Mircea Horia Tierean

The Effect of Laser Shock Processing on Corrosion Resistance of Stainless Steel AISI 316L

The paper presents the effect of laser shock processing on stainless steel 316L corrosion resistance. The samples were laser welded and mechanical treated using a Nd:YAG laser with a 1064 nm wavelength, and two different pulse density: 900 pulse/cm2 and 1600 pulse/cm2. After the laser shock processing, the samples were subjected to a seawater solution for corrosion testing. The curves obtained were statistically modeled using Stern-Geary equation. One may observe that the corrosion speed of the LSP samples treated with 900 pulse/cm2 is eight times higher than the corrosion speed of the LSP samples treated with 1600 pulse/cm2.

Carbon Nanoparticle-Supported Pd Obtained by Solar Physical Vapor Deposition

Palladium supported on carbon nanoparticles has been obtained on a specially designed ceramic catalyst, obtained by thermal spraying on a copper substrate, starting from Pd/C targets. Solar physical vapor deposition in argon, an environment-friendly and energy-efficient alternative to arc or chemical vapor deposition, has been employed as a means of target vaporization at CNRS-PROMES facility in Odeillo, France. The obtained nanoparticles have a spherical-porous morphology with diameters ranging from 50 to 120 nm and specific sorption areas of 50,000 m2/g. The XRD diffractograms indicate the presence of dominatingly crystalline short-range ordered graphene oxide layers, in contrast with the amorphous Pd/C starting precursor. The presence of palladium (0.6% wt.) at the surface of the nanoparticles was proved by the EDX and XRD analyses, making the synthesized material useful in applications such as catalysis or gas sorption.

Thermal and Thermorheologic Characterization of Different Polyolefin Waste Fractions

In this study, melt flow index values from several household waste fractions containing mainly polypropylene and high-density polyethylene, were measured at 190 °C for polyethylene and 230 °C for polypropylene-rich fractions. High values of MFI (low shear viscosities) have been reported probably due to the lower molecular mass of the polymer waste and/or the presence of surfactant compounds on the surface of the polymer flakes. Also, by extruding the same batch in different cycles at the same temperature values, the number of processing cycles on which the polymer could be recycled has been determined.

Mechanical Properties and Microstructure Aspects of AlSi10Mg Casting in Vibrating Field

Aluminum alloys are one of the most extended groups of functional materials by reason of combination between good mechanical properties and low mass. The aim of the present paper is to test the influence of the vibrations on the AlSi10Mg (EN 1706-2010) solidification. For comparison, six lots were casted in cold and preheating molds, with or without vibrations within 50 Hz and 1050 Hz. For each casting frequency was measured the silicon phase dimension, hardness, tensile stress and impact strength. The mechanical properties increase with the vibration frequency. Increasing the vibration frequency, the structure will be refined and also the size of the silicon phase is decreasing. Considering that one source of porosity is the gas entrapped or dissolved in the liquid metal during the casting, using vibration along casting and cooling allows it’s decreasing.

Pulsed Laser Cladding of Ni Based Powder

The aim of this paper is to optimize the operational parameters and quality of one step Metco Inconel 718 atomized powder laser cladded tracks, deposited on AISI 316 stainless steel substrate by means of a 1064 nm high power pulsed laser, together with a Precitec cladding head manipulated by a CLOOS 7 axes robot. The optimization of parameters and cladding quality has been assessed through Taguchi interaction matrix and graphical output. The study demonstrates that very good cladded layers with low dilution and increased mechanical proprieties could be fabricated using low laser energy density by involving a pulsed laser.

Characterization of Fusion Lines Obtained with Laser Welding on Ductile Iron Plates

This paper studies the ductile iron (DI) weldability using laser welding. For performing an Yb:YAG continuous laser was used, with a maximum power of 6 kW. The parametrical window power (P) - welding speed (S) was explored by carrying out the fusion lines on ductile iron plates without preheating, to determinate areas of weldability (complete penetration, correct geometry) to allow further characterization. The criteria for selection of focus areas were the geometry of the fusion lines and the absence of the welding defects. The unsatisfactory domains were characterized by: collapse of the melted metal, incomplete penetration, low fusion lines quality (geometry, compactness). In present study, several values of power and welding speed have been tested to identify their influence on geometry, compactness of the joints and mechanical properties. As result, the power-welding speed diagram for feasible domains of laser welding was generated.

A Comparison of Flame Coating and Laser Cladding Using Ni Based Powders

This paper addresses to the characterization of Ni based coatings realized by two different processes e.g. thermal spray coating and laser cladding. For the relevance of the experimental tests, the same base material, AISI 5140 and Metco 15E powder was used. The results highlight the advantages and disadvantages of the both techniques. The cladded layer obtained through laser cladding is pore and crack free, being characterized by a high hardness and a very good adherence to the substrate, while the flame coating presents oxides inclusions, high porosity, lower hardness and minimal dilution with the substrate as resulted from the EDS analyses. In depth characterization of the samples is made using optical and scanning electron microscopy, EDS analysis and microhardness testing.

Research about Relation between the Microstructures and Mechanical Properties of Metal Coating Layers

The paper presents the research about the correlation between the microstructures and mechanical properties of metal coating layers after laser heat treatment. The research was made with eight types of electrodes for welding coating. Laser heat treatment was applied after coating. Evaluation of results was made by observing the microstructures with metallographic microscopy, SEM/EDX and the mechanical properties were obtained by microhardness and wear resistance. The goal of this research is to study the influence of the laser heat treatment on wearing resistance of metal coating layers. Results reveal the influence of microstructures and chemical composition of used electrodes on microhardness and wear resistance of metal coating layers.

The Effect of Mo and Al on the Corrosion Behavior of Titanium and Some of its Alloys for Biomedical Applications

The influence of molybdenum and aluminum on the corrosion resistance of the Ti and other Ti-based biomedical implant alloys under simulated physiological conditions is presented. Ti and its alloys Ti-10Mo and Ti-10Mo-10Al were studied. The electrochemical impedance spectroscopy technique was used and the experimental results were compared with those obtained by potentiostatic and potentiodynamic techniques. All the measurements were made in Ringer ́s solution at different pH and at different potentials as Ecorr, -650, -500, 0, +200 and +400 mV vs SCE. It was evident that Mo improved passivity and limited the active corrosion of the β-phase of Ti while Al enrichment of the α-phase was found to be detrimental to the passivity and corrosion resistance of Ti. In most experimental conditions, the passive film is formed by TiO2, Ti2O3 and TiO. When pH is very low, thermodynamically stable state of Ti is titanium anion Ti3+.

Research about Wearing Resistance of Metal Coating Layers

The paper presents a research about influence of nitrocarburizing on wear resistance of metal coating layer. The research was made using six types of electrodes (El CrMn2, ElCrW8Co, El CrW2, E Cr25Ni20R, E 3161, El 62 H) for metal coating. After metal coating, were applied three variants of plasma nitrocarburizing, and was study their influence on wear resistance. Evaluation of results was made by weighing loss of samples after wearing.