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F T Cheng - One of the best experts on this subject based on the ideXlab platform.
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cavitation Erosion Resistance of aisi 316l stainless steel laser surface modified with niti
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: K Y Chiu, F T Cheng, Hau Chung ManAbstract:Abstract The present study is part of a project on the surface modification of AISI 316 stainless steel using various forms of NiTi for enhancing cavitation Erosion Resistance. In this study, NiTi powder was preplaced on the AISI 316L substrate and melted with a high-power CW Nd:YAG laser. With appropriate laser processing parameters, an alloyed layer of a few hundred micrometers thick was formed and fusion bonded to the substrate without the formation of a brittle interface. EDS analysis showed that the layer contained Fe as the major constituent element while the XRD patterns of the surface showed an austenitic structure, similar to that of 316 stainless steel. The cavitation Erosion Resistance of the modified layer (316-NiTi-Laser) could reach about 29 times that of AISI 316L stainless steel. The improvement could be attributed to a much higher surface hardness and elasticity as revealed by instrumented nanoindentation tests. Among various types of samples, the cavitation Erosion Resistance was ranked in descending order as: NiTi plate > 316-NiTi-Laser > 316-NiTi-TIG > AISI 316L, where 316-NiTi-TIG stands for samples surfaced with the tungsten inert gas (TIG) process using NiTi wire. Though the laser-surfaced samples and the TIG-surfaced samples had similar indentation properties, the former exhibited a higher Erosion Resistance mainly because of a more homogeneous alloyed layer with much less defects. In both the laser-surfaced and TIG-surfaced samples, the superelastic behavior typical of austenitic NiTi was only partially retained and the superior cavitation Erosion Resistance was thus still not fully attained.
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improvement in cavitation Erosion Resistance of a copper based propeller alloy by laser surface melting
Surface & Coatings Technology, 2004Co-Authors: C H Tang, F T ChengAbstract:Abstract Laser surface melting (LSM) of manganese–nickel–aluminium bronze (MAB), a common marine propeller alloy, was performed with the aim of improving the cavitation Erosion Resistance. Melting was achieved using a 2-kW continuous wave Nd:YAG laser with different scanning speeds and beam diameters, yielding different values of laser fluence. LSM resulted in a melt layer with a thickness of a few hundred micrometer thick, with the microhardness value at the surface increased to more than twice that of as-received MAB. The microstructure of the melt layer is highly refined and homogenized and has a single-phase b.c.c. structure (β phase), in contrast to the complex and heterogeneous microstructure of as-received MAB. With optimum laser parameters (power=1 kW; scanning velocity=35 mm/s; spot diameter=2 mm), the cavitation Erosion Resistance in 3.5 wt.% NaCl solution was improved by 5.8 and 2.2 times compared with that of as-received MAB and nickel–aluminium bronze (NAB), respectively. The improvement in cavitation Erosion Resistance is attributable to increased hardness and also to a much more homogeneous microstructure. Detailed analysis of the evolution of the morphology of the cavitated surface by SEM revealed totally different damage mechanisms for untreated and laser surface-melted MAB. For untreated MAB, the cavitation attack started at the κI phase, followed by an attack at the α/β phase boundary during the initial stage and eventually developed into ductile tearing of the matrix. However, the laser surface-melted samples only exhibited slight grain boundary attack at the initial stage, being initiating from triple junctions. In addition, the damaged surface of the laser-treated samples showed fracture of a more brittle nature.
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Laser transformation hardening of AISI 440C martensitic stainless steel for higher cavitation Erosion Resistance
Surface & Coatings Technology, 2003Co-Authors: Kin Ho Lo, F T ChengAbstract:Abstract Surface hardening of AISI 440C martensitic stainless steel was achieved by laser transformation hardening (LTH) using a high-power CW Nd:YAG laser. A hardened layer of a few 100 μm thick, composed of martensite, retained austenite and fine carbides was formed. The microstructure and hardness of the laser-treated layer were dependent on the laser processing parameters, with the hardness values reaching the range 600–800 HV. Compared with conventionally heat-treated samples, the laser-treated samples contained more retained austenite and finer carbides due to a higher degree of carbide dissolution. The cavitation Erosion Resistance of AISI 440C was significantly improved after laser treatment, and was approximately three-fold higher compared with that achieved by conventional heat treatment. The high Erosion Resistance was attributable to a desirable microstructure, which exhibited a favorable combination of hardness and toughness, and contained fewer weak sites for Erosion attack.
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Improvement of cavitation Erosion Resistance of AISI 316 stainless steel by laser surface alloying using fine WC powder
Surface & Coatings Technology, 2003Co-Authors: F T Cheng, Chi Tat Kwok, Hau Chung ManAbstract:Abstract Fine WC powder of approximately 1 μm size was employed as a convenient source of tungsten and carbon in the laser surface alloying of AISI 316 stainless steel for improving the cavitation Erosion Resistance. A slurry containing WC powder was preplaced on the substrate by pasting and processed with a high-power CW Nd:YAG laser to achieve surface alloying. The composition and microstructure of the alloyed layer and the phases formed were investigated by energy-dispersive X-ray spectroscopy, optical microscopy, scanning electron microscopy, and X-ray diffractometry, respectively. The cavitation Erosion behavior of the laser surface-alloyed samples in 3.5% NaCl solution was studied with a vibratory cavitation Erosion tester. The microhardness of the alloyed layer increases with the total W content in the layer. By employing proper processing parameters, an alloyed layer that is hard but not too brittle can be formed, with a cavitation Erosion Resistance that may reach more than 30 times that of the as-received 316. The improvement in cavitation Erosion Resistance may be attributed to the increase of W in solid solution and to the precipitation of dendritic carbides, both resulting from the dissociation of the fine WC powder during laser processing.
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correlation of cavitation Erosion Resistance with indentation derived properties for a niti alloy
Scripta Materialia, 2001Co-Authors: F T ChengAbstract:Abstract An empirical relationship is established between the cavitation Erosion Resistance R e of a Ni-rich NiTi alloy and the quantity W / δ u , where W is the work of indentation and δ u is the unrecoverable plastic deformation. This relationship also provides evidence that both pseudoelasticity and pseudoplasticity contribute to cavitation Erosion Resistance.
Hau Chung Man - One of the best experts on this subject based on the ideXlab platform.
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cavitation Erosion Resistance of aisi 316l stainless steel laser surface modified with niti
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: K Y Chiu, F T Cheng, Hau Chung ManAbstract:Abstract The present study is part of a project on the surface modification of AISI 316 stainless steel using various forms of NiTi for enhancing cavitation Erosion Resistance. In this study, NiTi powder was preplaced on the AISI 316L substrate and melted with a high-power CW Nd:YAG laser. With appropriate laser processing parameters, an alloyed layer of a few hundred micrometers thick was formed and fusion bonded to the substrate without the formation of a brittle interface. EDS analysis showed that the layer contained Fe as the major constituent element while the XRD patterns of the surface showed an austenitic structure, similar to that of 316 stainless steel. The cavitation Erosion Resistance of the modified layer (316-NiTi-Laser) could reach about 29 times that of AISI 316L stainless steel. The improvement could be attributed to a much higher surface hardness and elasticity as revealed by instrumented nanoindentation tests. Among various types of samples, the cavitation Erosion Resistance was ranked in descending order as: NiTi plate > 316-NiTi-Laser > 316-NiTi-TIG > AISI 316L, where 316-NiTi-TIG stands for samples surfaced with the tungsten inert gas (TIG) process using NiTi wire. Though the laser-surfaced samples and the TIG-surfaced samples had similar indentation properties, the former exhibited a higher Erosion Resistance mainly because of a more homogeneous alloyed layer with much less defects. In both the laser-surfaced and TIG-surfaced samples, the superelastic behavior typical of austenitic NiTi was only partially retained and the superior cavitation Erosion Resistance was thus still not fully attained.
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Improvement of cavitation Erosion Resistance of AISI 316 stainless steel by laser surface alloying using fine WC powder
Surface & Coatings Technology, 2003Co-Authors: F T Cheng, Chi Tat Kwok, Hau Chung ManAbstract:Abstract Fine WC powder of approximately 1 μm size was employed as a convenient source of tungsten and carbon in the laser surface alloying of AISI 316 stainless steel for improving the cavitation Erosion Resistance. A slurry containing WC powder was preplaced on the substrate by pasting and processed with a high-power CW Nd:YAG laser to achieve surface alloying. The composition and microstructure of the alloyed layer and the phases formed were investigated by energy-dispersive X-ray spectroscopy, optical microscopy, scanning electron microscopy, and X-ray diffractometry, respectively. The cavitation Erosion behavior of the laser surface-alloyed samples in 3.5% NaCl solution was studied with a vibratory cavitation Erosion tester. The microhardness of the alloyed layer increases with the total W content in the layer. By employing proper processing parameters, an alloyed layer that is hard but not too brittle can be formed, with a cavitation Erosion Resistance that may reach more than 30 times that of the as-received 316. The improvement in cavitation Erosion Resistance may be attributed to the increase of W in solid solution and to the precipitation of dendritic carbides, both resulting from the dissociation of the fine WC powder during laser processing.
Alejandro Toro - One of the best experts on this subject based on the ideXlab platform.
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cavitation and high velocity slurry Erosion Resistance of welded stellite 6 alloy
Tribology International, 2012Co-Authors: S. A. Romo, J F Santa, Jorge Enrique Celis Giraldo, Alejandro ToroAbstract:Abstract The cavitation and slurry Erosion Resistances of Stellite 6 coatings and 13-4 stainless steel were compared in laboratory. The Cavitation Resistance (CR) was measured according to ASTM G32 standard and the Slurry Erosion Resistance (SER) was tested in a high-velocity Erosion tester under several impact angles. The results showed that the coatings improved the CR 15 times when compared to bare stainless steel. The SER of the coatings was also higher for all the impingement angles tested, the highest Erosion rate being observed at 45°. The main wear mechanisms were micro-cracking (cavitation tests), and micro-cutting and micro-ploughing (slurry Erosion tests).
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Slurry and cavitation Erosion Resistance of thermal spray coatings
Wear, 2009Co-Authors: J F Santa, L. A. Espitia, S. A. Romo, J A Blanco, Alejandro ToroAbstract:The slurry and cavitation Erosion Resistance of six thermal spray coatings were studied in laboratory and compared to that of an uncoated martensitic stainless steel. Nickel, chromium oxide and tungsten carbide coatings were applied by oxy fuel powder (OFP) process and chromium and tungsten carbide coatings were obtained by high velocity oxy fuel (HVOF) process. The microstructure of the coatings was analyzed by light optical microscopy (LOM) and scanning electron microscopy (SEM), as well as by X-ray diffraction (XRD). The cavitation Erosion Resistance of the coatings was measured in a vibratory apparatus according to ASTM G32 standard and the slurry Erosion tests were carried out in a modified centrifugal pump in which the samples were conveniently placed to guarantee grazing incidence conditions, as well as in a high velocity jet Erosion testing machine. The results showed that the slurry Erosion Resistance of the steel can be improved up to 16 times by the application of the thermally sprayed coatings. On the other hand, none of the coated specimens showed better cavitation Resistance than the uncoated steel in the experiments. The main mass removal mechanisms observed in all the coatings submitted to slurry Erosion were micro-cutting and micro-ploughing as well as detachment of hard particles. In cavitation Erosion, OFP coatings showed brittle fracture and microcracking, and in nickel-based coatings some ductile deformation was also observed. In HVOF coatings, detachment of small particles led to coalescence of pores in WC/Co coatings while in CrC coatings the main wear mechanism was brittle fracture of particles.
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the effect of testing temperature on corrosion Erosion Resistance of martensitic stainless steels
Wear, 2003Co-Authors: Dairo Hernan Mesa, Alejandro Toro, Amilton Sinatora, Andre Paulo TschiptschinAbstract:Conventional AISI 420 and high-nitrogen martensitic stainless steels were tested under corrosion–Erosion conditions in slurry composed by substitute ocean water and quartz particles. The tests were performed at 0, 25, and 70 ◦ C, with mean impact angles of 20 and 90 ◦ . Polarization tests in H2SO4 solution containing chloride ions were also carried out at the same temperatures. Both conventional and high-nitrogen specimens were tempered at 200 and 450 ◦ C before the tests. The high-nitrogen specimens were produced through gas nitriding of AISI 410S (13%Cr–0.03%C) and AISI 410 (13%Cr–0.15%C) stainless steels at 1100 ◦ C. These treatments allowed obtaining interstitial contents (nitrogen + carbon) at the surface of the specimens equivalent to the carbon content of conventional AISI 420 stainless steel. The best corrosion–Erosion Resistance was obtained in the nitrided AISI 410S samples tempered at 200 ◦ C and tested at 0 ◦ C under 20 ◦ -impact angle. Increasing testing temperature led to higher mass losses and wear rates due to the intensification of intergranular and pitting corrosion mechanisms, especially in the conventional AISI 420 stainless steels. In tests performed at 0 and 25 ◦ C, a reduction in the wear rate for longer testing times was observed, which was mainly associated to fragmentation and roughness changes of the abrasive particles. The mass losses under normal impact conditions were systematically higher than under oblique incidence, and some evidences of mass removal by brittle fracture were found after SEM examination of the worn surfaces. © 2003 Elsevier Science B.V. All rights reserved.
Andre Paulo Tschiptschin - One of the best experts on this subject based on the ideXlab platform.
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cavitation Erosion Resistance of low temperature plasma nitrided martensitic stainless steel
Wear, 2013Co-Authors: L. A. Espitia, Luis Bernardo Varela, Carlos Eduardo Pinedo, Andre Paulo TschiptschinAbstract:Abstract The cavitation Erosion Resistance of non-nitrided and low plasma nitrided AISI 410 martensitic stainless steel was evaluated according to ASTM G32 standard. Plasma nitriding was carried out in a hot wall DC-pulsed plasma reactor at 400 °C in a mixture of 75% of nitrogen and 25% of hydrogen during 20 h. The ASTM A 743 grade CA6NM stainless steel was used for comparison purposes. The microstructure of the steels was characterized by optical and scanning electron microscopy, as well as by X-ray diffraction. Expanded martensite and iron nitrides were formed at the surface of the martensitic AISI 410 stainless steel. Curves of mass loss, Erosion rate and roughness parameters were plotted as a function of exposure time. The 25 μm thick nitride layer showed two distinct regions: a first 5 μm thick layer just beneath the surface containing precipitated e Fe 3 N nitrides and expanded martensite and the rest of the layer constituted solely by expanded martensite. Iron nitride precipitation drastically reduced the incubation period, allowing detachment of entire grains due to the impact of shock-waves over the surface. Despite this, after removal of the first 5 μm thick layer, the cavitation Erosion Resistance improved significantly. The relationship between microstructure and time-variation curves and wear mechanisms are discussed.
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improvement of the cavitation Erosion Resistance of an aisi 304l austenitic stainless steel by high temperature gas nitriding
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: Jose Francisco Fernandes Quirino Dos Santos, Carlos Mario Garzon, Andre Paulo TschiptschinAbstract:An AISI 304L austenitic stainless steel was high temperature gas nitrided in N2+Ar atmospheres under N2 partial pressures up to 0.10 MPa at 1423 K for 21.6 ks. Nitrogen contents at the surface up to 0.48 wt.% and case depths up to 1 mm were obtained. All the samples showed fully austenitic microstructures free of precipitates. Solution treated AISI 304L as well as nitrided samples were tested in distilled water in a vibratory cavitation Erosion (CE) equipment. Characterization of the test specimens was made by optical microscopy, electron back scattering diffraction coupled to a scanning electron microscope (EBSD–SEM), X-ray diffraction (XRD), wavelength dispersive spectroscopy (WDS) microanalysis and depth-sensing indentation tests. All the samples had almost the same mean grain diameter, ∼80m, similar mesotexture and microtexture, though the nitrogen contents differed. The nitrided samples exhibited much better cavitation Erosion Resistance and the Erosion rate was reduced by almost 8.5 times. Increasing the N2 partial pressure increased the nitrogen content at the surface, leading to an increase in the incubation period for damage and a decrease in the Erosion rate. © 2004 Elsevier B.V. All rights reserved.
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the effect of testing temperature on corrosion Erosion Resistance of martensitic stainless steels
Wear, 2003Co-Authors: Dairo Hernan Mesa, Alejandro Toro, Amilton Sinatora, Andre Paulo TschiptschinAbstract:Conventional AISI 420 and high-nitrogen martensitic stainless steels were tested under corrosion–Erosion conditions in slurry composed by substitute ocean water and quartz particles. The tests were performed at 0, 25, and 70 ◦ C, with mean impact angles of 20 and 90 ◦ . Polarization tests in H2SO4 solution containing chloride ions were also carried out at the same temperatures. Both conventional and high-nitrogen specimens were tempered at 200 and 450 ◦ C before the tests. The high-nitrogen specimens were produced through gas nitriding of AISI 410S (13%Cr–0.03%C) and AISI 410 (13%Cr–0.15%C) stainless steels at 1100 ◦ C. These treatments allowed obtaining interstitial contents (nitrogen + carbon) at the surface of the specimens equivalent to the carbon content of conventional AISI 420 stainless steel. The best corrosion–Erosion Resistance was obtained in the nitrided AISI 410S samples tempered at 200 ◦ C and tested at 0 ◦ C under 20 ◦ -impact angle. Increasing testing temperature led to higher mass losses and wear rates due to the intensification of intergranular and pitting corrosion mechanisms, especially in the conventional AISI 420 stainless steels. In tests performed at 0 and 25 ◦ C, a reduction in the wear rate for longer testing times was observed, which was mainly associated to fragmentation and roughness changes of the abrasive particles. The mass losses under normal impact conditions were systematically higher than under oblique incidence, and some evidences of mass removal by brittle fracture were found after SEM examination of the worn surfaces. © 2003 Elsevier Science B.V. All rights reserved.
Shuyun Jiang - One of the best experts on this subject based on the ideXlab platform.
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cavitation Erosion Resistance of diamond like carbon coating on stainless steel
Applied Surface Science, 2014Co-Authors: Feng Cheng, Shuyun JiangAbstract:Abstract Two diamond-like carbon (DLC) coatings are prepared on stainless steel 304 by cathodic arc plasma deposition technology at different substrate bias voltages and arc currents (−200 V/80 A, labeled DLC-1, and −100 V/60 A, labeled DLC-2). Cavitation tests are performed by using a rotating-disk test rig to explore the cavitation Erosion Resistance of the DLC coating. The mass losses, surface morphologies, chemical compositions and the phase constituents of the specimens after cavitation tests are examined by using digital balance, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The results indicate that the DLC-2 coatings can elongate the incubation period of stainless steel, leading to an excellent cavitation Erosion Resistance as compared to the untreated stainless steel specimens. After duration of 100 h cavitation test, serious damaged surfaces and plenty of scratches can be observed on the surfaces of the stainless steel specimens, while only a few grooves and tiny pits are observed on the DLC-2 coatings. It is concluded that, decreasing micro defects and increasing adhesion can reduce the delamination of DLC coating, and the Erosion continues in the stainless steel substrate after DLC coating failure, and the eroded surface of the substrate is subjected to the combined action from cavitation Erosion and slurry Erosion.
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cavitation Erosion Resistance of microarc oxidation coating on aluminium alloy
Applied Surface Science, 2013Co-Authors: Feng Cheng, Shuyun Jiang, Jun LiangAbstract:Abstract Two ceramic coatings are prepared on 2124 aluminum alloy by microarc oxidation (MAO) technology. To explore the cavitation Erosion Resistance of the MAO coating, cavitation tests were performed by using a rotating-disk test rig. The mass losses, surface morphologies, chemical compositions and the phase constituents of the samples after cavitation tests were examined by using digital balance, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The results indicate that the MAO coatings can extend the incubation period of aluminum alloy, and thus enhance the cavitation Erosion Resistance as compared to the untreated aluminum alloy samples. After duration of 63 h cavitation test, a lot of Erosion pits and the particles in various shapes can be observed on the surfaces of the aluminum alloy samples, while only a few Erosion pits are observed on the MAO coatings. Moreover, the mean depths of Erosion on the MAO coatings are lower in the first 30 h and are independent on Erosion time. The results show that the cavitation Erosion of MAO coating is governed by water mechanical impaction, resulting from the effects of brittle fracture of the MAO coating.
