Jari Tuominen
Tampere University, Materials Science, Post-Doc
The general specification of nickel-base alloy 625 is quite permissible allowing relatively large variations in chemical composition. In directed energy deposition processes including laser cladding and additive manufacturing, the powder... more
The general specification of nickel-base alloy 625 is quite permissible allowing relatively large variations in chemical composition. In directed energy deposition processes including laser cladding and additive manufacturing, the powder plays a key role in the properties of final products. Therefore, it is important to select the highest-quality powder. Several commercially available alloy 625 powders were characterized and deposited on mild steel by the laser cladding process using a coaxial powder feeding method and a single bead. Clad layer characterization consisted of determination of dilution and quantification of hot cracks. The results showed that powders containing the lowest amount of impurity elements (S, P, B) were the most resistant to hot cracking. Ti and Al were beneficial if impurity element contents were high.
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In the last few years, coaxial laser heads have been developed with centric wire feeding equipment, which enables the laser processing of complex-shaped objects in various applications. These newly developed laser heads are being used... more
In the last few years, coaxial laser heads have been developed with centric wire feeding equipment, which enables the laser processing of complex-shaped objects in various applications. These newly developed laser heads are being used particularly in laser brazing experiments in the automotive industry. This study presents experimental results of using a coaxial laser head for cold- and hot-wire cladding application. The coaxial wire cladding method has significant improvements compared with the off-axis wire cladding method such as independence of the travel direction, alignment of the wire to the laser beam, and a reduced number of controlling parameters. These features are important to achieve high quality coatings. Cladding tests were conducted on mild steel with a coaxial laser wire welding head using Ni-based Inconel 625 and Thermanit 2509 super duplex stainless steel solid wires in order to determine the properties of the cladding process and the coatings deposited. The corro...
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In the present study, surface engineering related to simultaneously thermally sprayed and laser melted corrosion resistant coatings has been carried out. A 6 kW high power diode laser or a Nd:YAG laser and a flame spray gun were used to... more
In the present study, surface engineering related to simultaneously thermally sprayed and laser melted corrosion resistant coatings has been carried out. A 6 kW high power diode laser or a Nd:YAG laser and a flame spray gun were used to construct the laser assisted thermal spraying system. The main aims of the study were to find out the optimal processing parameters and materials to create dense corrosion resistant coatings on steels. The corrosion resistance of the manufactured coatings was measured and the microstructure characterized using optical and scanning electron microscopy.
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Laser cladding is a surface treatment technology in which thick, dense and metallurgically adhered metallic layers are deposited on various structural steels with relatively low heat input, high accuracy and reproducibility. Laser... more
Laser cladding is a surface treatment technology in which thick, dense and metallurgically adhered metallic layers are deposited on various structural steels with relatively low heat input, high accuracy and reproducibility. Laser cladding processes used in industrial cladding are largely based on the use of CO2 or Nd:YAG lasers. High power diode lasers (HPDL) with rectangular beam spots are regarded as ideal laser sources for laser cladding processes, due to their compact size, high electrical to optical efficiency, easy operation, and low investment and running costs. In laser cladding of large surface areas, the affectivity of the laser cladding process becomes more important, i.e. high laser powers, wide laser beam spots, and high coating material feedrates are regarded as beneficial. In order to optimise the cladding process for such applications, special attention has to be put on devices used to deliver the coating power to the process. In the present work, various parameters...
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Thermal spray processes are widely used to deposit high-chromium nickel-chromium coatings to improve high temperature oxidation and corrosion behaviour. However, in spite of the efforts made to improve the present spraying techniques,... more
Thermal spray processes are widely used to deposit high-chromium nickel-chromium coatings to improve high temperature oxidation and corrosion behaviour. However, in spite of the efforts made to improve the present spraying techniques, such as HVOF and plasma spraying, these coatings may still exhibit certain defects such as unmelted particles, oxide layers at splat boundaries, porosity and cracks, which are detrimental to corrosion performance in severe operation conditions. Due to low process temperature only mechanical bonding is obtained between the coating and substrate. Laser remelting of the sprayed coatings was studied in order to overcome the drawbacks of sprayed structures and to markedly improve the coating properties. The coating material was high-chromium nickel-chromium alloy, which contains small amounts of molybdenum and boron (53.3%Cr- 42.5%Ni - 2.5%Mo - 0.5%B). The coatings were prepared by high-velocity oxy-fuel spraying onto mild steel substrates. High power fiber...
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Fusion-bonded and low-diluted overlay welded coatings are frequently very thick (>1mm). High-speed laser cladding is a novel process capable of producing thin fusion-bonded and low-diluted coatings with high coverage rates and low heat... more
Fusion-bonded and low-diluted overlay welded coatings are frequently very thick (>1mm). High-speed laser cladding is a novel process capable of producing thin fusion-bonded and low-diluted coatings with high coverage rates and low heat input. In this study, for the first time, high-speed laser cladding was used to fabricate relatively thin Ni-based coatings reinforced with chromium carbides onto low-alloy structural and quenched and tempered steels. Obtained coatings were characterized with X-ray diffraction (XRD), optical (OM), and scanning electron microscopy (SEM), as well as electron backscatter diffraction (EBSD). Mechanical and wear properties were tested with Vickers microhardness measurements and three-body dry-sand rubber wheel abrasion tests (RWAT). It was shown that high-speed laser cladding produces 0.2–0.3-mm-thick coatings, which consist of ultrafine-substructured hypereutectic M7C3 structures reinforced with coarser primary Cr3C2 particles. Coatings with hardness u...
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High power diode lasers (HPDL) at the level of ? 6 kW are efficient cladding tools in heavy engineering applications where thick (up to 5 mm) wear and corrosion resistant coating layers are required. Large beam geometry makes possible the... more
High power diode lasers (HPDL) at the level of ? 6 kW are efficient cladding tools in heavy engineering applications where thick (up to 5 mm) wear and corrosion resistant coating layers are required. Large beam geometry makes possible the overlap of thick 20 mm wide cladding tracks side by side without coating defects. Compact size and closed cooling water circulation enable HPDL cladding process to take place also at a site of new or worn high-value machine parts, which have worn in operation or been damaged already during overseas transportation. Instead of moving parts of several tons’ weight, it would be perhaps more cost efficient to transport HPDL cladding unit.
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In High-North mining, oil & gas, offshore and metal industries face large challenges in wear, corrosion, fatigue and excessive energy consumption. To address these needs, novel cost-effcient and environmentally friendly surfacing and... more
In High-North mining, oil & gas, offshore and metal industries face large challenges in wear, corrosion, fatigue and excessive energy consumption. To address these needs, novel cost-effcient and environmentally friendly surfacing and additive manufacturing technologies based on cold-arc and laser hybrid metal deposition techniques are developed. Development, adoption and commercialisation of high productivity deposition techniques enable: 1) Fabrication of low diluted and fusion bonded coatings with enhanced wear and corrosion properties with low friction and anti-icing properties, 2) Fabrication of large near net-shape 3D metal objects with 30-40% more weight efficient structures compared with conventional manufacturing techniques.publishedVersionNon peer reviewe
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Cold metal transfer (CMT) welding technique was used in the manufacturing of hypoeutectic carbide-type Co-based Stellite 12 hardfacings on martensitic stainless steel. It was discovered that the CMT process is capable of producing... more
Cold metal transfer (CMT) welding technique was used in the manufacturing of hypoeutectic carbide-type Co-based Stellite 12 hardfacings on martensitic stainless steel. It was discovered that the CMT process is capable of producing relatively thick (> 2.5 mm) low diluted single-layer coatings with cored Stellite 12 wire without cracks and pores. These coatings were investigated using microscopy (optical and scanning electron microscopy), X-ray diffraction, and hardness measurements. The high melting point chromium and tungsten particles inside the cored wire were relatively large and therefore remained unmelted in the clad layers. Self-mated sliding wear tests were performed using a pin-on-disc tribometer at room temperature and at 300 °C to determine the wear resistance and friction of the coatings. The coefficients of friction were relatively similar (~ 0.35) at both temperatures. Differences were exhibited in the ~ 40% greater loss of material at high temperature. The wear per...
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Applying laser cladded components in expensive machines and engines requires knowledge of residual stresses in order to avoid unexpected failures and further damages. Normally residual stresses induced by laser cladding are highly tensile... more
Applying laser cladded components in expensive machines and engines requires knowledge of residual stresses in order to avoid unexpected failures and further damages. Normally residual stresses induced by laser cladding are highly tensile due to strong thermal gradients. This makes laser coatings susceptible to fatigue and stress corrosion cracking for instance. Laser-induced residual stress state depends on several material and processing parameters. Some of them, for example the effect of subsequent hardening treatment on residual stresses of Stellite 21 coatings on martensitic stainless steel with and without intermediate layers and the effect of heat input were studied here. The residual stresses were measured using X-ray diffraction method.Applying laser cladded components in expensive machines and engines requires knowledge of residual stresses in order to avoid unexpected failures and further damages. Normally residual stresses induced by laser cladding are highly tensile due to strong thermal gradients. This makes laser coatings susceptible to fatigue and stress corrosion cracking for instance. Laser-induced residual stress state depends on several material and processing parameters. Some of them, for example the effect of subsequent hardening treatment on residual stresses of Stellite 21 coatings on martensitic stainless steel with and without intermediate layers and the effect of heat input were studied here. The residual stresses were measured using X-ray diffraction method.
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Laser cladding is overlay welding method to manufacture high performance, fusion bonded metal and metal matrix composite (MMC) coatings on metallic substrates with low dilution. Owing to steep thermal gradients, rapid solidification and... more
Laser cladding is overlay welding method to manufacture high performance, fusion bonded metal and metal matrix composite (MMC) coatings on metallic substrates with low dilution. Owing to steep thermal gradients, rapid solidification and possible mismatch in coefficients of thermal expansion (CTE) between coating and substrate, laser cladding induces large tensile residual stresses in coating layer, potentially affecting the service life of clad component under external load-induced stresses. In this study, 4-point bending and torsion fatigue tests were conducted on relatively large round laser clad steel bars to determine the effect of laser cladding on fatigue strength. Quenched and tempered (QT) 42CrMo4 steel clad with Inconel 625 and S355 structural steel clad with Stellite 21 were subjected to various stress levels for relatively large number of cycles with and without post weld heat treatment (PWHT). The results showed that Stellite 21 decreased the fatigue life of S355 at all the applied loads whereas Inconel 625 increased the fatigue life of 42CrMo4 at high loads but decreased at low loads. Applied PWHT did not show any positive influence on fatigue life.Laser cladding is overlay welding method to manufacture high performance, fusion bonded metal and metal matrix composite (MMC) coatings on metallic substrates with low dilution. Owing to steep thermal gradients, rapid solidification and possible mismatch in coefficients of thermal expansion (CTE) between coating and substrate, laser cladding induces large tensile residual stresses in coating layer, potentially affecting the service life of clad component under external load-induced stresses. In this study, 4-point bending and torsion fatigue tests were conducted on relatively large round laser clad steel bars to determine the effect of laser cladding on fatigue strength. Quenched and tempered (QT) 42CrMo4 steel clad with Inconel 625 and S355 structural steel clad with Stellite 21 were subjected to various stress levels for relatively large number of cycles with and without post weld heat treatment (PWHT). The results showed that Stellite 21 decreased the fatigue life of S355 at all the applied loads where...
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A series of experiments were performed to investigate the one-step laser cladding of Inconel 625 powder, injected off-axially on mild steel substrates. The experiments were carried out using a 6 kW high power diode laser (HPDL) mounted to... more
A series of experiments were performed to investigate the one-step laser cladding of Inconel 625 powder, injected off-axially on mild steel substrates. The experiments were carried out using a 6 kW high power diode laser (HPDL) mounted to 6 axis robot system. The rectangular shape of the delivering beam was focused to a spot size of 22 mm x 5 mm on the work piece. The powder feeding head, which consisted of cyclone and flat nozzle, spread the powder stream to a spot size used. The coating samples were produced using different levels of powder feed rate (77 – 113 g/min), constant travelling speed of 400 mm/min and laser power of 6 kW.The corrosion resistance of the one-step laser-clad coatings were tested in 3.5 wt. % NaCl using electrochemical methods. Laser-clad coating was compared with wrought Inconel 625 alloy, high-velocity oxy-fuel (HVOF) sprayed and plasma transferred arc (PTA) welded coatings. The corrosion resistance of laser-clad coatings was found to be equivalent to corresponding bulk material and superior to sprayed and welded coatings.A series of experiments were performed to investigate the one-step laser cladding of Inconel 625 powder, injected off-axially on mild steel substrates. The experiments were carried out using a 6 kW high power diode laser (HPDL) mounted to 6 axis robot system. The rectangular shape of the delivering beam was focused to a spot size of 22 mm x 5 mm on the work piece. The powder feeding head, which consisted of cyclone and flat nozzle, spread the powder stream to a spot size used. The coating samples were produced using different levels of powder feed rate (77 – 113 g/min), constant travelling speed of 400 mm/min and laser power of 6 kW.The corrosion resistance of the one-step laser-clad coatings were tested in 3.5 wt. % NaCl using electrochemical methods. Laser-clad coating was compared with wrought Inconel 625 alloy, high-velocity oxy-fuel (HVOF) sprayed and plasma transferred arc (PTA) welded coatings. The corrosion resistance of laser-clad coatings was found to be equivalent to corresponding bulk material...
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Some properties of laser claddings made with several commercially available alloy 625 powders were investigated. Nickel based alloy 625, generally known also as Inconel 625, is widely used also on laser claddings due to its good corrosion... more
Some properties of laser claddings made with several commercially available alloy 625 powders were investigated. Nickel based alloy 625, generally known also as Inconel 625, is widely used also on laser claddings due to its good corrosion properties in various environments. The general specification of alloy 625 is quite permissible and it has been discovered that there can be relatively large variation on properties of alloy 625 powders depending on powder manufacturer and powder batches. And these variations on powder lead to variations on properties of subsequent cladding. The emphasis on this study is especially on the variation of the tendency to hot cracking on laser cladding.Some properties of laser claddings made with several commercially available alloy 625 powders were investigated. Nickel based alloy 625, generally known also as Inconel 625, is widely used also on laser claddings due to its good corrosion properties in various environments. The general specification of alloy 625 is quite permissible and it has been discovered that there can be relatively large variation on properties of alloy 625 powders depending on powder manufacturer and powder batches. And these variations on powder lead to variations on properties of subsequent cladding. The emphasis on this study is especially on the variation of the tendency to hot cracking on laser cladding.
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In the present study, surface engineering research related to thermally sprayed Ni-based corrosion resistant coatings modified by in-situ and post treatment by novel high power lasers (Nd:YAG and diode lasers) has been carried out. The... more
In the present study, surface engineering research related to thermally sprayed Ni-based corrosion resistant coatings modified by in-situ and post treatment by novel high power lasers (Nd:YAG and diode lasers) has been carried out. The main aim of the study was to create experimental based information and knowledge on simultaneous remelting of thermally sprayed (plasma, HVOF, flame) layers for production of metallurgically bonded, dense corrosion resistant coatings on surfaces of steels and cast irons. The two main focuses of research were to evaluate the needed processing parameters, which enable simultaneous laser assisted thermal spraying and to investigate the corrosion resistance of the obtained coatings in comparison with laser remelted and thermally sprayed coatings.
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ABSTRACT The results of experimental studies of the process of laser cladding with scanning with the help of a 15-kW fiber laser are presented. The surface layers are deposited in the form of single tracks and continuous coatings. The... more
ABSTRACT The results of experimental studies of the process of laser cladding with scanning with the help of a 15-kW fiber laser are presented. The surface layers are deposited in the form of single tracks and continuous coatings. The substrate material is low-carbon steel. The advantages of the use of high-power lasers for laser cladding are demonstrated.
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... Coating-phase structures were char-acterized by image plate x-ray diffraction (XRD; Italstructures, Riva del Garda, Italy) using filtered CuK radiation, with the diffractometer operating at 40 ... R.Sivakumar and BL Mordike: Laser... more
... Coating-phase structures were char-acterized by image plate x-ray diffraction (XRD; Italstructures, Riva del Garda, Italy) using filtered CuK radiation, with the diffractometer operating at 40 ... R.Sivakumar and BL Mordike: Laser Melting of Plasma Sprayed Ceramic Coatings, Surf ...
Research Interests: Materials Engineering, Mechanical Engineering, Materials Science, Scanning Electron Microscopy, Transmission Electron Microscopy, and 15 moreGAS TURBINE, Coating, Optical microscopy, Composite Material, Thermal, Thermal Spray Technology, Diesel engine, X ray diffraction, Microstructures, Elastic Modulus, Thermal Barrier Coating, Energy Dispersive Spectroscopy, Plasma Spraying, Corrosion Resistance, and Mechanical Property
Thermal spray processes are widely used to protect materials and components against wear, corrosion and oxidation. Despite the use of the latest developments of thermal spraying, such as high-velocity oxy-fuel (HVOF) and plasma spraying,... more
Thermal spray processes are widely used to protect materials and components against wear, corrosion and oxidation. Despite the use of the latest developments of thermal spraying, such as high-velocity oxy-fuel (HVOF) and plasma spraying, these coatings may in certain service conditions show inadequate performance,e.g., due to insufficient bond strength and/or mechanical properties and corrosion resistance inferior to those of corresponding
Research Interests: Materials Engineering, Mechanical Engineering, Materials Science, Scanning Electron Microscopy, Corrosion, and 13 moreOptical microscopy, Chromium, High Temperature, Nickel, Thermal Spray Technology, Bond Strength, High Power, Thermal spray, Mild Steel, Plasma Spraying, Corrosion Resistance, Continuous Wave, and Mechanical Property
Thermal spray processes are widely used to deposit high-chromium, nickel-chromium coatings to improve high temperature oxidation and corrosion behavior. However, despite the efforts made to improve the present spraying techniques, such as... more
Thermal spray processes are widely used to deposit high-chromium, nickel-chromium coatings to improve high temperature oxidation and corrosion behavior. However, despite the efforts made to improve the present spraying techniques, such as high-velocity oxyfuel (HVOF) and plasma spraying, these coatings may still exhibit certain defects, such as unmelted particles, oxide layers at splat boundaries, porosity, and cracks, which are detrimental to corrosion performance in severe operating conditions. Because of the process temperature, only mechanical bonding is obtained between the coating and substrate. Laser remelting of the sprayed coatings was studied in order to overcome the drawbacks of sprayed structures and to markedly improve the coating properties. The coating material was high-chromium, nickel-chromium alloy, which contains small amounts of molybdenum and boron (53.3% Cr, 42.5% Ni, 2.5% Mo, 0.5% B). The coatings were prepared by HVOF spraying onto mild steel substrates. A high-power, fiber-coupled, continuous-wave Nd:YAG laser equipped with large beam optics was used to remelt the HVOF-sprayed coating using different levels of scanning speed and beam width (10 or 20 mm). Coating that was remelted with the highest traverse speed suffered from cracking because of the rapid solidification inherent to laser processing. However, after the appropriate laser parameters were chosen, nonporous, crack-free coatings with minimal dilution between coating and substrate were produced. Laser remelting resulted in the formation of a dense oxide layer on top of the coatings and full homogenization of the sprayed structure. The coatings as sprayed and after laser remelting were characterized by optical and electron microscopy (OM, SEM, respectively). Dilution between coating and substrate was studied with energy dispersive spectrometry (EDS). The properties of the laser-remelted coatings were directly compared with properties of as-sprayed HVOF coatings.
Research Interests: Materials Engineering, Mechanical Engineering, Materials Science, Electron Microscopy, Corrosion, and 14 moreChromium, High Temperature, Nickel, Thermal Spray Technology, High Power, Laser processing, Operant Conditioning, Thermal spray, Mild Steel, Rapid solidification, Plasma Spraying, Continuous Wave, Energy Dispersive Spectrometry, and Hvof
Thermal spray processes are widely used to deposit high-chromium, nickel-chromium coatings to improve high temperature oxidation and corrosion behavior. However, despite the efforts made to improve the present spraying techniques, such as... more
Thermal spray processes are widely used to deposit high-chromium, nickel-chromium coatings to improve high temperature oxidation and corrosion behavior. However, despite the efforts made to improve the present spraying techniques, such as high-velocity oxyfuel (HVOF) and plasma spraying, these coatings may still exhibit certain defects, such as unmelted particles, oxide layers at splat boundaries, porosity, and cracks, which are detrimental to corrosion performance in severe operating conditions. Because of the process temperature, only mechanical bonding is obtained between the coating and substrate. Laser remelting of the sprayed coatings was studied in order to overcome the drawbacks of sprayed structures and to markedly improve the coating properties. The coating material was high-chromium, nickel-chromium alloy, which contains small amounts of molybdenum and boron (53.3% Cr, 42.5% Ni, 2.5% Mo, 0.5% B). The coatings were prepared by HVOF spraying onto mild steel substrates. A high-power, fiber-coupled, continuous-wave Nd:YAG laser equipped with large beam optics was used to remelt the HVOF-sprayed coating using different levels of scanning speed and beam width (10 or 20 mm). Coating that was remelted with the highest traverse speed suffered from cracking because of the rapid solidification inherent to laser processing. However, after the appropriate laser parameters were chosen, nonporous, crack-free coatings with minimal dilution between coating and substrate were produced. Laser remelting resulted in the formation of a dense oxide layer on top of the coatings and full homogenization of the sprayed structure. The coatings as sprayed and after laser remelting were characterized by optical and electron microscopy (OM, SEM, respectively). Dilution between coating and substrate was studied with energy dispersive spectrometry (EDS). The properties of the laser-remelted coatings were directly compared with properties of as-sprayed HVOF coatings.
Research Interests: Materials Engineering, Mechanical Engineering, Materials Science, Electron Microscopy, Corrosion, and 14 moreChromium, High Temperature, Nickel, Thermal Spray Technology, High Power, Laser processing, Operant Conditioning, Thermal spray, Mild Steel, Rapid solidification, Plasma Spraying, Continuous Wave, Energy Dispersive Spectrometry, and Hvof
Zirconia-based 8Y2O3-ZrO2 and 22MgO-ZrO2 thick thermal barrier coatings (TTBC, 1000 µm), were studied with different sealing methods for diesel engine applications. The aim of the sealing procedure was to improve hot corrosion resistance... more
Zirconia-based 8Y2O3-ZrO2 and 22MgO-ZrO2 thick thermal barrier coatings (TTBC, 1000 µm), were studied with different sealing methods for diesel engine applications. The aim of the sealing procedure was to improve hot corrosion resistance and mechanical properties of porous TBC coatings. The surface of TTBCs was sealed with three different methods: (1) impregnation with phosphate-based sealant, (2) surface melting by laser
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ABSTRACT A series of experiments were performed to investigate the one-step laser cladding of Inconel 625 powder, injected off-axially onto mild steel substrates. The experiments were carried out using a 6 kW high power diode laser... more
ABSTRACT A series of experiments were performed to investigate the one-step laser cladding of Inconel 625 powder, injected off-axially onto mild steel substrates. The experiments were carried out using a 6 kW high power diode laser mounted to a six axis robot system. The rectangular shape of the delivering beam was focused to a spot size of 22 mm×5 mm on the work piece. The powder feeding head, which consisted of a cyclone and flat nozzle, spread the powder stream to a spot size used. The coating samples were produced using different levels of powder feed rate (77–113 g/min), constant traveling speed of 400 mm/min, and laser power of 6 kW. Powder and laser-clad coating microstructures were studied by x-ray diffraction, scanning electron, and optical microscopy. The coating microstructure was found to consist of a directionally solidified single phase (highly alloyed Ni), face-centered cubic structure with a lattice parameter of 0.3596 nm. The corrosion resistance of the one-step laser-clad coatings was tested in 3.5 wt % NaCl using electrochemical methods. Laser-clad coating was compared with wrought Inconel 625 alloy, high-velocity oxy-fuel sprayed, and plasma transferred arc welded coatings. The corrosion resistance of laser-clad coatings was found to be equivalent to corresponding bulk material and superior to sprayed and welded coatings.
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In the present study, surface engineering research related to thermally sprayed wear and corrosion resistant coatings modified by in-situ and post-treatment by novel high power lasers (Nd:YAG and diode lasers) has been carried out. The... more
In the present study, surface engineering research related to thermally sprayed wear and corrosion resistant coatings modified by in-situ and post-treatment by novel high power lasers (Nd:YAG and diode lasers) has been carried out. The main aim of the study was to create experimental based information and knowledge on simultaneous remelting of thermally sprayed (plasma, HVOF, flame) single layers for
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... and Coat. Technol. 52, 141 (1992). 4. Krishnan R., Dash S., Babu Rao C: Scripta Materialia 45, 693 (2001). 5. Krishnan R., Dash S., Sole R., Tyagi A., Ray B.: Sur-face Eng. 18, 208 (2002). 6. Chen HC, Pfender E., Heberlein J.: Thin... more
... and Coat. Technol. 52, 141 (1992). 4. Krishnan R., Dash S., Babu Rao C: Scripta Materialia 45, 693 (2001). 5. Krishnan R., Dash S., Sole R., Tyagi A., Ray B.: Sur-face Eng. 18, 208 (2002). 6. Chen HC, Pfender E., Heberlein J.: Thin Solid Films 315, 159 (1998). ...
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ABSTRACT
In the field of surface engineering, cladding or overlay welding is a group of coating methods used in manufacturing fusion-bonded thick metallic and metal matrix composite (MMC) coatings on a wide variety of metallic base materials with... more
In the field of surface engineering, cladding or overlay welding is a group of coating methods used in manufacturing fusion-bonded thick metallic and metal matrix composite (MMC) coatings on a wide variety of metallic base materials with varying degree of deposition rate, dilution and heat input. Growing demands for more material-, energy- and cost-effective overlay welding processes as well as sustainable solutions for performance-critical applications have boosted to develop methods that are capable of producing low diluted and fusion-bonded single layer coatings with high deposition rates. Such novel cladding methods include for instance laser-based high power laser cladding, coaxial hot-wire laser cladding, laser-arc hybrid cladding, non-laser-based Cold Metal Transfer (CMT) cladding and methods that utilize high intensity infrared (IR) light. This paper introduces some of such highly innovative cladding techniques and highlights some microstructural and geometrical features, ab...
Tool steels are a class of complex carbon and alloy steels that are widely available as powders over a wide compositional range. In this work, several different tool steel grades were deposited on mild steel by the laser cladding process... more
Tool steels are a class of complex carbon and alloy steels that are widely available as powders over a wide compositional range. In this work, several different tool steel grades were deposited on mild steel by the laser cladding process using a continuous wave 4.4 kW Nd:YAG laser in combination with a coaxial powder feeding technique. With bidirectional scanning pattern, most of the grades were deposited crack-free with hardness up to 1000 HV without additional preheating. A comparative study of 3-body abrasion and single point scratch wear behaviour was conducted on the obtained coatings. In a 3-body abrasion wear study, the laser clad Ralloy WR6 with significant portion of retained austenite exhibited superior abrasive wear resistance compared with the fully martensitic tool steel coatings (M2, M4, H13, HS-23, HS-30) and the reference material, Raex Ar500 wear resistant steel. The abrasion wear resistance of austenitic-martensitic WR6 tool steel was further enhanced by the extern...
Hydraulic piston rods on oil and gas drilling platforms, hydro-power stations, chemical plants, and underground mines are exposed to severe tribo-corrosive conditions under static and dynamic me- chanical loads. Piston rods made of... more
Hydraulic piston rods on oil and gas drilling platforms, hydro-power stations, chemical plants, and underground mines are exposed to severe tribo-corrosive conditions under static and dynamic me- chanical loads. Piston rods made of carbon, quenched and tempered (QT) and stainless steels are frequently surface coated with methods such as thermal spraying, hard chrome plating, and overlay welding. Unfortunately, several premature failures have been reported particularly in marine appli- cations due to insufficient coating properties. Laser cladding has recently drawn lot of attention in this field due to high coating quality and significant improvements in productivity. In this study, several potential Fe-, Ni-, and Co-based alloys were laser clad on carbon and QT steels. Their cor- rosion and mechanical performances were explored in long-term salt spray, immersion, hardness, abrasive wear, and four-point bending fatigue tests. Most of the laser coatings outperformed hard chrome in corro...
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ABSTRACT
ABSTRACT Fatigue cracking of laser clad cylindrical and square section bars depends upon a variety of factors. This paper presents Finite Element Analysis (FEA) of the different macro stress fields generated as well as stress raisers... more
ABSTRACT Fatigue cracking of laser clad cylindrical and square section bars depends upon a variety of factors. This paper presents Finite Element Analysis (FEA) of the different macro stress fields generated as well as stress raisers created by laser cladding defects for four different fatigue load conditions. As important as the defect types are their locations and orientations, categorized into zero-, one- and two-dimensional defects. Pores and inclusions become critical close to surfaces. The performance of as-clad surfaces can be governed by the sharpness of surface notches and planar defects like hot cracks or lack-of-fusion (LOF) are most critical if oriented vertically, transverse to the bar axis. The combination of the macro stress field with the defect type and its position and orientation determines whether it is the most critical stress raiser. Based on calculated cases, quantitative and qualitative charts were developed as guidelines to visualize the trends of different combinations.