Papers by Keyword: Laser Surface Alloying

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Authors: Enikő Bitay
Abstract: The present work aims to analyze the dispersion process (path) of the solid particles by moving a spherical particle from the feeding-nozzle outlet till the penetration of the melted surface (by the laser beam) and then its path in the metal bath. In laser surface treatment technologies with injection of hard particles in the melting bath it is necessary for the particles to work against the surface stress to penetrate through the surface of the bath into the melt. The theory shown was used in precalculations for the experiments carried out dispersing carbide particles (WC, TaC, NbC). Powder of particles of all three types were dispersed by means of the Ar carrying gas into an C15 steel melt by CO2 laser. Evaluating the results of this process taking into consideration different specific technological parameters (speed of the beam, powder feeding speed) one can conclude that all three carbide types can penetrate into the melt.
Authors: A.K. Pattanaik, A.S. Khanna, A. Gasser, C.S. Harendranath
Authors: Olga Turcan, Daniel Constantin Comeagă, Octavian Donţu, Ionelia Voiculescu
Abstract: Local surface alloying of metallic materials by laser is an issue of interest in the scientific world and materials engineering. Laser surface alloying technology allows diffusion of alloying elements which add special features into the surface of a base material with modest properties but a low price. This paper presents the results of experimental research regarding the process of alloying on steel ST37-2 and the effects obtained after laser surface alloying.
Authors: Damian Janicki
Abstract: Metal matrix composite layers were fabricated on AISI 304L substrate by diode laser surface alloying with direct injection of chromium carbide Cr3C2 powder into the molten-pool. The influence of laser alloying parameters on the quality of the alloyed layers were investigated. The alloyed layers were examined by optical metallography and scanning electron microscopy. Comparative erosion tests between the AISI 304L substrate and the alloyed layers have been performed following the ASTM G 76 standard test method. The uniform laser beam intensity profile of the laser used ensures to produce fully dense alloying layers with homogenous distribution of Cr3C2 particle throughout the matrix alloy. Distribution and dissolution of Cr3C2 particles are strongly dependent on the laser power level. The alloyed layers exhited noticeable increased erosion resistance in comparison to AISI 304L substrate for both 30° and 90° impact angles.
Authors: G. Rapheal, Subodh Kumar, Carsten Blawert, Narendra B. Dahotre
Abstract: A permanent mould cast creep resistant MRI 230D Mg alloy was laser surface alloyed (LSA) with Al and Al2O3 in order to improve its wear and corrosion resistance. However, this treatment was successful only in improving wear resistance but not corrosion resistance due to the presence of micro−cracks in the coated layer, which has been discussed in an earlier paper. The LSA coated Mg alloy has been further subjected to plasma electrolytic oxidation (PEO) treatment in alkaline silicate electrolyte in order to cover those micro−cracks and improve corrosion resistance, which is discussed in the present manuscript. For comparison, the PEO coating has also been applied on the as−cast MRI 230D Mg alloy. The microstructural characterization of coatings and corroded surfaces was carried out by scanning electron microscope and X−ray diffraction. Electrochemical corrosion tests were conducted in 3.5 wt% NaCl solution having neutral pH to investigate the corrosion behavior. The LSA coatings consisted mainly of β (Mg17Al12) phase, the coatings produced by PEO treatment on MRI 230D Mg alloy consisted mainly of Mg2SiO4 phase, and hybrid coatings of PEO on LSA consisted of Mg2SiO4 and MgAl2O4 phases in the PEO layer. Scanning electron micrographs of the cross−section revealed that the PEO treatment covered the micro−cracks present in the LSA and corrosion tests revealed that it improved the corrosion resistance, though not to the extent of the corrosion resistance of the PEO coated MRI 230D Mg alloy. All the samples exhibited localized form of corrosion.
Authors: Enikő Bitay, András Roósz
Abstract: The laser surface-treatment methods have been quickly developed by appearing of lasers with high power beam and can increase the hardness, of the surface. A very hard, wear-resisting layer can be produced by the dispersing of ceramic grains. The essence of the technology is, that such a material (compound-phase, e.g.: metal-oxide, carbide, nitride, etc.) is added to the surface layer melted by laser, which does not solve or solves only partly in the metal-melt. This work studies the effect of the different technological parameter (such as, power of the laserbeam, motion speed, amount of the ceramic particles etc.) on the different microstructure accrued during the laser surface alloying. The desired microstructure has homogeneous carbide distribution in the matrix. But it is embarrassed by several conditions. The aim of this present work is to find out the reasons for the inhomogeneous ceramic particle distribution inside the matrix and to discover these embarrassing conditions.
Authors: Wen Yan Wang, Xiao Ming Dong, Jing Pei Xie
Abstract: A ductile iron coated with metal-matrix pastes containing hard phase TiC and CrxCy was laser alloyed by an Nd: YAG laser and a CO2 laser. The microstructure, composition and wear resistance were analyzed by scanning electron microscopy (SEM), incorporating energy dispersive spectrum (EDS), X-ray diffraction analysis (XRD) and friction wear tester respectively. Results revealed that the alloyed area was composed by alloyed zone and heat affected zone. The microstructure of the alloyed layer was significantly influenced by the laser beam kind. Finer grains and fewer cementites were contained in the alloyed layer produced by Nd: YAG laser. Friction and wear experiments showed that the alloyed layer had better tribology properties.
Authors: Gui Fang Sun, Chang Sheng Liu, Jing Liang, Jun Hua Zhou, Xing Qi Tao
Abstract: The laser surface alloying(LSA) technique was firstly used to form wear resistant layers on nodular cast iron rolls with two different powders, A: NiCr-Cr3C2 and B: C-B-W-Cr. The microstructure, element distribution and phases of the layers were investigated. Results indicate that the alloying layers had pores and cracks, as well as a metallurgical bonding with the substrates. For layers with powder A, as the thickness of the pre-layers decreased, the numbers of pores and cracks of the LSA layers decreased but the thicknesses of them were close. Phases were barely influenced by the thickness of the pre-layer, while the content of them were affected. For layers with powder B, as the laser specific energy increased, the numbers of pores and cracks in the LSA layers decreased and the thicknesses of them increased. The microstructure in the layers with different powders was different.
Authors: Gyula Králik, Piroska Fülöp, Balázs Verő, Dénes Zsámbók
Authors: Qing Yu, Yao Ning Sun, Wen Lei Sun, Xu Dong Zhang
Abstract: Using laser cladding technique, TiC reinforced Ti matrix composite coatings were fabricated by preplacing TiC, (Ti+C), (Ti+TiC) powders respectively on the TA2 pure titanium surface.By means of XRD, SEM and Hv-Test, microstructures and microhardness were investigated. The results show that phases of the coatings are all composed of TiC and α-Ti. Delamination phenomenon appears when laser clad pure TiC coating, which has deleterious effect on properties. TiC phase is in-situ synthesized during laser clad (Ti+C) coating, but microstructure is coarse. Microstructure of (Ti+TiC) coating is the most uniform and dense of the three coatings. The microhardness sequence of the three coatings is (Ti+TiC)>TiC>(Ti+C), and the maximum value is Hv1246, Hv1213 and Hv1135 respectively. The main reason leads to the highest micro-hardness of (Ti+TiC) coating is the Ti powder is beneficial to laser cladding and large amount of TiC reinforcement formed which is compact and uniform.
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