Showing papers on "Spray forming published in 2014"

Formation of Fe-based glassy matrix composite coatings by laser processing

Abstract: Coatings of a Fe43.2Co28.8B19.2Nb4Si4.8 alloy on AISI 1020 steel substrates were produced by laser cladding. By properly selecting the processing parameters adherent tracks with negligible dilution could be obtained. For the processing conditions used the clad material presents a graded structure consisting of 5 layers with different microstructures, resulting from the prevalent material solidification path. Solidification starts by epitaxial growth of Fe–Co δ-ferrite on the δ-ferrite resulting from heating of the substrate near the fusion line into the δ-ferrite stability temperature range. This first stage of solidification leads to the formation of consecutive layers consisting predominantly of δ-ferrite and formed by plane front, cellular and columnar dendritic solidification. The solidification of Fe–Co δ-ferrite leads to the segregation of B and Nb first frontally, to the bulk of the liquid, then to the interdendritic regions, resulting in the precipitation of a boride containing eutectic. Initially, the eutectic precipitates in the interdendritic regions, resulting in a layer of material comprised of δ-ferrite dendrites and interdendritic eutectic, then in a layer of material where the eutectic is the bulk alloy constituent. Eventually, a layer of amorphous material with homogeneously dispersed dendrites of Fe–Co δ-ferrite forms in most of the coating thickness. These embedded dendrites form by equiaxed solidification within the supercooled liquid at the trailing edge of the melt pool, from δ-ferrite dendrite fragments and boride particles carried from the growing columnar layer into the liquid bulk by Marangoni convection, driven by the temperature gradients existing within the melt pool. They play a critical role in defining the excellent properties of the coating material: a very high hardness of 1040 ± 16 HV0.5 associated to a reasonable ductility, allowing the formation of crack-free coatings, in contrast with the bulk alloy prepared by spray forming, either in the as-prepared condition or after laser melting.

Warm Spray Forming of Ti-6Al-4V

Abstract: Warm spray (WS) is a modification of high-velocity oxy-fuel spraying, in which the temperature of the supersonic gas flow generated by the combustion of kerosene and oxygen is controlled by diluting the combustion flame with an inert gas such as nitrogen. The inert gas is injected into the mixing chamber placed between the combustion chamber and the powder feed ports, thus the temperature of the propellant gas can be controlled from ~700 to 2,000 K. Since WS allows for higher particle temperatures in comparison to cold spray, warm sprayed particles are more softened upon impact, thus resulting in greater deformation facilitating the formation of shear instability for bonding. Recently, the combustion pressure of WS has been increased from 1 (low-pressure warm spray) to 4 MPa (high-pressure warm spray) in order to increase the velocity of sprayed particles. Effects of spray parameters on microstructure, mechanical properties, and splats formation of Ti-6Al-4V were systematically studied. Obtained coatings were examined by analyzing the coating cross-section images, microhardness as well as oxygen content. In addition, flattening ratio of splats was calculated as a function of nitrogen flow rate. It was found that the increased particle velocity caused by the increased combustion pressure had significant beneficial effects in terms of improving density and controlling the oxygen level in the sprayed Ti-6Al-4V coatings.

Wear Behavior of Disk Shape Spray Formed Al-Si-Pb Alloys

Abstract: Wear behavior of spray formed Al-Si-Pb alloys was investigated using a pin on disk type wear testing machine. Wear rate behavior with applied load was observed to depict three stages, in the second stage rate of increase in wear rate was the lowest and in the third stage it was the highest. The wear rate decreased with the increase in distance from center to periphery of the spray deposit. It decreased linearly with the increase in lead content and it was lower for 12% Si as compared to that of 6% Si in Al-Si-Pb alloys. The coefficient of friction decreased rapidly up to the load of 40 N and beyond this load the friction coefficient was almost constant. The coefficient of friction was lower for higher lead content.

Material increase manufacturing method based on high-speed spray forming of multi-material particles

Abstract: The invention discloses a material increase manufacturing method based on high-speed spray forming of multi-material particles. According to the method, metal and ceramic particles are carried by means of certain compressed air and impact a substrate at a high speed after speeding up through a spray gun. When the speed of the particles exceeds a clinical depositing speed, the particles effectively deposit on the substrate or on the deposited and formed particles through mechanical impact. In the spraying forming process of the particles, the material particles do not melt, and accordingly selection of materials is not limited by melting points, and synchronous spray forming manufacturing of various materials can be achieved. A spray forming part has high compactness and can achieve unique mechanical, physical and chemical performance. Material increase manufacturing of three-dimensional functional parts which have complex space structures, controllable material distribution and micro structures is achieved through a multi-freedom-degree spray device. The process is simple, environmentally-friendly, low in energy consumption, strong in operability and capable of solving the difficult problem that multi-material functional parts with composite structures cannot be manufactured through a traditional quick forming process.

Materials characterization and mechanical properties of graded tool steels processed by a new co-spray forming technique

Abstract: In order to meet the requirements of micro cold forming tools, a new co-spray forming process has been applied to produce graded materials from two different tool steels in this study. The two steel melts were atomized and co-sprayed simultaneously onto a flat substrate, resulting in a flat graded deposit when the two sprays were overlapped. To eliminate porosity and break up carbide network, the graded deposits were further hot rolled. The resultant graded tool steels were investigated with respect to porosity, element distribution, microstructure, hardness, strength, and toughness. The degree of overlapping of the two sprays determined the concentration gradient of the chemical elements in the deposits. The overlapping of the spray cones also contributed to low porosity in the gradient zone of the deposits. The porosity in the graded deposits could be essentially eliminated by means of hot rolling. The carbides and grain structures of the hot rolled tool steels were fine and homogeneous. By means of combining different tool steels in a single deposit, different microstructures and properties were combined.

Microstructure of a recycled AA7050 alloy processed by spray forming followed by hot extrusion and rotary swaging

Abstract: The aim of this study is to evaluate the microstructure of a recycled AA7050 alloy processed by spray forming followed by hot extrusion and swaging. Machining chips from an aircraft manufacturer were used as raw material. The microstructure was investigated by optical microscopy (MO) and scanning electronic microscopy (SEM). The spray formed deposit was homogenized at 743 K, 8 h, extruded at 693 K with a deformation rate of 0.1 s–1 and an extrusion rate of 156:1, producing a bar with 8.0 mm in diameter. Due to a specific combination of high extrusion temperature and deformation rate, partial recrystallization occurred and different grain sizes were obtained through the extruded cross section. After extrusion, the 8.0 mm bar was processed by rotary swaging in several steps up to a 2.0 mm final diameter. The resulting microstructure revealed a cold worked structure, with no recrystallization. Tensile tests were performed in both cases and the slant type of fracture reveals that Portevin Le-Chatelier effect took place in this alloy. Moreover, the efficacy of extrusion and rotary swaging parameters to reduce the porosity, intrinsic to the spray form process, was analyzed, as well the distribution of intermetallic particles.

Multi-metal liquid spray deposition additive manufacturing method

Abstract: The invention discloses a multi-metal liquid spray deposition additive manufacturing method and belongs to additive manufacturing techniques in the field of machine manufacturing The method includes: establishing a computer 3D solid model of parts, and z-directionally layering the established model to obtain a scan path of a current layer; melting various metals to be deposited into liquids with a heating device; using nozzles to perform metal liquid spray forming along the scan path of the current layer according to the information of the current layer; after spraying of one layer, moving to another layer height The multi-nozzle multi-metal spray deposition fast-forming method is adopted, the metal parts manufactured with additive manufactured by the method have good internal structure and good operating performance, production cycle is short, and production efficiency is high

Microstructures and high temperature properties of spray formed niobium-containing M3 high speed steel

Abstract: The billets of M3 high speed steel (HSS) with or without niobium addition were prepared via spray forming and forging, and the corresponding microstructures, properties were characterized and analysed. Finer and uniformly-distributed grains without macrosegregation appear in the as-deposited high speed steel that are different to the as-cast high speed steel, and the primary austenite grain size can be decreased with 2% niobium addition. Niobium appears in primary MC-type carbides to form Nb6C5 in MN2 high speed steel, whereas it contributes less to the creation of eutectic M6C-type carbides. With same treatments to forged MN2 high speed steel and M3 high speed steel, it is found that the peak hardness of these two steels are almost the same, but the temper-softening resistance of the former is better. With higher high-temperature hardness of the forged MN2 high speed steel, its temper softening above 600 °C tends to slow down, which is related to the precipitation of the secondary carbides after tempering. A satisfactory solid solubility of Vanadium and Molybdenum can be obtained by Nb substitution, precipitation strengthening induced by larger numbers of nano-scaled MC and M2C secondary carbides accounts for the primary role of determining higher hardness of MN2 high speed steel. The results of the wear tests show that the abrasive and adhesive wear resistance of MN2 high speed steel can be improved by the grain refinement, existence of harder niobium-containing MC carbides, as well as solute strengthening by more solute atoms. The oxidational wear behavior of MN2 high speed steel can be markedly influenced by the presence of the high hardness and stabilization of primary niobium-containing MC-type carbides embedded in the matrix tested at 500 °C or increased loads. The primary MC carbides with much finer sizes and uniform distribution induced by the combined effects of niobium addition and atomization/deposition would be greatly responsible for the good friction performance of the forged MN2 high speed steel.

Rapid solidification aluminum alloy material and preparation method thereof

Abstract: The invention relates to a rapid solidification aluminum alloy material and a preparation method thereof. The aluminum alloy material comprises 6-10wt% of iron, 2-6wt% of mischmetal and the balance of aluminium and inevitable impurities. The preparation method comprises the following steps: smelting to obtain Al-Fe intermediate alloy and Al-Re intermediate alloy; smelting pure aluminium ingots, the Al-Fe intermediate alloy and the Al-Re intermediate alloy, then pouring, cooling, demolding so as to obtain an aluminium alloy cast ingot comprising the 6-10wt% of iron and the 2-6w% of mischmetal; crushing and cleaning the alloy ingot; carrying out spray forming so as to prepare the aluminium alloy round ingot; carrying out hot-pressing densification on the aluminium alloy round ingot so as to obtain the densification spraying deposition aluminium alloy which is the rapid solidification aluminum alloy material. Compared with the prior art, the rapid solidification aluminum alloy material prepared by the method has relatively high strength and thermal stability and is mainly used for battery current collector materials and equipment used in high-temperature corrosion environments.

Super-strength high-toughness magnesium alloy material and preparation method thereof

Abstract: The invention provides a super-strength high-toughness magnesium alloy material and a preparation method thereof. The alloy comprises the following components of 7-10wt% of Gd, 3.5-5.8wt% of Y, 1.7-3.5wt% of Zn, 0.3 to 1.wt% of Zr, and the balance of Mg; and the magnesium alloy material is prepared by the spray forming method. The preparation method comprises the following steps of: batching the alloy components in percentage by weight; preparing a prealloyed ingot; melting the prealloyed ingot; atomizing with an atomizing nozzle and downwards pulling a receiving tray at the same time, wherein the receiving tray is pulled by a variable frequency motor to rotate at a high speed when an ingot blank is pulled down by the receiving tray; preparing an alloy ingot by the inclined spray and straight pulling method; performing deformation processing for the alloy ingot to obtain the required part blank; and thermally processing the part blank to obtain the final part. The material alloy has accurate components, an uniform and fine microscopic structure, and no obvious defect and macrosegregation, and is outstanding in thermal deformation processing capability; the ultimate tensile strength is more than 550MPa; in addition, the alloy material remains relatively high plasticity; and the fracture toughness property is also outstanding, so that the safety of a part can be improved.

Preparation method of high-silicon aluminum alloy

Abstract: The invention relates to a preparation method of an aluminum alloy material, and particularly relates to a preparation method of a high-silicon aluminum alloy. The method comprises the following steps: 1) melting quantitative pure aluminum in an intermediate frequency furnace and heating to 800-900 DEG C, adding half of the required amount of express-melting silicon according to the required silicon content in Al70Si, further heating to a temperature of 100 DEG C over the melting point of the alloy, adding 3/8 of the required amount of the express-melting silicon to allow the content of the silicon to be 65% in the alloy by weight, and discharging to obtain an alloy blank; 2) adding the alloy blank into the intermediate frequency furnace, heating to obtain alloy liquid at 1,300 DEG C, transferring into spray forming equipment, adjusting the temperature of the alloy liquid to 1,200 DEG C, enabling the alloy liquid to flow into an atomizer, atomizing with high-pressure nitrogen, and then depositing on a substrate to obtain an alloy ingot. By adopting the method provided by the invention, the alloy liquid can quickly meet the technological requirements of spray forming while ensuring accurate and controllable alloy content; moreover, a high-performance silicon aluminum alloy material meeting the requirements of electronic packaging in the properties such as expansion coefficient, thermal conductivity, material strength and the like can be obtained.

Spray Forming of MMCs

Abstract: This article provides a comprehensive review on metal matrix composites (MMCs) produced via spray forming. First, the principles, characteristics, and applications of spray forming are presented, which is considered as a prerequisite to discuss spray forming of MMCs. Then, spray forming techniques in the fabrication of MMCs are systematically reviewed. Next, microstructural characteristics and physical/mechanical properties of spray-formed MMCs are described. Finally, the mechanisms involved during spray forming are analyzed.

Study of the Influence of Silicon Phase Morphology on the Microstructural Stress Distribution in Al–Si Alloys Using Object Oriented Finite Element Modeling

Abstract: Near-eutectic Al–Si alloys were produced by conventional casting and spray forming resulting in microstructural differences due to process dependent cooling rates. The as-sprayed alloy exhibited fine equiaxed Si particles uniformly distributed throughout the matrix in contrast to the as-cast alloy, which exhibited acicular morphology with relatively large needle-like Si particles. The effect of Si morphology on the microstructural stress distribution of the as-cast and as-sprayed alloys was estimated by simulating uni-axial tensile loads on microstructures using Object Oriented Finite Element code (OOF2). Microstructures of the as-sprayed alloy experienced relatively low and uniform stress distribution, while the microstructural stress distribution in the as-cast alloy was significantly influenced by the orientation of the needle shaped silicon particles.

Method for manufacturing additives based on synchronous spray and adhesion

Abstract: The invention discloses a method for manufacturing additives based on synchronous spray and adhesion. The method includes the steps that according to the requirement for the appearance of a part to be formed, a three-dimensional model of the part to be formed is established, and hierarchical processing is conducted according to the machining direction; according to the requirement of the three-dimensional model for the number of base materials and adhesives, base material particles and the adhesives are placed in a powder feeder and an adhesive container respectively, compressed air directly carries the base material particles from the powder feeder without preheating and then conveys the base material particles to a base material spray gun, and meanwhile an adhesive spray gun is controlled to spray the adhesives to conduct adhesive solidification on the base materials; according to the shape of each layer section of the three-dimensional model, relative motion of the spray guns and a platform is controlled, and layer-by-layer multi-material controllable spray forming is conducted; after spray and adhesive forming of the part to be formed, a small number of particle materials which do not adhere to the surface and the internal structure are removed, and a final part to be formed is formed. According to the method, spray of the base materials and spray of the adhesives for adhesive solidification can be conducted at the same time, and the method has the advantages that the base materials are saved, cleaning is easy to conduct, energy is saved and emission is reduced.

Development of low-melting-point filler materials for laser beam brazing of aluminum alloys Entwicklung von Lötdrähten mit niedriger Schmelztemperatur für das Laserstrahllöten von Aluminium

Abstract: In order to develop low-melting-point filler materials for laser beam brazing of aluminum alloys, Al–Si–Cu based alloys and Al–Si–Zn based alloys were produced via spray forming and associated deformation processes. The selected alloys were spray formed in the form of billet with a diameter around 160 mm and hot extruded into wire rods with a diameter of 8 mm. The extrusions were further cold worked into thin wires with a diameter of 1.2 mm via rotary swaging. Finally, the filler wires were applied in the laser beam brazing of AA6082 structures. It showed that the newly developed filler materials could meet the requirements of the laser beam brazing of aluminum alloys. Particularly, the laser beam brazing process using the sprayformed filler materials required a significantly lower energy input and allowed for higher brazing speed as compared to the conventional AlSi12 filler material.

Spray-Formed Bearing Steel with High Oxide Cleanliness and Small and Fine Dispersed Inclusions*

Abstract: Rolling contact bearings belong to the most highly-stressed components in mechanical engineering. This demands high quality of the bearing steels, especially high-fatigue strength. Today b...

Analyse eines durch das Co-Spray-Verfahren hergestellten Werkzeuges zur Warmumformung

Abstract: In the industrial manufacturing chain of roller bearings the hot bars are subsequently sheared into billets and these are automatically transported to the first forming stage of the press. Normally the cobalt-based hard-facing alloys for the blades are deposited by manual metal arc or plasma transfer arc welding. In the research work presented here, the hard-facing alloys are produced by spray forming to increase the life time of the tool. Long life time is expected because of the advantages of spray forming: homogeneity of the microstructure, a low segregation and absence of a heat affected welding zone. For this purpose a bi-metal composite is deposited in a co-spray process to combine the hard-facing alloy layer with a hot working steel to insert the blade into a carrier. The interface between the two different materials was analyzed in terms of porosity, hardness, adhesive strength and machinability to describe the new composite material.

Bulk synthesis of amorphous and nano-crystalline materials by spray forming

Abstract: Bulk amorphous and nano-crystalline metallic materials have been observed to possess excellent mechanical and physical properties. The conventional process routes, to synthesize such materials, are restricted by their ability to achieve rapid solidification, which limits the dimensions of the materials produced. In the last 10-12 years, spray forming has been employed to avoid these limitations by using its capability of layer by layer deposition of undercooled droplets. The current literature indicates that the opportunities provided by this process can be effectively utilized to produce bulk materials in a single step. In this paper, an attempt has been made to bring out the developments in the synthesis of bulk amorphous and/or nano-crystalline materials by spray forming. The effect of process parameters, droplet size distribution in the atomized spray, the thermal conditions of droplets prior to deposition and the deposition surface conditions have been discussed. It has been demonstrate that a layer by layer deposition of undercooled droplets of glass forming alloys on a relatively cold deposition surface is the suitable condition to achieve bulk amorphous/nano-crystalline materials.

Influence of Hot Isostatic Pressing on the Microstructure and Mechanical Properties of a Spray-Formed Al-4.5 wt.% Cu Alloy

Abstract: Al-4.5 wt.% Cu alloy was spray atomized and deposited at varied spray heights ranging from 300 to 390 mm. The average grain sizes decreased from ~ 29 to ~ 18 μm and a concomitant increase in the hardness and the 0.2% yield strength (YS) with increase in the spray height. The respective hardness values of SF-300, SF-340, and SF-390 are 451 ± 59, 530 ± 39, and 726 ± 39 MPa and the YS are 108 ± 7, 115 ± 8, and 159 ± 10 MPa. The transmission electron micrographs revealed the morphological changes of the Al2Cu phase from irregular shaped to small plate-shaped and then subsequently to spheroidal shape due to high undercooling encountered during spray atomization with increase in spray height from 300 to 390 mm. The porosity of the spray formed deposits varied between 5 to 12%. Hot isostatic pressing of spray deposits reduced the porosity to less than 0.5% without any appreciable increase in grain size. A dislocation creep mechanism seems to be operative during the secondary processing. A comparison between as-spray formed and hot isostatically pressed deposits exemplifies improvement in mechanical properties as a result of elimination of porosity without affecting the fine grain sizes achieved during the spray-forming process.

Microstructure Characterization and Kinetics of Crystallization Behavior of Tubular Spray Formed Fe43.2Co28.8B19.2Si4.8Nb4 Bulk Metallic Glass

Abstract: In this study the Fe432Co288B192Si48Nb4 (at%) alloy was processed by spray forming in an industrial facility with the aim of investigating the formation of amorphous phases The thicker layers (5–15 mm) presented partial/fully crystalline microstructure with onset of crystallization of the amorphous phase at Tx = 595 °C On the other hand, thinner layers (below 25 mm) presented fully amorphous structure, and glassy behaviour with glass transition (Tg) at 555 °C The thermal stability and the crystallization kinetics of the alloy were studied using the isothermal DSC curves, measured at different heating rates and temperatures Despite its good glass-forming ability (GFA) and high stability against crystallizations, its incubation time for crystallization is almost zero In order to rule-out the complete crystallization mechanism, in situ temperature resolved studies using TEM were done In addition, the amorphous part of the deposit was heat treated at various temperatures/times and the res

Research on the Second Phase of Spray Forming Al-8.5Fe-1.3V-1.7Si Aluminum Alloy

Abstract: Heat-resistant Al-8.5Fe-1.3V-1.7Si aluminum alloys were prepared by spray forming technique. The phase transition of deposited alloys from room temperature to 500°C was measured by Differential Scanning Calorimeter. The organization and the second phases of the alloys were observed and studied by transmission electron microscopy. The research results show that No endothermic peak appears in the deposited alloys during heating process, there is no phase transition occur in the alloy during the heating process from room temperature to 500°C. The deposited alloys mainly include α-Al and α-Al12(Fe,V)3Si phase. Under the transmission electron microscopy, there are also a small amount of slug, fan-shaped, needle-like, block, strip second phases, these phases are Al12Fe3Si, Al8Fe2Si, θ-Al13Fe4, Al9FeSi3, Al6Fe.