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Electronic components soldered with tin base alloys are subject to whiskers formations after an operation period, which produced failures by short circuits. The main factors which determine formation of whiskers are soldering alloy characteristics, substrate alloys which is placed on the surface of the PCB boards and not the least the working environment. Soldering alloy has a major influence on germination and growing whiskers process, by its nature and grain form, dimensions and orientation. Given the preliminary research carried out to diminish the formation of these defects, was proposed to realize these soldered joints using new soldering alloys obtained by melt-spinning method, which have a nanocrystalline, quasi-crystalline or even amorphous structure. In this paper are presented some results obtained on following the influence of soldering alloy structure over whiskers germination and growing process, by simulating the operation conditions according to applicable standards. Were obtained soldered joints on copper plates using a commercial soldering alloy as well as soldering alloys base on Sn-Cu-Ga, Sn-Cu-Ni, Sn-Cu-CO families, obtained by melt-spinning method. Soldering was performed using a soldering iron and after this process, the soldered joints were placed in an incubator under controlled temperature and humidity conditions. Performing SEM analyzes on soldered joints subject to the above treatment, was observed that formation and growing of whiskers diminished with decrease of the grain size.

The aim of the current study is to perform a failure analysis on specimens extracted from 4 mm sheets of AZ31B, according to ASTM 4377G and 3 mm sheets of Cu99 alloys according to SR EN 1652:2000, that were joined together using FSW and FSW-IG processes. In order to promote the suitability and advantages of implementing FSW-IG processes in the automotive and aerospace industry, the papers authors performed destructive testing on the samples extracted, namely tensile strength test, following with topography analysis using scanning electron microscopy – SEM, combined with energy dispersive spectroscopy EDS, micro-hardness tests and fractography investigations. Results highlighted a considerable improvement in the ultimate tensile strength of the welded joint, a higher degree of deformability of the welded joint in the case of FSW – IG, compared to classical FSW; while maintaining the same process conditions and parameters. Experimental data is in accordant with automotive and aerospace imposed compliances, thus presented and discussed in the following scientific article.

Ribbons having the chemical composition Cu48Zr47Al5 and Cu45Zr45Al5Ag5 were made using the melt spinning technique in an open environment. Making a product, in this case glassy ribbons, on a large scale is fitting if the process and materials are not costly hence controlled atmosphere was not used for the melt spinning technique. In this paper such a trial was done to check how adding Al and Al-Ag changes the structural and mechanical properties of Cu-Zr alloys. The structure, GFA (glass forming ability) and hardness were analyzed using X-ray diffraction, differential scanning calorimetry, Vickers-type hardness. Also, the GFA was estimated with the help of a series of different parameters (e.g., supercooled liquid region).

Over the past decade, metal oxides are of great interest in many fields due to their properties as semiconductors. Heterostructure based on Cu-Zr mixed oxide are very promising due to their broad absorption region, making them favorable materials for photocatalysis and photoelectrodes in solar cells applications. The production of metal oxides by oxidation of amorphous ribbons is a relatively simple process that allows a good control over the size and shape of the metal oxides crystals. In this study we used amorphous ribbons from a ternary alloy Cu48Zr47Al5. The small percentage of Al in the alloy component aims to improve the semiconductor performance, working as a dopant in the metal oxide heterostructure. In order to investigate the structural and morphological properties of the obtained metal oxide heterostructure, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used, along with ultraviolet–visible spectroscopy (UV–Vis) for determining the modified absorption regions as well as the band gap value.

Amorphous alloys exhibit random atomic arrangements in solid state form, and the phenomena of segregation and grains boundaries are absent. These alloys are obtained by rapid quenching techniques of the melt, with cooling rates of 105 … 106 ℃/s. As a result of the requirement of an extremely high cooling rate, their delivery forms are usually limited to thin films, thin ribbons and, powders. The resistivity of amorphous metals does not depend on temperature as in the case of crystalline ones, exemplified in a situation in which a Pd76Si20Cr4 alloy was heated to a temperature of 4000 K and it was observed that the resistivity in the case of the amorphous alloy increased 3 times higher than in the case of the crystalline alloy. The chemical composition of the processed alloy, in which Si and B are added to stabilize the amorphous phase, leads to an electrical resistivity of 1.72 × 10−6 Ωm and an electrical resistance of 2.9 Ω, which is 3 times higher than that of the Ni-based crystalline alloy, from which the electrical resistances are manufactured.

With the evolution of society new materials or classes of materials must be developed. The metallic alloys with amorphous structure have exceptional physical properties due to the spatial order of the atoms in structure and the absence of crystalline defects such as dislocations, grain boundaries, etc. Due to the metastable states in which these alloys are located, obtaining bulk materials from amorphous metal alloys is difficult, being limited to simple geometries and high production cost. This problem can be solved by using the ultrasonic welding of amorphous ribbons for the production of bulk metallic glasses.In this paper, we aimed to produce bulk metallic glasses materials by welding the ribbon packages in ultrasonic field. In order to prove the preservation of the amorphous structure of both the primary welding alloys as well as after the welding of the amorphous ribbons, Differential thermal analysis (DTA), X-ray diffraction (XRD), Scanning electron microscopy (SEM) analysis were carried out. Vickers micro-hardness test was also performed in order to reveal the mechanical properties in the welded joint.

This paper presents experiments regarding the welding with electron beam of multiple overlapping Ni-based amorphous ribbons produced by "Planar flow casting" method [1]. Welded samples were performed, using the electron beam welding equipment “Chamber Machine EBG 45-150 K14” [2]. The welded joints were analyzed by SEM, EDX, XRD in order to optimize some technological parameters to avoid deterioration of the amorphous ribbons during the welding process [3].

The dual amorphous phase bulk metallic glasses (DAPBMGs) contain two distinct amorphous alloys in order to bring together all the favorable properties of each phase. A viable method for obtaining dual bulk amorphous alloys is powder metallurgy. A Zr/Fe DAPBMG were successfully prepared by hot-pressing of Zr –based and Fe –based glassy alloy powder in different volumetric proportions. The samples obtained were structural investigated by scanning electron microscopy and X-Ray diffraction. Magnetic properties were determined using hysteresis graph of integrator fluxmeter type. It was found that with increasing the volume ratio of the Fe-based alloy decreases the coercivity and increases saturation magnetization

The bulk metallic glasses composites are a new class of bulk metallic glasses (BMGs), containing an amorphous metal matrix and reinforcing materials of metallic or ceramic nature in order to obtaining the desired combination of mechanical properties including strength, hardness, ductility and toughness. Composite materials of cylindrical form with the diameter of 10 mm and 5 mm in height were successfully prepared by hot-pressing of Zr - based glassy alloy powder and Fe - based nanocrystalline alloy powder in different volume fraction. The samples obtained were structural investigated by scanning electron microscopy and X-Ray diffraction and mechanically characterized by hardness and compression tests. It was found that increasing the volume ratio of the Fe-based nanocrystalline alloy up to a certain value leads to an increase in hardness and mechanical compressive strength.

Bulk metallic glasses (BMGs) represent a viable alternative for replacing classic materials used in medical devices. This paper presents the research conducted in order to obtain copper based BMGs using two different chemical compositions: Cu48Zr47Al5 and Cu45Zr45Al5Ag5. The samples were obtained by copper mold casting and their structure and properties were investigated using X-Ray diffraction (XRD), differential scanning calorimetry (DSC) and optical microscopy.

Soldering electronic components with Sn-based alloy may lead to an occurrence of defects of which the most dangerous are the whiskers growths. These whiskers growths are crystalline structures that grow spontaneously in the solder alloy and cause a short circuit in PCBs (Printed Circuit Boards). An important factor that favors the appearance of whiskers growths is the internal stress that occurs in the solder alloy. The higher the state of compression stress is, the higher the risk of growing whiskers. By X-ray diffraction, the internal stresses were calculated in the case of two soldered joints made by the reflow method. The first joint was performed with a commercial solder alloy Sn99Ag0.3Cu0.7, and the second one with the nanocrystalline structured alloy Sn95Cu2Ga3, obtained by the melt-spinning method. It was found that the value of the compression stress determined in the case of soldering with Sn95Cu2Ga3 alloy is about 12 times lower than the value of the compression stress calculated in the case of soldering with Sn99Ag0.3Cu0.7 alloy. In conclusion, a significant grain finishing of the solder alloy reduces the risk of whiskers growths.

Increasing attention has been drawn lately to the biomedical application of BMGs. Successful rods of 3mm diameter...

This paper investigates the effect of temperature on the microstructure, failure mechanism and compressive mechanical properties of newly developed ZA27 syntactic foams. Two different types of filler particles are considered, i.e. expanded perlite (P) and expanded glass (G). Metallic syntactic foam (MSF) has been produced via a counter-gravity infiltration process of packed particle beds, followed by controlled thermal exposure. Quasi-static compressive tests were carried out on cylindrical samples at five different in-situ testing temperatures between 25 °C and 350 °C. At all considered temperatures, P-MSF exhibits superior mechanical properties compared to G-MSF. The mechanical properties of both foam types decrease significantly with increasing testing temperature. For comparison, solid ZA27 samples were compressed at the same testing temperatures. Due to microstructural changes, a significant strength degradation of solid ZA27 was observed starting at 100 °C. Comparison of results indicates that the temperature-dependent mechanical properties of P-MSF and G-MSF are strongly controlled by the matrix material. However, the addition of particles decreased the relative reduction of plateau stress and volumetric energy absorption of ZA27 MSF at elevated temperatures.

This paper presents experiments regarding the welding with electron beam of Ni based amorphous ribbons produced by "Planar flow casting" method with the aid of "Politehnica" University of Timisoara equipment. Welded samples were performed in partnership with Graz University of Technology, Institute of Materials Science, Joining and Forming, using the electron beam welding equipment “Chamber Machine EBG 45-150 K14”. The welded joints were analyzed by SEM, EDX, XRD in order to optimize some technological parameters to avoid deterioration of the amorphous ribbons during the welding process.

Bulk amorphous steels (BASs) are a novel class of Fe-based bulk metallic glasses (BMGs), which have an attractive physical, thermal and mechanical properties that make them suitable for lots of industrial applications [1-3]. BAS synthesis requires special preparation conditions such as vacuum or controlled atmosphere and high-purity raw materials. These obtaining conditions increase the cost of these alloys and thus limit the development of new industrial applications. Multicomponent BAS rods with a diameter of 3 mm and 40 mm in length have been obtained by water-cooled copper mold casting in an air atmosphere, using industrial ferroalloys as raw materials. The obtained samples were structurally characterized by X-ray diffraction (XRD) and differential scanning calorimetry (DSC), while the mechanical properties were investigated by hardness and compression tests. Resulting structural aspects and mechanical properties are reported.

Amorphous gray iron ribbons can be used as reinforcement fibers in the manufacture of composite materials due to unique combination of high yield strength and a high hardness with good ductility. Amorphousribbons with the thickness of 20 μm and width of 1.5 mm of Fe73Cr8PxSi12-xC7 (x = 9, 10, 11)alloy were prepared by melt-spinning method. The elaborated alloys were structurally investigated by X-Ray diffraction (XRD) and differential scanning calorimetry (DSC), while the mechanical properties were investigated by tensile micro hardness and bending tests. It was found that increasingP content up to 10 atomic percentages led to a brittle material.

Brazing alloys with amorphous structure have excellent technological properties (tensile, wetting), having a self-fluxing character. The brazed joints have good mechanical and corrosion resistance. In this work an amorphous alloy, ribbon form, for brazing of copper pipe components, was elaborated. The brazed joints were analyzed by optical and electronic microscopy. The brazing alloy is self-fluxing and has good tensile and wetting properties. The structure in the brazed joint is monophasic due to the optimization of the process parameters (voltage and brazing time).

In this study the behavior of brazing joints with nickel-silicon-based amorphous alloys ribbons was analyzed in terms of mechanical strength and corrosion resistance. Two Ni78Si8B15 and Ni68Fe3Cr7Si8B14 metallic glasses ribbons designed and fabricated in our laboratory have been studied as brazing foils. The base material of the joint is the 316L austenitic stainless steel. Note that the two tested chemical compositions of the ribbons are recommended for brazing stainless steels. A comparison between brazed joints and welded steel by electrical resistance spot has also been conducted. As results, Ni78Si8B15 amorphous alloy presents a very good castability, wettability and flowability. However the addition of chromium and iron to form Ni68Fe3Cr7Si8B14 significantly increases the melting temperature, the corrosion resistance and the mechanical strength. Finally we found that the brazed joint with Ni68Fe3Cr7Si8B14 metallic glasses ribbon has the same yield strength than that of the welded joint, but it presents a better corrosion resistance.

Friction Stir Welding (FSW) is an innovative solid state welding process, relatively new in industry, which allow welding of two or more materials which have very different properties, particularly thermal properties as fusion temperature, thermal expansion coefficient, specific heat and thermal conduction and have a predisposition to form intermetallic brittle phases, neither one of the components to be weld reach to the melting point. Being a solid state welding process temperature field is very important for the quality of the welded joint, and a lot of researches focused on this topic. This paper presents some results in modeling and estimation of thermal field developed during FSW of dissimilar joints, using Finite Element Analysis. Numerical modeling of thermal field allows engineers to predict, in advance, the evolution of temperature and to estimate the behavior of the welded materials during the welding process. This will reduce significantly the time and number of experiments that have to be carried out, in the process of establishing a good FSW technology, as well as reducing significantly the cost of the tests.

Metallic amorphous materials were developed during 80’s as new materials, with very interesting industrial properties (heat conductivity, magnetic properties, fusion temperature, corrosion resistance, etc.). Technology to obtain these materials, based on very rapid cooling of a melted alloy with glass forming ability, has limitations for the dimensions of the products that can be obtained with amorphous structure (thickness has to be very thin), which can be overpassed by development of bulk amorphous alloys with high glass forming ability and good control of the cooling speed. Numerical modeling of thermal field during ultra-high cooling, developed in researches presented in this paper, allows researchers to estimate the results of applying in reality certain cooling conditions. This model will help developers of bulk amorphous alloys in checking if are ensured conditions to obtain an amorphous alloy with fewer experimental tests, less time and low expenses.

In order to be competitive, it is demanded to have thin, tough and long lasting coatings. An important aspect is to use stable deposition technologies. As Cr assures wear, corrosion and high temperature resistance, the most employed coatings in industry generally contain Cr. Nevertheless, Cr is a hazardous element for the humans’ health, therefore, sustainable alternatives are needed to be implemented. The aim of this work is to investigate the microstructure, hardness, corrosion resistance and wear behavior of the novel WC-CoMo compared to conventional WC-Co coatings. So far, WC-CoMo coatings are not part of state of the art regarding the Atmospheric Plasma Sprayed (APS) coatings. WC-Co powder in plain form and mechanically mixed with Mo was deposited using the APS method on standardized Type A Almen Strips (C67 steel). The size of the powder grains varies between 5 µm and 30 µm. The obtained samples were investigated by means of Scanning Electron Microscopy, Energy Dispersive X-Ray Spectroscopy, X-Ray Diffraction, and hardness, wear and corrosion behavior were also evaluated. Results revealed formation of different intermetallic phases around the WC particles, which have a benefic influence on the coating characteristics and microstructure.

The actual state of technological development needs to extend the brazing field of stainless steels and non-ferrous alloys based on Cu, Al, Ni, Co, Ti in leading industries, such as aerospace, energy, chemical, etc. The brazing process is influenced by a large number of parameters, which affects the quality of the joint. This paper presents a mathematical model of resistance brazing process of copper-stainless steel using a factorial experiment. The parameters considered important and which will be analyzed during this experiment are the brazing current, time and force. The output data is given by the quality of brazed joint, represented by shear strength. The objectives of this experiment are establishing the Pareto chart of the effects, the main effects of the parameters, how the response changes during the experiment when each of these factors is changed, and process optimization.

In this paper will be presented experimental researches on development advanced alloys with amorphous structures based on Ni and Cu for resistance brazing joints. The main advantages of these amorphous alloys in shape of ribbons are their ductility and flexibility. These ribbons are obtained by ultra-rapid cooling of the melt. Using resistance brazing process, were obtained brazing joints of stainless steel and copper strips. The joints were mechanical and structural analysed. It was performed mechanical shear test on the brazed joints to establish the shear strength of the joints, and also it was performed structural investigation to emphasize the microscopic structure and the structural transformations that take place in the base material and brazing alloys during the brazing process.

Scratch test is one of widely used, fast, and effective methods to obtain the critical loads that are related to adhesion properties of coatings. The determination of adhesion and the scratch resistance is essential for the mechanical characterization of surface layers for research and industry. To evaluate the performance of coatings the scratch test with a Rockwell-C diamond stylus as indenter is a commonly used test for the characterization of hard coatings on predominant metallic substrates due to its comparatively robust experimental setup, the easy use and the representative results. This is the only technique capable of imaging such interface defects which are due to the stressin duced by the scratch experiment.This paper aims to characterize the adhesion and scratch resistance using Millennium200 - Technical Tribo equipment of Ti layer deposited on steel surfaces by means of TIG/WIG welding technique. Ensuring appropriate functional properties of WIG welding coatings (Ti) requires a good compatibility with the substrate material (S235). For this reason was used to deposit titanium WIG welding an intermediary layer of copper, obtained in the same experimental conditions. The optimal selection of the coating material takes into consideration the metallurgical, mechanical and process technology compatibility. The mechanical properties of coatings must match the substrate. From this point of view, maintaining a high corrosion resistance is mainly conditioned by achieving a good adhesion and a microstructure free of internal cracks or other defects.

The joining of the galvanized sheet is normally difficult to be done with classical methods, requiring special attention to the specific problems involved during the welding process. This paper presents the development of the joint technology by Cold Metal Transfer (CMT) of galvanized steel sheet using as filler material a CuSi wire electrode. The salt fog corrosion test was made to certify anticorrosive protection of the galvanized sheet metal joints. This test revealed a minimal deterioration of the galvanized zinc coating during welding and also confirms that using adequate technology galvanized steel can be weld without affected anticorrosive protection of the zinc layer.Experimental researches include optimization of the welding technology using CMT concept; technical skill development solutions of the joints; elaboration and implementation of laboratory advanced technology; experimentation and demonstration of technology functionality by obtaining of braze welded joints corrosion resistant.

Ni based amorphous alloys with Si and B, which can also, contains Fe and Cr, prepared by rapid solidification, have low melting temperatures. This fact increases their susceptibility to be joined by welding and brazing. The glass forming ability (GFA) is conditioned also by the crystallization delay, due to certain chemical composition of the alloys. The thermal stability of these alloys was revealed by DTA analysis and structural characteristics were investigated by XRD. Applying an annealing at temperatures between 420°C and 540°C, with 30 minutes maintaining time, allowed the investigation of phase occurred during the crystallization and the estimation of the crystalline grains dimensions.

Components soldered with Sn-based alloys are susceptible to the growth of whiskers. Tin whiskers have been proven to be responsible for equipment failures in a wide range of industries. In order to reduce defects in electronic components a new solder alloy is proposed based on the Sn-Cu alloys. The Sn-Cu-Ga alloy utilised in this study was fabricated as a ribbons using melt-spinning method. These ribbons were then soldered onto electroplated tin layers. Preliminary characterization of the solder alloy is presented in this paper, including scanning electron microscopy, EDX mapping and X-ray diffraction. Key words: tin whiskers, PCB, printed circuit boards, melt spinning, solder, ribbons

Development of Fe-based bulk metallic glasses (BMG) with good mechanical and soft magnetic properties has become a major objective in the materials science field. Bulk metallic glasses present an interesting combination of properties. They exhibit very high strength (both in tension and compression), large elastic elongation limit, high hardness, excellent corrosion resistance, and good soft magnetic properties. These properties makes them suitable for many applications like high resistant control cables, pressure vessels, micro-components, pressure sensors, microgears for motors, magnetic cores for power supplies and hard fibers in composite materials. Multi-component Fe60Co14Ga2P10B5Si3Al3C3bulk metallic glass was synthesized in rod form with a diameter of 1 mm by copper mould casting technique using raw industrial materials. The obtained alloy was analyzed by X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM) techniques, in order to determine the phase constituent, the thermal stability and the fracture surfaces of as-cast samples. The mechanical behaviour was investigated by microhardness and compression tests. The values recorded for hardness and fracture strength includes this alloy in the category of high resistant materials.

Based on the relation proposed by Tabor in 1951, which connects the ultimate tensile strength and the yield stress of classical materials to the Brinell or Vickers hardness numbers by a simple factor of proportionality, we propose an extended analytical model for the determination of the yield stress of brittle materials using nanoindentation data. This model considers the nanoindentation hardness calculated from the projected actual contact area between the indenter and the material which is representative of the real mean pressure exerted by the indenter compared to classical hardness numbers. A coefficient is introduced in the model to integrate the extent of the elastic recovery of the indented material occurring after the withdrawal of the indenter. This is possible by using the criterion defined by the residual to maximum indenter displacements ratio, this criterion being already related to the deformation mode under indentation. Indeed, this criterion allows identifying the piling-up deformation observed for complete or fully plastic deformation materials or the sinking-in deformation for purely elastic materials. The proposed model thus allows a good estimation of the yield stress of brittle materials for which classical tensile tests are not applicable. The model is validated on a variety of amorphous nickel–silicon-based alloy ribbons, i.e., Ni 89 Si 9 B 2 , Ni 78 Si 9 B 13 and Ni 68 Fe 3 Cr 7 Si 8 B 14 on which both nanoindentation tests and tensile experiments have been performed.

Nickel based amorphous alloys have been developed in ribbons form by planar flow casting method and were subjected to tensile tests. For this purpose, specimens with calibrated area were obtained by electroerosion cutting method and tested at tensile test with different strain rates. Following the results obtained during the tests, the mechanical properties have been determined and compared and the fracture behaviour has been analyzed by scanning electron microscopy.

Metallic bipolar plates have the advantages of better manufacturability, higher strength over graphite bipolar plates. The higher strength and toughness of the metallic materials permits the reduction of the width of the bipolar plate so, the volume and mass of the fuel cell can also be reduced. In this paper we are investigating the use of Ni-based amorphous material as a bipolar plate for polymer electrolyte membrane fuel cell (PEMFC). The major requirements of the metallic bipolar plate material are low weight, high corrosion and low contact resistance. The corrosion property of the present alloy has been investigated under conditions that simulate the fuel cell environment. Hydrogen gas and air were bubbled into a 1 N H2SO4solution at 70 °C, throughout the experiment to simulate the respective anodic and cathodic PEMFC environment. The Ni-base amorphous alloys displayed higher corrosion resistance than stainless steel.

This paper presents some results for numerical simulation of the thermal field developed during rapid cooling of iron base alloy (Fe73Cr2Ga4P13Si5C3), to obtain bulk metallic glasses. Technology of rapid cooling gives the possibility to obtain bulk metallic alloys with an amorphous structure which can be used for industrial applications like magnetic shields. Validity of the numerical model of the cooling process was confirmed by the X-ray diffraction analysis. Once the model being validate, it can be used to optimize the rapid cooling process and casting mold geometry to be able to investigate the possibility to obtain larger amorphous bulk components.

Nickel–titanium- group 5A metal (V, Nb, Ta, Zr) alloys are known as promising hydrogen-selective membrane materials. They can potentially be used in membrane reactors, which can produce high-purity H2 and CO2 streams from coal-derived syngas at elevated temperatures. The master alloys were prepared by arc melting using high purity metals in a Ti-gettered argon atmosphere. The alloys were melted several times in order to improve homogeneity. The ingots were induction-melted under a high-purity argon atmosphere in a quartz tube and graphite crucible injected through a nozzle onto a Cu wheel to produce rapidly solidified amorphous ribbons. Thermal stability of the Ni40Ti40Nb20 and Ni32Ti48Nb20 thin tapes has been examined using DTA analysis.

This paper presents a mathematical model that describes the influence of the chemical composition on the glass forming ability of ferromagnetic alloys. Glass forming ability is given by the difference between the glass transition temperature and the primary crystallization temperature of the alloy. The glass forming ability is better as long this difference has a higher value. These temperatures were determined using differential thermal analysis.

International audience; A methodology for obtaining a nanocrystalline Al91-Mn6-Nd3 alloy and characterizing its mechanical properties is presented. The fabrication procedure, based on the melt spinning method, allowed the preparation of thin ribbons of not, vert, similar30 μm in thickness. The hardness and elastic modulus have been determined by classical and instrumented indentation tests considering the influence of the ribbon thickness on the indentation measurements. The Martens hardness has been calculated by means of instrumented indentation tests, for which the fixing support of the sample has no influence on the indentation measurement. The results have been subsequently compared with those obtained from classical Vickers hardness measurements, for which some composite hardness models have been applied in order to separate the contribution of the fixing support to the hardness measurement. It has been concluded that both methodologies lead to similar values for the mechanical properties of the alloy, i.e. not, vert, similar3.4 GPa for the macrohardness and not, vert, similar3.8 MPa m1/2 for the hardness length-scale factor of the material. The elastic modulus of the material, resulting from the analysis of the unloading indentation curves, has been found to be not, vert, similar131 GPa.

The corrosion behavior of High-Velocity Oxygen Fuel (HVOF) sprayed MCrAlY coatings obtained from CoNiCrAlY particles (wt. 8% Al) mechanically doped with Al2O3 nanopowder was investigated before and after laser remelting. The latter process was applied in order to achieve a homogeneous structure as well as better mechanical properties for the coating (reduced brittleness offered by the presence of the Al2O3 nanoparticles). Another important task of the laboratory investigations was the investigation of the corrosion behavior of the modified coatings. The results obtained from the potentiodynamic polarization measurements carried out in a chloride environment revealed an enhanced corrosion resistance of the laser remelted coatings comprising a refined microstructure. Microhardness measurements of the modified coatings revealed lower values in comparison with that of the samples in as-sprayed status. This observation leads to the assumption that a concomitant improvement of coatings ductility occurred as well.