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Spray forming

About: Spray forming is a research topic. Over the lifetime, 1153 publications have been published within this topic receiving 12869 citations. The topic is also known as: spray casting & spray deposition.


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Journal ArticleDOI
TL;DR: In this article, the microstructure of rapidly solidified Al-10wt%Si-4wt%Fe alloy powder was evaluated by using a combination of X-ray diffractometry-XRD, scanning electron microscopy-SEM and energy dispersive Xray spectroscopy-EDS.
Abstract: Rapid solidification processes (RSP) like gas atomization, might be used to increase the extension of the solid solubility limits of iron and silicon in the Al matrix and therefore to increase the formation of metastable crystalline phases or even to change the morphology and chemistry intermetallic phases. In this work, the microstructure of rapidly solidified Al-10wt%Si-4wt%Fe alloy powder was evaluated by using a combination of X-ray diffractometry-XRD, scanning electron microscopy-SEM and energy dispersive X-ray spectroscopy-EDS. The alloy was atomized with argon at pressure of 1,2 MPa and the superheating temperature of the melt was about 1100 K. The gas to metal mass flow ratio was 2,05. From the equilibrium diagram and associated phase fields in the Al-rich corner of the ternary AlFeSi phase diagram, it was expected the formation of αAlFeSi intermetallic phase as the primary equilibrium phase. In addition, the α-AlFeSi grows with a non-faceted interface and its formation should be kinetically more favored than faceted-growing phases. However, XRD and SEM/EDS analysis identified monoclinic β-Al5FeSi intermetallic and, tetragonal Al9FeSi3 as the phases observed in the microstructure. The later one is not expected in equilibrium diagram at all. Both phases grow with a faceted interface. It can be concluded that the high thermal undercooling promoted by gas atomization displaced the fields of phases stability and caused the observed microstructural variation. Introduction The gas atomization and deposition process (spray forming) refers to the energetic disintegration of molten metal into micron-size droplets by high velocity gas jets. The subsequent deposition of these droplets, which are a mixture of solid, liquid and partially solidified droplets, forms a dense deposit on the substrate. Spray forming presents features of rapid solidification techniques and thus results in fine-grained microstructures, increased solid solubility, non-equilibrium phases and small sizes intermetallics [1]. To understand the microstructure evolution in the deposit or resulted microstructure after powder extrusion it is necessary to understand first the microstructure obtained in the gas atomized powder, which contributes significantly to the formation of the final microstructure of the deposit. The Al-Fe-Si ternary system has been the subject of extensive investigation in the recent past partly due to the commercial importance of the Al-rich alloys, which contains Fe and Si as impurities, and partly because of some commercial Fe-based alloys are used as magnets [2]. The rapid solidification features of gas atomization lead to a non-predicted microstructure in equilibrium diagram. The difficult to the characterization of the ternary phase in the Al-Fe-Si system has been attributed to the occurrence of a number of phases over a small composition range and their small size in the order of few micrometers [3]. The problem has been compounded because of a large number of metastable phases occurs in this system. By casting AlSi commercial alloys iron is the most deleterious impurity element since it forms large platelets of a brittle intermetallic phase known as β-AlFeSi (Al5FeSi). The morphology of this phase can be altered to a less harmful Chinese script morphology termed α-AlFeSi (Al15(Fe,Mn)3Si2) by adding certain alloying elements such as Mn, Cr and Ni. Moreover, this morphology can be changed by altering the cooling rates during solidification and the nucleation conditions of the melt. In the past, the investigations have been carried out to establish the Journal of Metastable and Nanocrystalline Materials Online: 2004-08-01 ISSN: 2297-6620, Vol. 22, pp 115-120 doi:10.4028/www.scientific.net/JMNM.22.115 © 2004 Trans Tech Publications Ltd, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications Ltd, www.scientific.net. (Semanticscholar.org-19/03/20,16:20:54) compositions, morphologies and crystal structures of a large number of ternary and binary phases that exist in this ternary system [4-6]. In the present investigation the Al-10wt%Si-4wt%Fe, has been processed by gas atomization in order to evaluate the microstructural formation of the rapidly solidified powder. The results are analyzed and discussed in respect to the non-equilibrium solidification conditions in the droplets. Experimental Procedure Pure aluminium, iron and silicon were used to obtain the desired composition of the alloy, which was melted by induction heating. Spray atomization processing of Al-10%Si-4%Fe (wt%) was carried out according to following procedure. The alloy was atomized with nitrogen. Details of the equipment used were described elsewhere [7]. Atomization pressure was set at 1.2 MPa and superheating temperature of the melt at about 1040 K. In order to reduce oxidation of the droplets, the atomization chamber was filled with inert gas. Microstructural characterization studies were conducted on the polished and etched sections of the powder by scanning electron microscopy (SEM) associated with energy dispersive X-ray microanalysis (EDS). Back-scattered electron images (BEI) were used to distinguish the presence of different phases in the microstructure, which are later more precisely identified using X-ray diffractometry (XRD), and secondary electron images (SEI) to observe the three-dimensional morphology of β-AlFeSi phase. Results and Discussions Fig 1, 2, 3 and 4 shows the microstructure of the powder. Fig. 1. SEM image of the transverse section (BEI) of a particle showing the needle-like phase density and distribution. Fig. 2. SEM image of the transverse section of the powder (BEI) showing all the formed phases. It was observed the formation of a homogeneously distributed needle-like, β-AlFeSi, (confirmed by EDS), as a primary phase, Fig. 1. At a higher magnification, Fig. 2 shows that the microstructure of the powder was formed as well by the presence of an enriched Si phase and Al(Si) solid solution phase. As observed in Fig. 1, Fig. 3 is another evidence that a great amount of primary β-AlFeSi phase was obtained employing simultaneously gas atomization process and a composition that 40μm 10μm β-AlFeSi Al(Si) Enriched Si phase 116 Journal of Metastable and Nanocrystalline Materials: Winter e-volume 2004

1 citations

01 Jan 2013
TL;DR: In this paper, the microstructure of spray formed and hot-pressed alloy has been studied for densification and the performance of spray-formed and hot pressed alloys has been evaluated.
Abstract: In the present study Al-28Si-5Cu-4Mg alloy has been spray formed and hot pressed for densification. Hot pressing refined the microstructure and reduced the porosity in the spray formed alloy from 10 to 1%. The microstructure of spray formed and hot pressed alloy exhibited equiaxed grain morphology with fine and uniform distribution of both primary and eutectic Si with fine needles of Q-Al 12 Si 7 Mg 4 Fe intermetallics and Chinese script like θ- Al 2 Cu precipitates in α-Al matrix. The size of Si particles ranged from 3–10 µm. In contrast the microstructure of as-cast alloy consisted of coarse primary and eutectic Si, long needles of Q-Al-Si-Mg-Cu-Fe phase and bright grey θ-Al 2 Cu phase in the α-Al matrix. The size of primary Si varied from 30–250 µm. The spray formed and hot pressed alloy exhibited a higher hardness compared to the as-cast alloy. The wear behavior of both the alloys, under dry sliding conditions, showed an increase in the wear rate with an increase in the load. However, the spray formed and hot pressed alloy exhibited maximum wear resistance and minimum coefficient of friction, while as-cast alloy exhibited minimum wear resistance and maximum coefficient of friction over the entire range of applied load. The high wear resistance and high hardness of spray formed and hot pressed alloy are explained in the light of its microstructural modifications induced during spray forming and subsequent hot pressing and also the topographical features of worn surfaces and morphology of debris particles.

1 citations

Journal ArticleDOI
TL;DR: In this paper, it has been found that temperature is a major factor that determines the creep properties and relevant mechanisms of spray formed (SF) superalloy GH742 in its deformed and heat treated fine grained version.
Abstract: It has been found that temperature is a major factor that determines the creep properties and relevant mechanisms of spray formed (SF) superalloy GH742 in its deformed and heat treated fine grained version. The alloy has high creep resistance at 650 and low creep resistance at 750 . In order to observe the structural changes during creep, the samples for creep tests cut after and in the course of creep tests were studied by means of OM, SEM, TEM. The creep curves and properties tested and the observations made by TEM were summarized in this paper. Preliminary results show that under different test conditions grain boundary and phases within the alloy jointly play a dominant role in creep properties and mechanisms. Introduction GH742 is a high alloyed and difficult to deform superalloy and was developed for the manufacture of heavily stressed components, such as discs, shafts etc., operating in hot section of turbine engine at temperature ranging from 550 800 . There has been extensive work on the processing of the alloy carried out in recent years, but little is known about its performance at elevated temperature, especially its creep properties and the relevant mechanisms, which are of great significance for the applications of the aeronautical superalloys. Moreover, spray formed GH742 is different from wrought and cast GH742 not only in structure but also in performance. The previous study [1] shows spray formed GH742 has much higher mechanical properties at room temperature than the wrought GH742 alloy. Hence, further investigation on its mechanical properties at elevated temperature is of significant value. In the present study, a unique microstructure of spray formed GH742 was acquired through a chosen heat treatment. The creep properties of the alloy under different test conditions were investigated and compared with those of wrought GH742. Meanwhile, the creep curves were plotted in order to accurately describe the deformation process of the alloy. Associated with the above results, detailed microstructure observation by TEM was carried out to evaluate and clarify the relevant creep mechanisms. Experimental Procedure The material used was SF GH742. It has a Ni-10C-15Cr matrix containing 5% Mo and 2.7% for each of Al, Ti, Nb. Samples were cut from the preforms prepared by a series of processes, including spray forming (SF), HIP, hot forging (HF). The test bars were heat treated at 1080 /8h/a.c + 760 /16h/a.c, and machined to a gauge length of 25mm and diameter of 5mm. The creep tests were conducted on мп-3г type machine under two conditions: 1. 650 (~0.58Tm--melting temperature)/735MPa; 2. 750 (~0.65Tm)/450MPa. The strains were measured every 15 min at primary creep stage and every hour at steady creep stage for both test conditions before reached 100h. The TEM observations were carried out on JEOL2010 and JEM 2000FX, using thinned foils cut from the test bars longitudinally both after 100h creep test and stopped half the way of the test (40h and 60h) by immediate water quenching to fix the substructure in the tested specimens Materials Science Forum Online: 2005-01-15 ISSN: 1662-9752, Vols. 475-479, pp 2849-2852 doi:10.4028/www.scientific.net/MSF.475-479.2849 © 2005 Trans Tech Publications Ltd, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications Ltd, www.scientific.net. (Semanticscholar.org-11/03/20,13:01:30)

1 citations

Patent
29 Jun 2002
TL;DR: In this paper, a powder injection device in a spray casting equipment is provided to increase powder injection efficiency, improve powder distribution characteristics, increase reaction efficiency between molten metal and powder and simplify manufacturing process by directly injecting reinforcing powder into a high pressure gas supply pipe.
Abstract: PURPOSE: A powder injecting device in a spray casting equipment is provided to increase powder injection efficiency, improve powder distribution characteristics, increase reaction efficiency between molten metal and powder and simplify manufacturing process by directly injecting reinforcing powder into a high pressure gas supply pipe. CONSTITUTION: In a powder injection device which is connected to a spray casting equipment manufacturing an alloy plate by spraying molten metal onto a plate using a high pressure gas so as to inject reinforcing powder into a matrix when manufacturing a composite material by spray forming or a dispersion reinforced alloy, the powder injecting device in the spray casting equipment comprises a powder injection pipe(13) at the front of which a nozzle(12) inserted into a high pressure gas supply pipe(6) is formed, and the rear of which is connected to flow in a high pressure inert gas; a powder container(14) which is formed to store a certain amount of reinforcing powder and connected to a certain part of the upper part of the powder injection pipe(13); and a powder control unit(15) installed at the lower part of the powder container(14) to discharge a certain amount of powder into the powder injection pipe(13).

1 citations

01 Nov 1995
TL;DR: In this article, the effect of geometry and process parameters on spray pattern and particle size distribution is discussed, as well as the final spray formed deposit produced by these deposition systems, and the results of Alcoa's research and development work on three linear nozzle designs.
Abstract: Commercial production of aluminum sheet and plate by spray atomization and deposition is a potentially attractive manufacturing alternative to conventional ingot metallurgy/hot-milling, and to continuous casting processes because of reduced energy requirements and reduced cost. To realize the full potential of this technology the Aluminum Company of America (Alcoa), under a cooperative agreement with the U.S. Department of Energy, has investigated currently available state-of-the-art atomization devices to develop nozzle design concepts whose spray characteristics are tailored for continuous sheet production. This paper will discuss Alcoa`s research and development work on three linear nozzle designs. The effect of geometry and process parameters on spray pattern and particle size distribution will be presented. The discussion will focus on the final spray formed deposit produced by these deposition systems.

1 citations


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Metrics
No. of papers in the topic in previous years
YearPapers
202310
202216
202117
202037
201933
201826