The Experts below are selected from a list of 5256 Experts worldwide ranked by ideXlab platform
Claudemiro Bolfarini - One of the best experts on this subject based on the ideXlab platform.
-
Wear Resistant Duplex Stainless Steels Produced by Spray Forming
Metals and Materials International, 2018Co-Authors: Juliano Soyama, Claudio Shyinti Kiminami, Thiago Pama Lopes, Guilherme Zepon, Walter José Botta, Claudemiro BolfariniAbstract:In this work, boron-modified duplex stainless steels were prepared by Spray Forming using design guidelines provided by thermodynamic calculations. Firstly, an investigation of stable phases and phase formation sequence in duplex steels containing high levels of boron was conducted. The calculation indicated that there was an eutectic point at around 1 wt% boron with different primary phase formations upon equilibrium solidification. For hypoeutectic compositions, the primary phase was δ-Ferrite, whereas for hypereutectic a metallic boride (M2B) should form. Additionally, eutectic reactions for both compositions should lead to the formation of borides M2B and M3B2. Secondly, Spray Forming experiments were conducted based on the thermodynamic calculations. Sample preparation was carried out using a conventional superduplex steel (2507) as starting material. Two different compositions were selected: one hypoeutectic (0.8 wt% B) and one hypereutectic (2.5 wt% B). The microstructural investigation revealed the formation of different types of borides embedded in an austenitic-ferritic matrix. Finally, the wear resistance was evaluated with the dry sand/rubber wheel test and a significant improvement was observed for boron-containing steels in comparison with the same steel without boron. This improvement was attributed to the presence of fine and well-distributed boride particles that protected the austenitic-ferritic matrix from material removal.
-
design of wear resistant boron modified supermartensitic stainless steel by Spray Forming process
Materials & Design, 2015Co-Authors: Guilherme Zepon, A H Kasama, Claudio Shyinti Kiminami, Walter José Botta, Alexandre Romao Costa Nascimento, R P Nogueira, Claudemiro BolfariniAbstract:Abstract In this paper the chemical composition of the supermartensitic stainless (SM) was modified with the addition of small boron contents (0.3, 0.5 and 0.7 wt.%) and processed by Spray Forming aiming the development of functionalized stainless steel with higher wear resistance. The addition of boron to the SM leads to the formation of continuous network of M 2 B type borides uniformly distributed in the refined microstructure promoted by the Spray Forming process. The wear resistance was evaluated by two different methodologies: (1) the standardized dry sand/rubber wheel test (ASTM G65); and (2) a plate-on-cylinder (POC) wear test which was designed to simulate in laboratorial scale the tribosystems found in wear of risers and casings. It was shown that the wear mechanisms that take place in both tests are quite different, but in all cases increasing the boron content is always accompanied by an increase in the wear resistance. Electrochemical analyses were performed to evaluate the corrosion resistance of the designed alloys. It could be seen that corrosion properties similar to the commercial SM can be achieved in the SM modified with 0.7 wt.% of boron if an over content of chromium is added to the chemical composition.
-
Spray Forming of cu 11 85al 3 2ni 3mn wt shape memory alloy
Journal of Alloys and Compounds, 2014Co-Authors: R D Cava, Claudio Shyinti Kiminami, Claudemiro Bolfarini, E M Mazzer, Walter Jose Botta Filho, Piter Gargarella, Jurger EckertAbstract:Abstract Cu-based shape memory alloys (SMA) in the range of Cu–(11.8–13.5)Al–(3.2–4)Ni–(2–3)Mn (wt%) exhibit high thermal and electrical conductivity, combine good mechanical properties with a pronounced shape memory effect, and are low cost (Dutkiewicz et al., 1999). Their processing requires high cooling rates to reduce grain size, prevent decomposition of the s phase into equilibrium phases, and induce martensite transformation. In this investigation, Cu–11.85Al–3.2Ni–3Mn (wt%) shape memory alloy was processed by Spray Forming, a rapid solidification technique that involves cooling rates of 10 1 to 10 4 K/s, to determine the potential of producing deposits with adequate microstructure, homogeneity and porosity for the manufacture of SMA near net shape parts. To this end, 5.2 kg of alloy with nominal composition was atomized with nitrogen gas under a pressure of 0.5 MPa and a gas–metal ratio (GMR) of 1.93. The atomized material was deposited at 60 rpm on a rotating steel substrate positioned 350 mm below the gas nozzle. The microstructure of the deposit was characterized by optical and scanning electron microscopy, X-ray diffraction and differential scanning calorimetry. The deposit with an effective diameter of 240 mm and 75 mm height presented equiaxial grains with a martensite microstructure. Grain sizes varied from 25 μm in the lower region (contact with the steel substrate) to 160 μm in the upper region of the deposit. Measurements of the reverse martensite transformation temperature of the deposit in different regions revealed its strong influence on the grain size.
-
microstructure evolution and mechanical properties of al zn mg cu alloy reprocessed by Spray Forming and heat treated at peak aged condition
Journal of Alloys and Compounds, 2013Co-Authors: E M Mazzer, Claudio Shyinti Kiminami, Conrado Ramos Moreira Afonso, M Galano, Claudemiro BolfariniAbstract:Abstract Machining chips of the alloy AA7050 were reprocessed by Spray Forming followed by hot-extrusion and heat treatment. The Spray-formed deposit presented a microstructure with hardening η′ precipitates within the matrix and equilibrium η precipitates at the grain boundaries, refined grains and low segregation of the main elements Zn, Cu and Mg. The final microstructure at peak aged condition is mainly composed by Guinier–Preston (GP) zones, η′ metastable, η equilibrium , Al3Zr dispersoids and the coarse Al7Cu2Fe intermetallic. A well-defined precipitation free zone along grain boundaries was not observed. Good mechanical properties were achieved.
-
microstructure study of al 7050 alloy reprocessed by Spray Forming and hot extrusion and aged at 121 c
Intermetallics, 2013Co-Authors: E M Mazzer, Claudemiro Bolfarini, Conrado Ramos Moreira Afonso, Claudio Shyinti KiminamiAbstract:Abstract In this study, machined chips of Al 7050 alloy derived from the aeronautic industry were reprocessed by Spray Forming technique and hot extrusion. The microstructures and hardness of the deposit and their subsequent development resulting from heat treatment and hot extrusion were investigated. The results show that Spray Forming contributed to providing a refined and homogeneous microstructure after aging heat treatment at 121 °C for 16 h due to a homogeneous distribution of the hardening η′ metastable phase.
Claudio Shyinti Kiminami - One of the best experts on this subject based on the ideXlab platform.
-
Wear Resistant Duplex Stainless Steels Produced by Spray Forming
Metals and Materials International, 2018Co-Authors: Juliano Soyama, Claudio Shyinti Kiminami, Thiago Pama Lopes, Guilherme Zepon, Walter José Botta, Claudemiro BolfariniAbstract:In this work, boron-modified duplex stainless steels were prepared by Spray Forming using design guidelines provided by thermodynamic calculations. Firstly, an investigation of stable phases and phase formation sequence in duplex steels containing high levels of boron was conducted. The calculation indicated that there was an eutectic point at around 1 wt% boron with different primary phase formations upon equilibrium solidification. For hypoeutectic compositions, the primary phase was δ-Ferrite, whereas for hypereutectic a metallic boride (M2B) should form. Additionally, eutectic reactions for both compositions should lead to the formation of borides M2B and M3B2. Secondly, Spray Forming experiments were conducted based on the thermodynamic calculations. Sample preparation was carried out using a conventional superduplex steel (2507) as starting material. Two different compositions were selected: one hypoeutectic (0.8 wt% B) and one hypereutectic (2.5 wt% B). The microstructural investigation revealed the formation of different types of borides embedded in an austenitic-ferritic matrix. Finally, the wear resistance was evaluated with the dry sand/rubber wheel test and a significant improvement was observed for boron-containing steels in comparison with the same steel without boron. This improvement was attributed to the presence of fine and well-distributed boride particles that protected the austenitic-ferritic matrix from material removal.
-
design of wear resistant boron modified supermartensitic stainless steel by Spray Forming process
Materials & Design, 2015Co-Authors: Guilherme Zepon, A H Kasama, Claudio Shyinti Kiminami, Walter José Botta, Alexandre Romao Costa Nascimento, R P Nogueira, Claudemiro BolfariniAbstract:Abstract In this paper the chemical composition of the supermartensitic stainless (SM) was modified with the addition of small boron contents (0.3, 0.5 and 0.7 wt.%) and processed by Spray Forming aiming the development of functionalized stainless steel with higher wear resistance. The addition of boron to the SM leads to the formation of continuous network of M 2 B type borides uniformly distributed in the refined microstructure promoted by the Spray Forming process. The wear resistance was evaluated by two different methodologies: (1) the standardized dry sand/rubber wheel test (ASTM G65); and (2) a plate-on-cylinder (POC) wear test which was designed to simulate in laboratorial scale the tribosystems found in wear of risers and casings. It was shown that the wear mechanisms that take place in both tests are quite different, but in all cases increasing the boron content is always accompanied by an increase in the wear resistance. Electrochemical analyses were performed to evaluate the corrosion resistance of the designed alloys. It could be seen that corrosion properties similar to the commercial SM can be achieved in the SM modified with 0.7 wt.% of boron if an over content of chromium is added to the chemical composition.
-
Spray Forming of cu 11 85al 3 2ni 3mn wt shape memory alloy
Journal of Alloys and Compounds, 2014Co-Authors: R D Cava, Claudio Shyinti Kiminami, Claudemiro Bolfarini, E M Mazzer, Walter Jose Botta Filho, Piter Gargarella, Jurger EckertAbstract:Abstract Cu-based shape memory alloys (SMA) in the range of Cu–(11.8–13.5)Al–(3.2–4)Ni–(2–3)Mn (wt%) exhibit high thermal and electrical conductivity, combine good mechanical properties with a pronounced shape memory effect, and are low cost (Dutkiewicz et al., 1999). Their processing requires high cooling rates to reduce grain size, prevent decomposition of the s phase into equilibrium phases, and induce martensite transformation. In this investigation, Cu–11.85Al–3.2Ni–3Mn (wt%) shape memory alloy was processed by Spray Forming, a rapid solidification technique that involves cooling rates of 10 1 to 10 4 K/s, to determine the potential of producing deposits with adequate microstructure, homogeneity and porosity for the manufacture of SMA near net shape parts. To this end, 5.2 kg of alloy with nominal composition was atomized with nitrogen gas under a pressure of 0.5 MPa and a gas–metal ratio (GMR) of 1.93. The atomized material was deposited at 60 rpm on a rotating steel substrate positioned 350 mm below the gas nozzle. The microstructure of the deposit was characterized by optical and scanning electron microscopy, X-ray diffraction and differential scanning calorimetry. The deposit with an effective diameter of 240 mm and 75 mm height presented equiaxial grains with a martensite microstructure. Grain sizes varied from 25 μm in the lower region (contact with the steel substrate) to 160 μm in the upper region of the deposit. Measurements of the reverse martensite transformation temperature of the deposit in different regions revealed its strong influence on the grain size.
-
microstructure evolution and mechanical properties of al zn mg cu alloy reprocessed by Spray Forming and heat treated at peak aged condition
Journal of Alloys and Compounds, 2013Co-Authors: E M Mazzer, Claudio Shyinti Kiminami, Conrado Ramos Moreira Afonso, M Galano, Claudemiro BolfariniAbstract:Abstract Machining chips of the alloy AA7050 were reprocessed by Spray Forming followed by hot-extrusion and heat treatment. The Spray-formed deposit presented a microstructure with hardening η′ precipitates within the matrix and equilibrium η precipitates at the grain boundaries, refined grains and low segregation of the main elements Zn, Cu and Mg. The final microstructure at peak aged condition is mainly composed by Guinier–Preston (GP) zones, η′ metastable, η equilibrium , Al3Zr dispersoids and the coarse Al7Cu2Fe intermetallic. A well-defined precipitation free zone along grain boundaries was not observed. Good mechanical properties were achieved.
-
microstructure study of al 7050 alloy reprocessed by Spray Forming and hot extrusion and aged at 121 c
Intermetallics, 2013Co-Authors: E M Mazzer, Claudemiro Bolfarini, Conrado Ramos Moreira Afonso, Claudio Shyinti KiminamiAbstract:Abstract In this study, machined chips of Al 7050 alloy derived from the aeronautic industry were reprocessed by Spray Forming technique and hot extrusion. The microstructures and hardness of the deposit and their subsequent development resulting from heat treatment and hot extrusion were investigated. The results show that Spray Forming contributed to providing a refined and homogeneous microstructure after aging heat treatment at 121 °C for 16 h due to a homogeneous distribution of the hardening η′ metastable phase.
P S Grant - One of the best experts on this subject based on the ideXlab platform.
-
microstructural evolution in Spray Forming
Metal Sprays and Spray Deposition, 2017Co-Authors: P S Grant, Guilherme Zepon, N Ellendt, Volker UhlenwinkelAbstract:Spray Forming is a casting process in which the molten metal is directly converted to a solid bulk with unique characteristics. When processed under optimum conditions, Spray formed materials typically present microstructures composed of refined polygonal (non-dendritic) grains, uniformly distributed with low levels of micro- and macro-segregation. This set of characteristics is achieved regardless of the alloy system, making Spray Forming an attractive process to produce alloys where processing by conventional casting techniques is complicated. This chapter is dedicated to presenting the mechanisms that take place when the atomized droplets arrive at the deposit surface, and how the Spray-formed microstructures evolve during deposition. It will be seen that Spray Forming is a self grain-refining casting process and cannot be considered a rapid solidification technique. Section 7.6 will address the main differences between the microstructural evolution in Spray Forming and other Spray deposition or “thermal Spray” processes. These processes include plasma Spraying, high velocity oxy-fuel, wire arc Spraying, detonation gun Spraying, etc. In this way, it will show why Spray Forming is such a unique process. This chapter is also dedicated to presenting how the porosity—an intrinsic feature of Spray-formed microstructures—is generated and how the processing parameters affect its type, size and distribution. Furthermore, the generation of other defects related to the solidification and/or to the cooling of the Spray formed product after deposition—such as residual stresses and hot cracks—and their influence on the product quality and material properties will be presented. Finally, this chapter will also discuss the effect of the atomization gas (Ar, N2 or He) on the final product quality in terms of porosity and chemical composition of steels, superalloys, and copper alloys.
-
a hybrid arc Spray Forming technique for the manufacture of nickel superalloy in617
Materialwissenschaft Und Werkstofftechnik, 2014Co-Authors: A Sato, M Taneike, I Okada, P S GrantAbstract:Spray Forming produces cast microstructures with comparatively low macro- and micro-structural chemical segregation and is thus well-suited for the manufacture of complex chemistry, multi-component alloys that otherwise show strong elemental segregation. Although Spray formed Ni superalloys have shown properties equivalent or superior to their conventionally cast/wrought counterparts, they have not been adopted commercially because of the difficulties in ensuring a high process yield and the complexity and associated cost of large-scale Ni superalloy melting. In this paper, we describe a hybrid arc Spray Forming (HASF) process in which costly, large-scale alloy melting as pre-cursor to Spray Forming is avoided by the use of a consumable wire feedstock. To achieve thermal conditions of melt Spray Forming – essential to produce a refined, polygonal grain structure – a customised secondary atomisation system has been developed. Fe-0.8 wt%C and Ni superalloy IN617 microstructures and preliminary mechanical properties suggested that hybrid arc Spray Forming may offer an attractive combination of convenience, low cost and mechanical performance.
-
Spray Forming of bulk ultrafine grained al fe cr ti
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2010Co-Authors: C Banjongprasert, Simon C Hogg, E Liotti, Caroline A Kirk, S P Thompson, P S GrantAbstract:An Al-2.7Fe-1.9Cr-1.8Ti alloy has been Spray formed in bulk and the microstructure and properties compared with those of similar alloys produced by casting, powder aomization (PA), and mechanical alloying (MA) routes. In PA and MA routes, a nanoscale metastable icosahedral phase is usually formed and is known to confer high tensile strength. Unlike previous studies of the Spray Forming of similar Al-based metastable phase containing alloys that were restricted to small billets with high porosity, standard Spray Forming conditions were used here to produce a ~98 pct dense 19-kg billet that was hot isostatically pressed (“HIPed”), forged, and/or extruded. The microstructure has been investigated at all stages of processing using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and synchrotron X-ray diffraction (XRD) at the Diamond Light Source. Consistent with the relatively low cooling rate in Spray Forming under standard conditions, the microstructure showed no compelling evidence for the formation of metastable icosahedral phases. Nonetheless, after downstream processing, the Spray-formed mechanical properties as a function of temperature were very similar to both PA rapid solidification (RS) materials and those made by MA. These aspects have been rationalized in terms of the typical phases, defects, and residual strains produced in each process route.
-
modeling the deposition dynamics of a twin atomizer Spray Forming system
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2010Co-Authors: G Zhang, Y Zhang, P S GrantAbstract:A numerical study of the deposition dynamics of twin-atomizer Spray-Forming of large-diameter billets is presented with a focus on the coupled effect of the twin-atomizer scan frequency and substrate rotation frequency. The common period of the two frequencies ξ was the dominant parameter to govern the deposited droplet mass and billet shape. When ξ ≥ 10, a uniform mass distribution at the deposition surface was predicted, and the calculated shape agreed with experiments.
-
modelling the shape and thermal dynamics of ni superalloy rings during Spray Forming part 1 shape modelling droplet deposition splashing and redeposition
Acta Materialia, 2008Co-Authors: P S GrantAbstract:A numerical model has been developed to simulate the dynamic shape evolution of Ni superalloy rings during Spray Forming. The model comprises: (1) a droplet primary deposition model, simulating droplet primary deposition at a deposition surface; (2) a droplet splashing model, simulating the droplet splashing/scattering behaviour; and (3) a droplet redeposition model, simulating the redeposition of the scattered droplets onto the deposition surface. The model has been validated against experiments of Spray Forming large diameter IN718 alloy rings, and for the first time, the effects of droplet splashing and redeposition on the dynamic shape evolution of Spray Forming IN718 alloy rings and the deposition yields have been investigated and quantified. The model serves as the basis for a thermal dynamic model that is described in Part 2 of this publication.
A Schulz - One of the best experts on this subject based on the ideXlab platform.
-
Spray Forming of hypereutectic al si alloys
Journal of Materials Processing Technology, 2009Co-Authors: Chengsong Cui, A Schulz, K Schimanski, Hanswerner ZochAbstract:Abstract To develop advanced aluminum alloys with high silicon content, hypereutectic aluminum silicon alloys AlSi x ( x = 18, 25, and 35 wt.%) in the form of cylindrical billet have been Spray formed under different thermal conditions. To help in Spray Forming parameter selection and interpretation of experimental results, phase diagram of the alloys and their thermochemical data such as liquid fractions and enthalpies in function of temperature have been calculated. The Spray formed hypereutectic Al–Si alloys are typically composed of refined and uniformly distributed primary silicon and modified eutectic. Thermal conditions and silicon content of the deposited materials have significant influence on the metallurgical quality of the Spray formed Al–Si alloys. Strong cooling condition is required for Spray Forming Al–Si alloys with high silicon content.
-
opportunities and challenges of Spray Forming high alloyed steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: A Schulz, Volker Uhlenwinkel, Christoph Escher, Rainer Kohlmann, Alfred Kulmburg, Maria Carmen Montero, Roland Rabitsch, Wolfgang Schutzenhofer, Domenico Stocchi, Dominique VialeAbstract:Abstract Spray Forming has proven to be a useful tool for generating high-alloyed materials. The metallurgical advantages of high solidification rates are obvious. Shortening of process chains in comparison to powder metallurgy is often discussed. To approach to some of the remaining questions, especially on the influence of process gases on Spray Forming steels, within this study high-alloyed steels with melt weights up to 150 kg are Spray formed and hot worked to semi-finished materials. Properties are analyzed in comparison to products available on the market. Cold-work tool steels with high carbon content can be Spray formed to produce materials with good wear resistance and toughness. When reducing the carbon content and the amount of hard carbides, advantage of reduced segregation becomes more apparent. On the other hand, the influence of nitrogen as an alloying element is more effective and means of control are required. When corrosion or heat resistant steels with high non-carbide bonded chromium content or other nitride Forming elements are part of the alloy, care has to be taken on controlling the dissolution of process gases and subsequent precipitation and degassing during compaction and further processing. Experiments where melt protection and atomization gas were changed from nitrogen to argon have shown significant influence of process gases on Spray Forming results and the mechanical properties of the materials in hot worked and finally heat treated condition.
-
mathematical modeling of Spray Forming process of tubular preforms part 1 shape evolution
Acta Materialia, 2005Co-Authors: Chengsong Cui, Udo Fritsching, A SchulzAbstract:A three-dimensional mathematical model, tracing the coordinates of the moving surface of a growing deposit for geometry simulation, is presented in this study. This model may be used to predict the geometry and dimensions of a growing tubular product during Spray Forming. A back face culling algorithm was incorporated into the model to check the visibility of the surface during deposition. Geometrical evolution of the tubular deposit in Spray Forming and its circumferential profiles have been investigated. The shape modeling has been validated by different algorithms and experimental investigations as well. Finally, the influence of principal Spray Forming parameters on the geometry and dimensions of tubular deposits have been studied and discussed. Based on the shape model, a numerical study of the thermal field and properties will be presented in the second part of the publication.
-
nitrogen pick up during Spray Forming of high alloyed steels and its influence on microstructure and properties of the final products
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: A Schulz, Volker Uhlenwinkel, Rainer Kohlmann, Alfred Kulmburg, C Bertrand, A Oldewurtel, R Schneider, Dominique VialeAbstract:Spray Forming is now getting established as a production route for high-alloyed steels. Tool steels for hot work, cold work and high-speed cutting applications and heat resistant steels generally contain high amounts of numerous elements including chromium, vanadium and aluminium, elements with high affinity for nitrogen. Within the Spray Forming process nitrogen is usually used as protective atmosphere as well as for gas atomization. The investigation considers nitrogen interaction with steel alloys during the Spray Forming in a closed vessel. Atmospheres with different nitrogen partial pressure are applied during the process. The microstructure of the Spray formed, hot worked and finally heat treated steels is compared. Impact strength, wear resistance and strength at elevated temperature are analysed for the tool steels with respect to the nitrogen content. During melting intensive interaction of the melt with the atmosphere occurs according to the solubility of nitrogen in the alloy and high amounts of nitrogen are picked up. As a general result for the conventional alloys under investigation in Spray formed condition this leads to reduction of toughness. This can be explained by additional precipitation of nitrides or carbonitrides. Nitrogen pick-up during Spray Forming can be avoided primarily by remelting in an argon atmosphere.
Volker Uhlenwinkel - One of the best experts on this subject based on the ideXlab platform.
-
effect of hot gas atomization on Spray Forming of steel tubes using a close coupled atomizer cca
Journal of Materials Processing Technology, 2020Co-Authors: Shohag Hussain, Chengsong Cui, Volker Uhlenwinkel, Lutz MadlerAbstract:Abstract Hot gas atomization in Spray Forming has been used for the first time to improve the quality of Spray-formed tubular deposits. This technique reduces gas consumption and produces smaller droplets than cold gas atomization. The flight velocity and cooling rate of the atomized droplets increase with increasing gas temperature. These features can further influence the quality of the Spray-formed deposits. Until now, Spray-formed tubes have not been used on industrial scale due to insufficient deposit quality in terms of porosity and bonding to the substrate. Using a close-coupled atomizer (CCA), qualitative improvements of the as-Sprayed deposits have been previously studied. In the present study, a comparative investigation is done to find the influence of hot gas atomization on the Spray Forming of the bearing steel AISI 52100 (100Cr6) using a close-coupled atomizer. The Spray-formed deposit with hot gas atomization (gas temperature about 300 °C) shows lower deposit surface temperature and smaller grain size in comparison to the deposit produced under cold gas atomization condition due to smaller droplet diameter and higher cooling rate of the droplets. Moreover, the as-Sprayed deposits under hot gas atomization show a higher relative density at a lower deposit surface temperature, which extends the process window for the flexible production of Spray-formed tubes.
-
porosity and microstructure of steel tubes Spray formed by close coupled atomizer
Journal of Materials Processing Technology, 2020Co-Authors: Shohag Hussain, Chengsong Cui, Volker Uhlenwinkel, Lutz Madler, Nicole TempleAbstract:Abstract Close-coupled atomizers (CCA) can be used to reduce the porosity of Spray-formed deposits compared to free fall atomizers (FFA), possibly due to smaller size and higher velocity of the atomized droplets. Previous studies on Spray-formed AISI 52100 (100Cr6) tubular deposits show that CCA leads to less porosity in the inner and outer surface regions of the tubular deposits. However, there are very few investigations on the thermal profiles of the Spray-formed deposits and on the influences of process conditions during Spray Forming via CCA. To provide insight into the thermal profile of the deposits, in this study in-situ measurement of the deposit surface temperature is performed by a two color pyrometer and the substrate temperature is measured by means of thermocouples. The porosity and microstructure of the Spray-formed deposits under various process conditions are investigated by means of optical microscopy and image analysis. This investigation shows that the deposit thickness has a higher influence on the deposit surface temperature than the gas to melt flow rate ratio (GMR). Higher deposit temperature results in lower porosity and larger grain size. Moreover, the deposition positions on the deposit length has an influence on the porosity. The porosity in the vicinity of the substrate is higher at the deposit end position than the deposit start position. Finally, the present study suggests an optimal deposit surface temperature range for Spray Forming of highly dense tubular deposit by CCA.
-
microstructural evolution in Spray Forming
Metal Sprays and Spray Deposition, 2017Co-Authors: P S Grant, Guilherme Zepon, N Ellendt, Volker UhlenwinkelAbstract:Spray Forming is a casting process in which the molten metal is directly converted to a solid bulk with unique characteristics. When processed under optimum conditions, Spray formed materials typically present microstructures composed of refined polygonal (non-dendritic) grains, uniformly distributed with low levels of micro- and macro-segregation. This set of characteristics is achieved regardless of the alloy system, making Spray Forming an attractive process to produce alloys where processing by conventional casting techniques is complicated. This chapter is dedicated to presenting the mechanisms that take place when the atomized droplets arrive at the deposit surface, and how the Spray-formed microstructures evolve during deposition. It will be seen that Spray Forming is a self grain-refining casting process and cannot be considered a rapid solidification technique. Section 7.6 will address the main differences between the microstructural evolution in Spray Forming and other Spray deposition or “thermal Spray” processes. These processes include plasma Spraying, high velocity oxy-fuel, wire arc Spraying, detonation gun Spraying, etc. In this way, it will show why Spray Forming is such a unique process. This chapter is also dedicated to presenting how the porosity—an intrinsic feature of Spray-formed microstructures—is generated and how the processing parameters affect its type, size and distribution. Furthermore, the generation of other defects related to the solidification and/or to the cooling of the Spray formed product after deposition—such as residual stresses and hot cracks—and their influence on the product quality and material properties will be presented. Finally, this chapter will also discuss the effect of the atomization gas (Ar, N2 or He) on the final product quality in terms of porosity and chemical composition of steels, superalloys, and copper alloys.
-
Co-Spray Forming of Gradient Deposits from Two Sprays of Different Tool Steels Using Scanning Gas Atomizers
steel research international, 2013Co-Authors: Chengsong Cui, Alwin Schulz, Volker UhlenwinkelAbstract:A co-Spray Forming process was developed to produce gradient deposits from two Sprays of different tool steels using scanning gas atomizers. The tool steel melts were atomized and co-Sprayed simultaneously onto a horizontally moving flat substrate, resulting in a flat deposit with a gradient zone between two layers of the different steels when the two Sprays were overlapped. The gradient deposits were investigated with respect to the porosity, element distributions, microstructure, and hardness. It showed that a sound deposit with a desired gradient zone could be achieved under proper processing conditions.
-
simulations of temperatures residual stresses and porosity measurements in Spray formed super alloys tubes
Superalloy 718 and Derivatives, 2012Co-Authors: Reinhard Ristau, Volker Uhlenwinkel, Andreas Becker, Reinhold KienzlerAbstract:Spray Forming is a technology to produce near net shape components and preforms. A simulation tool for the temperature distribution which incorporates all necessary sub steps (metal deposition on the substrate, heat transfer across the surface by convection and radiation) is developed to calculate residual stresses during the different process steps. The resulting temperature distribution was used to calculate the stresses during all process stages. Thermal histories of temperatures at certain positions will be shown. The dependency of the residual stress on the thermal history of the material was examined. Mainly at the interface substrate/deposit, a region with elevated porosity was observed. Porosity measurements will be presented. Introduction Spray Forming combines two distinct processes. In the first step, liquid metal is atomized into a Spray cone of droplets. The impinging droplets form a near net shape product on a substrate in the second step. In contrast to Spray formed billets, (in which the surface temperature is mostly constant) the substrate surface temperature just ahead of the Spray cone is a strong function of time. Therefore, the obtained material density or the porosity is a function of the surface temperature. Porosity measurements of super alloy rings were reported in [1]. The results show that at temperatures above 1100°C, low porosity is measured. High convection coefficients in the vicinity of the Spray cone cause a temperature increase for initially cold substrates and a temperature drop for initially hot substrates. Mathematical models for the temperature distributions in the Spray formed tubes were created [2, 3, 4, 5, 6]. A detailed analysis of heat exchange phenomena on small time scales is given by [3]. The temperature distribution in substrate and deposit act as a load for the developing residual stresses. Due to the difficulties in simulating stresses in Spray formed deposits, only a few papers have been presented [7, 8, 9]. Mechanical properties for IN718 are reported for temperatures up to 1100°C [10]. The uncertainties in the mechanical properties cover a small temperature range, from 150K to the solidus temperature of the material. The resulting stresses are mainly affected by thermal strains. Specifically, they depend on the heating and cooling rates during the Spray process, and later on post Spray conditions. Therefore, the knowledge of the temperature distribution during the Spray Forming process, as well as the behavior of temperature during heat treatment and cooling processes is of great importance in the understanding of the development of residual stresses.
