开花的时间
Ceramic components manufacturing by lective lar sintering
Ph.Bertrand a ,F.Bayle a ,C.Combe a ,P.Goeuriot b ,I.Smurov a ,*
a
Ecole Nationale d’Inge
´nieurs de Saint-Etienne (ENISE),DIPI Laboratory,58rue Jean Parot,42023Saint-Etienne Cedex 2,France b
E ´cole Nationale Supe
´rieure des Mines de Saint-Etienne (ENSMSE),Centre SMS 158,Cours Fauriel,42023Saint-Etienne Cedex 2,France Available online 1September 2007
Abstract
In the prent paper,technology of lective lar sintering/melting is applied to manufacture net shaped objects from pure yttria–zirconia
powders.Experiments are carried out on Phenix Systems PM100machine with 50W fibre lar.Powd
er is spread by a roller over the surface of 100mm diameter alumina cylinder.Design of experiments is applied to identify influent process parameters (powder characteristics,powder layering and lar manufacturing strategy)to obtain high-quality ceramic components (density and micro-structure).
The influence of the yttria–zirconia particle size and morphology onto powder layering process is analyd.The influence of the powder layer thickness on lar sintering/melting is studied for different lar beam velocity V (V =1250–2000mm/s),defocalisation (À6to 12mm),distance between two neighbour melted lines (so-called ‘‘vectors’’)(20–40m m),vector length and temperature in the furnace.The powder bed density before lar sintering/melting also has significant influence on the manufactured samples density.
Different manufacturing strategies are applied and compared:(a)different lar beam scanning paths to fill the sliced surfaces of the manufactured object,(b)variation of vector length (c)different strategies of powder layering,(d)temperature in the furnace and (e)post heat treatment in conventional furnace.Performance and limitations of different strategies are analyd applying the following criteria:geometrical accuracy of the manufactured samples,porosity.The process stability is proved by fabrication of 1cm 3volume cube.#2007Elvier B.V .All rights rerved.
PACS :42.62.Àb;61.43.Gt;81.05.Je;81.20.Ev
Keywords:Ceramic powder;Stabilized zirconia–yttria;Selective lar sintering
1.Introduction
Lar-bad rapid manufacturing systems are becoming wide-spread in industries processing metallic materials.Recent progress in this field allows creating fully functional parts directly from metal powders without using any binders or post-processing but it has not so far reached ceramic materials applications [1].
Selective lar sintering/melting (SLS/M)of ceramic powders is less employed due mainly to low availability of machines appropriate for ceramics lar sintering or melting.Some of them are reported in [2,3].Ceramic components with simple geometries can be obtained by conventional compaction
of powder [4].For achieving more complex geometries,SLS/M process ems to be the most promising way.
Due to its good mechanical properties and its biocompat-ibility yttria–zirconia is the most ud ceramic in medical application.Conventional ways to process this material are not efficient.ZrO 2–Y
2O 3SLS studied in [5–7]was realized with additional ceramics powders mixed with zirconia powder to increa lar absorption.European standard CE 0476controlling compositions for medical u does not allow this mix.Such mixes have been applied mainly for building ceramic shell molds [8]and solid oxide fuel cells to benefit from their thermal resistance.
SLM process has a real potential for medical applications that often imply customized production with specific geometries.This requires new design possibilities and high accuracy in geometry.Scanning systems ever ud in medicine,can model parts.This model will be sliced and then manufactured.
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Available online at
Applied Surface Science 254(2007)989–992
*Corresponding author.Tel.:+33477910161;fax:+33477743497.E-mail address:smurov@eni.fr (I.Smurov).
0169-4332/$–e front matter #2007Elvier B.V .All rights rerved.doi:10.1016/j.apsusc.2007.08.0
85
The prent paper describes the way to process pure yttria–zirconia powder by SLS/M method.2.Powder characteristics
Five different types of pure yttria–zirconia powder were analyd to determine the influence of their characteristics on the process (Table 1).
The particle size is one of the most influencing factors in SLM process regarding powder.The particle size of the different analyd powder was varying from less than 1to 40m m.
1.064m m wavelength fiber lar radiation ud in the experiments is weakly absorbed by this material [9].In this regard,the experiments showed that the smallest particle size is required to obtain pure ZrO 2–Y 2O 3sintered layers.
The particle geometry has an influence on the roller powder spreading and on density.The more spherical the particles are,the better result is obtained.
Note that the particle size is directly linked with the layer thickness.
Different powders (atomized,non-atomized or crushed)have been compared.This factor has an influence upon the roller powder spreading as well.When the particles are not atomized some electrostatic charges trend to create agglom-erate particles.This results in scratches on the current layer,conquently the general quality decreas.
As the powder composition is defined by CE-standard,regarding the results obtained by spreading powder onto the 100mm alumina cylinder,one may conclude that the best powder for ZrO 2–Y 2O 3SLS/M process is the atomized one with a particle size distribution lower than one micrometer.The results shown further on in the paper have been obtained using Zircar ZYP30TM .3.Results and discussion
太极尺
3.1.Determination of the lar and machine parameters influence
Lar parameters have a great influence on the final product quality,but the way of powder spreading requires also attention.Each of the following points has been carefully taken into account:
(a)Orientation of the lar vector:lar vectors need to be oriented to avoid short vectors (who lengths is compar-able to their width)which result in droplets formation.
(b)Length of the lar vector:one may note that the lar is melting/sintering a ction of the CAD drawing.By this way,veral lar vectors have to fulfill this ction.This leads to a difference between vector lengths.This difference results in variable energy input per single vector and heat transfer variation within a layer.The delay between two adjacent vectors is t and kept constant to control the heat transfer in each layer.To calculate this delay one may u the following formula:D ¼
L max n
where D is the delay,L max is the length of longest vector and n is the lar beam velocity.
温柔可亲的反义词
(c)Powder layering strategy:the aim is to obtain a homo-geneous powder bed with the highest density and a stable layer thickness.The most important thing is to determine the appropriate layer thickness.This can be done by analysis of the lar beam penetration in the powder bed.
To obtain the cohesion of the manufactured layers lar needs to penetrate at least through the last powder layer and the previous one.To satisfy this requirement the layer thickness ud in this study was 30m m.It was shown that the particles need to be 10times smaller compared to the layer thickness for the efficient roller powder layering.The influence of the different motions of the roller on the layer surface homogeneity was studied.To increa the powder bed density the roller needs to c
ompress the powder bed.To meet this goal a customized powder layering quence has been created.
(d)Temperature in the enclosure:this temperature stimulates the sintering and/or melting process and helps to avoid cracks during solidification.The energy delivered to the powder bed by the furnace permits to increa the scanning velocity.Powder preheating before sintering reduces the apparition of micro cracks [7].On the other hand the temperature in the enclosure decreas the powder flowability and impairs the process repeatability.
马力和功率换算
(e)Post heat treatment in the conventional furnace:this post-treatment did not increa the density.Maximum furnate temperature was 12008C.The dark colour of the parts results from a lack of oxygen,above 2008C zirconia turned back into white.3.2.Obtained properties
The above discusd approach was applied to manufacture parts to study the geometry reproduction capability and to measure the density.
According to the process parameters discusd above,experiments were carried out to define their influence.Tests have been performed according to Table 2.
Accurate geometry 3D objects from pure zirconia were obtained using this SLS/M process (Figs.1and 2).The density remains low,only 56%(Fig.3).One may note that further sintering in conventional furnace cannot increa the object
Table 1
List of different powder ud for experimental test Origin Description
Particle size Baı¨kowski Yttria–zirconia (4mol%),atomid <40Â10À6m Baı¨kowski Yttria–zirconia (4mol%),crushed <10À6m Zircar ZYP30(10wt.%),atomid,Lot 32A <10À6m
Tioxide YZ5B,atomid
<40Â1100À6m ENSMSE
YZ3P (3mol%),atomid
<4010À6m
P .Bertrand et al./Applied Surface Science 254(2007)989–992
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Table2
Experimental tests
Bench Origin Parameters
Test Sample Defocalisation
(m)Lar vector
shift(m)
Lar beam
velocity(m/s)
Odd
layer(8)
Even稻城亚丁旅游
layer(8)
Lar vector
length(m)
Time shift between
two lar vectors(s)
121030Â10À6 1.750018010À20
5416Â10À330Â10À6 1.750018010À20
6426Â10À330Â10À6 2.00001802Â10À210Â10À3 7446Â10À340Â10À6 1.50001802Â10À213Â10À3 8466Â10À340Â10À6 2.00001802Â10À210Â10À3 261030Â10À6 1.75090À902Â10À211Â10À3 362030Â10À6 2.00090À9010À20 463040Â10À6 1.25090À9010À20
9856Â10À340Â10À6 1.75090À9010À20
10866Â10À340Â10À6 2.00090À9010À2
Fig.1.Pure zirconia3D objects manufactured by SLS/M technology(a:CAD design,b:real manufactured
part).
Fig.2.Accurate geometry performed by SLS/M technology using pure zirconia powder(a:part of a turbine blade,b:walls).
P.Bertrand et al./Applied Surface Science254(2007)989–992991
density.This states the fact that the lar melts partially the ceramics and consolidates the structure (Fig.4).
To improve the ZrO 2component density,one has to increa the powder bed density.The theoretical density of a powder bed compod of single-size particles is 74%.But when the particle sizes are lower than one micron and their shapes are not perfectly spherical some agglomerates appear that decreas the powder bed density.4.Conclusion
The density and the mechanical properties of the manu-factured samples do not correspond to their potential medical applications as dental bridges.However this study has demonstrated that processing pure yttria–zirconia powder by SLM facilities without additive element is possible.Analysis of
the influence of the powder characteristics,lar and SLM machine parameters on the ZrO 2–Y 2O 3component properties was carried out.Manufacturing powder with appropriate characteristics suitable for SLS process is another challenging task.
Acknowledgement
The authors thank the Region Rho
油条是怎么做的
ˆne-Alpes for its support within the project COCAGV2.References
[1]Wohlers Report,State of the Industry Annual Worldwide Progress Report,
ISBN 0-9754429-3-7,2007.
[2]A.Manthiram,H.L.Marcus,D.L.Bourell,Selective lar sintering using
nanocomposite materials,US Patent 5,431,967(1995).
[3]Device for the production of thin powder layers in particular at high
temperature,during a method involving the u of a lar on a material,Applicant PHENIX SYSTEMS,
Inventor Patrick Teulet,WO/2005/002764,PCT/FR2004/001646.
[4]J.Li,H.Liao,L.Hermansson,Sintering of partially-stabilized zirconia and
k开头的单词partially-stabilized zirconia-hydroxyapatite composites by hot isostatic pressing and pressureless sintering,Biomaterials 17(18)(1996)1787–1790.表演用英语怎么说
[5]Y .Tang,J.Y .H.Fuh,H.T.Loh,Y .S.Wong,L.Lub,Direct lar sintering of a
silica sand,Mater.Design 24(8)(2003)623–629.
[6]G.Casalino,L.A.C.De Filippis,A.D.Ludovico,L.Tricarico,An inves-tigation of rapid prototyping of sand casting molds by lective lar sintering,J.Lar Appl.14(2)(May 2002)100–106.
[7]J.Wilkes,K.Wisnbach,Rapid manufacturing of ceramic components for
medical and technical applications via lective lar melting,Conferences Euro-uRapid,Frankfurt,November 27–28,2006,pp.A4/1.
[8]T.H.Hsing,Y .H.Chuan,T.C.Chen,H.Y .Chen,C.C.Chang,C.H.Liu,
Development of rapid prototyping system for ceramic shell mold of precision casting,in:Proceedings of the IEEE International Conference on Mechatronics,2005,pp.483–486.
[9]P.Colomban,Imagerie Raman de mate
´riaux et dispositifs he ´te ´roge `nes,Techniques de l’inge
´nieur Spectrome ´trie Raman,
P2865.Fig.3.(a)Zirconia cube with 56%density;(b)top view of open
porosity.
Fig.4.The traces of zirconia melting that fixes the structure and does not allow
increasing the density by heating in a conventional furnace.
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