation and the surface properties, it is necessary to apply a surface film to satisfy multiple clinical requirements such as mechanical strength, biocompatibility, and degradation rate. Therefore, surface changing to form a tenacious, biocompatible and corrosion resistant modified layer has become a necessary study in biodegradable materials. The aim of the study is to observe the morphology, structural and scratch analysis for some coatings of ZrO2-CaO and ZrO2-Y2O3 having similar thickness deposited with an atmospheric plasma spraying facility, Sulzer Metco 9MCE, using scanning electron microscopy and X-Ray diffraction. Some mechanical aspects were highlighted during the scratch test. Comparative scratch tests were carried out to study the bonding properties between the coatings and the substrates.