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ENGINEERING CERAMICS FOR INDUSTRIAL APPLICATIONS;WEAR-, HEAT'- AND AU'TOMOTIVE TECHNOLOGY

A.Krauth, K. Berroth

Rosenthal Technik AGWerksgruppe IVIngenieurkeramik

D-8672 Selb

ABSTRACT

Material type, process technology and major propertiesfor four ceramic components mass produced during the lastthree years are described. Table A-1 defines the compo-nents, material type and fabrication method. fable A-2summarizes the density, bend strength, Weibull modulus andas fired dimensional tolerances. Production parts with flawsdetectable by lox visual examination are not included inthe tabulated data.

component material process technology

Bearings SiSiC dry pressing + siliconizing

Nozzles RBSN injection moulding + nitriding

Portliners ATI slip casting + gas firing

Cutlery Grips Al 20 3 extruding + gas firing

Table A-1: Component, Material and Process Technology

Major properties BearingsSiSiC

NozzlesRBSN

PortlinersATI

Cutlery gripsAl203

Density [g/cm z] 3.07 + 0.02 2.60 + 0.05 3.15 + 0.05 3.90 + 0.05

Bending strength [N/m mz] 380 + 30 220 + 20 30 + 5 370 + 30

Weibull modulus [m] 10 + 2 18 + 3 > 20 10 + 2

Tolerances (as fired) medium/ medium medium mediumDIN 7168 fine

Fable A-2: Major properties of selected components

Copyright © 1984 by ASME

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1. INTRODUCTION

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Modern fabrication technique for engineering cera-mics needs three important things - a triad of processspecification, process control specification and final checkspecification. The interdependence of process steps andprocess control will be shown in Fig. 1, which is the basisfor modern ceramic fabrication techniques. PLVOER Mlx CHECx INL SPRAY DRYING SILO VEILHIHL

6lanufactu ong Steps TO_P,00000 snd Fin I Q ,,,,1ro Assn ro e

- Chemical Analysis- X-Hap Diffmcrion

1 POWDER - Speci[ic Sur(are- Gre in Sic Distribution

2 POWDER PREPARATIONP rocess P isSrgaaicA ldit Bes

- ProPosPa3 MOULDING - Density

X- Rayingroscopy

-Process Parameters

4 BURNOUT - Dens 02X-Having

- Thermo-Halance

- Peaces Parameters5 MACHINING "GREEN" - Surface Condition

- (:heck of Dimensions

- process Parameters6 FINAL FIRING - Final Density

- X-Hay DiffractionX-Raying

- Mechanical PropertiesThermal Propedies

- C:lect meal Pr operties- Flaw Analysis, Rem Analysis

7 MACHINING "FINAI:' - Check of Dimer^+ioris- Component Testing

(Mechanical and Thermal)

Applicrr ionA COMPONENT - Testing

Design

Correlation hes aeen

manu[actuse^in Rn steps

lechnik

Fig. 1: Process steps and process control

This triad was and is the basis of the developmentof engineering ceramic components. Any development ofcomponents always includes use of production techniques,therefore reproductibility of the components at each stepof development is only as good as guaranteed by the pro-cess specifications and process control.

Since component properties and tolerances dependvery strongly on the fabrication process those special dataare given with respect to the components and the fabri-cation process_

2_ COMPONENTS, MATERIAL, F.ABRICACION PROPER'T'IESAND TOLERANCES

2.1 Slide Bearings From Siliconized Silicon Carbide

The production technology for seal rings and slidebearings which is described in Fig. 2 has two directions.

DRY PRESSING DRY PRESSING LO SHIRE

-.y F= .-^

MACHINING SILICONIZINC gin..<. ,

GRIN.— LAPPING CHECKING

Fig. 2 Fabrication technique for slide bearings components

For production quantities less than about five thou-sand parts dry pressing and automatic machining is used.Above five thousand parts, dry pressing to shape is themore economical solution.

Fig. 3: Slide bearing components - siliconized siliconcarbide

Fig. 3 shows some typical slide bearing componentsmade by dry pressing and automatic machining.

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These ceramic products can be produced with closeas fired tolerances and with little deviation in essentialproperties. 'Fable A-3 shows a survey of material proper-ties, tolerances and surface quality. These data have beenachieved in the mass production of more than one hundredthousand parts. Parts with detectable flaws have been iden-tified and eliminated.

The overall yield of this production line is between85 and 95 % and the production capacity is easy to ex-pand_ The production costs will depend on the numbers.

Density [g/cm'] 3.07 + 0-2

Bending strength [N/mml] 380 + 30

Weibull modulus 10 + 2

Modulus of Elasticity[N/mm'] 300 - 350 . 10 3

Thermal conductivity(W /rK] 150 at 20 °C

Thermal expansion [1/K] 4.4 . 10 -6

Tolerances as fired [DIN 7168] medium to fine

Surface quality as fired Ra = 4 µm + 1.0

grinded Ra = 0.35 pm + 0.1

lapped R= 0.OS pm + 0.005a

polished R= 0.03 pm + 0.005a

production yields [%J 85 - 95

'Fable A-3: Deviations of properties and tolerances formass produced seal rings and slide bearingsmaterial: siliconized silicon carbide

2.2 Welding And Oil Burner-Nozzles From ReactionBonded Silicon Nitride

The production technology (Fig. 4) used for nozzles,for welding (fig. 5) and for oil burners (Fig. 6) is injec-tion molding of silicon powder . This technology allowsmolding to shape with very little subsequent cleaning.Special shapes sometimes need to be finished by machining.This production technique is automated with a mechanizedremoval of the feed head.

T ElSILO ADO-IDS WE1CNING IWADING IND NIx ING

- f-- INJECTION HOULDING

RUIN OUT OF ADDITIVES ^\ -^-

NITF10[NG SILIC-ING FIRING

Gt+i Np ING ^^6ELLING

Fig. 4: Injection molding of nozzlesmaterial: reaction bonded silicon nitride

Fig. 5: RBSN welding nozzles(mass 5 g to 50 g)

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Fig. 6: RBSN oil-burner nozzles(mass 120 g)

The deviation in properties and tolerances through-out a production time of more than three years andhundred of thousand of parts is shown in Table A-4.

Density [g/cm'] 2.60 + 0.05

Bending strength [N/mm'] 220 + 20

Weibull Modulus 18 + 3

Modulus of elasticity [N/mmz] 170 - 190

Thermal conductivity [W/mK] 12 - 14

Thera al expansion [1/K] 3,0

Tolerances as fired [DIN 7168] medium

Surface quality as fired R = 1,0 - 3,0

production yields C%]a

96 - 98

fable A-4: Deviations of properties and tolerances formass produced welding and burner nozzlesmaterial: reaction bonded silicon nitride

This production technique can also be applied toother materials and components, too.

Components currently under development using in-jection molding at Rosenthal are:rotors for turbochargers and pumps, pistons, precom-bustion chambers for automotive use, cylinder heads forsmall motors and other components made from siliconnitride(RBSN, SSN), silicon carbide (SiSiC) and aluminium-titanate (API).

2.3 Ceramic Portliners From Aluminium Titanate

The production technology for ceramic portlinerswhich are used for the thermal insulation of automotivecylinder heads is a precision slip casting process whichhas been developed at Rosenthal in the last five years.Fig. 7 shows the manufacturing process for the plastermolds and the ceramic components.

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b

rr-® LH JGN

COPY MILLING

E PLASTER PLASTICS

DRYING TINE

SLIP CASTING [JYI/J]

REMOVE FROM M-D

FINAL MACHININGGREEN MILLING

FIRING

RASTER WORKING MOULD

Fig. 7: Slip casting process for the production of portlinermaterial: aluminium titanate

These ceramic portliners will be cast into aluminiumor iron cylinder heads. Therefore geometrical shape, ther-mal shock resistance, thermal conductivity and thermalexpansion have to meet close tolerances.

Fig. 8: Ceramic portliners in an air-cooled cylinder headmaterial: aluminium titanate

'Fable A-5 shows the achieved variations in proper-ties, tolerances and surface quality of the ceramic duct.

Density [g/cm'] 3.15 + 0.05

Bending strength [N/m mz] 30 + 5

Weibull modulus X20

Modulus of elasticity [N/mmz] 20

Thermal conductivity [W/mK] 1 - 2

"Thermal expansion [1/K] 0.5 - 1 . 10 -6

'Tolerances as fired [DIN 71681 medium

Variation of wall thickness [mm] + 0.2

surface quality of inside duct [R µm] 1,0

production yielda

1%7 75 - 85

Table A-5: Variation of properties and tolerances forseries of ceramic portlinersmaterial: aluminium titanate

New components of same material and same fabrica-tion technology are currently under development at Rosen-thal. The components are: insulation for exhaust manifolds,insulation for turbocharger housings and piston caps.

2.4 Cutlery Grips From Extruded Alumina

The last example is a consumer product but tolerancesand reproductibility have to be very close. The reason isthat the ceramic components has to be mechanically pre-stressed parallel to its length and this initially impressedstress reduces fracture and chipping when parts aredropped down or during action in the dish washer.

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L

Density [g/cm'] 3.90 + 0.05

Bending strength (glazed) [N/m mz] 370 + 30

Weibull modulus 12 + 2

Modulus of Elasticity [N/mmzJ 380

Thermal conductivity [W/mK] 30

Thermal expansion El/K] 7,8

Tolerances [DIN] medium

Surface quality [R pmja

as fired 1.0 - 2,0

glazed 0.06 + 0.02

yields [%] 60 - 80

SILO

SPRAY DRYING

AppI Tt VES vE ILN INL NNEAOINL ANO NI%INL

_ f

E%TRUDINL DRYING

SAVI L =^._. __J MILLING ^^'r.-L^ .Fable A-6: Cutlery grips extruded

material: alumina

BURN OV OF A001 IVES -- — – - —

NITRIOINL SILICONIZINL FIRINGP. SINIT. Iao CART BP ALTIT. NO AGO%.. 11RI

GRINDING CNEC%I NL

Fig. 9: Extrusion of cutlery gripsmaterial: alumina

Fig. 10: Cutlery grips produced by extrusionmaterial: alumina

Other components made from the same ceramicmaterials can be fabricated with this extrusion technology.These are: thereto couple shears, heat exchanger tubes,burner tubes, feeder tubes for liquid metal and other simi-lar shapes.

3. OUTLOOK

In order to give an outlook for future use of ceramiccomponents one has to say something about prices. Besidesthe problems concerning complexity of shapes, necessity ofgrinding and the dependence upon production volume, thereis one main rule which results from our experience in thelast 3 years: The prices of raw material used in our cera-mic mixtures range from 5 to 10 DM/kg (2 - 4 $/kg).Concerning high volume production one can say that theprice in 1983 for unground products is about 10 times theprice of the ceramic mix. We think that these prices canbe reduced furthermore with experience.

4. REFERENCES

1) H.R. Maier, H.Nink, A.Krauth

Statistische Festigkeitseigenschaften, Krafteinleitung andBauteilzuverlassigkeit am Beispiel von reaktionsgebunde-nem Siliciumnitrid

Ber. Dt.Keram. Ges. 54 (1977) Nr. 12, S. 413 - 416

2) Keramische Werkstoffe im Maschinenbau

Veroffentlichung in "Maschine + Werkzeug"Heft 2/83

3) Stefan R.Schindler, Axel Krauth

Beitrag der Keramik zur besseren Energienutzung

Vortrag anlalllich der DKG-Jahrestagung 1980 inWiesbaden

4) Dr.A.Krauth, Rosenthal Technik AG, Seib

Keramische Bauteile fur Otto- and Dieselmotoren

9. Statutsseminar "Kraftfahrzeuge and Stralenverkehr"des BMFT, 11. - 12.11.1981 in Bad Durkheim

Fig. 10 shows the ceramic components which areadjusted to the metal components by prestressing theceramic.

The deviation of properties and tolerances whichcan be achieved by extrusion technique are shown inTable A-6.

5) Le dispositif ceramique de vaporisation de Rosenthal

Veroffentlichung Oertli Journal No. 16, Oktober 1981

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