APPLICATION OPPORTUNITIES OF DIFFERENT GLAZES TO

AL2O3 TECHNICAL CERAMICS

Nikoletta PUSKÁS

Dr. László A. GÖMZE

Ildikó LUKÁCS

University of Miskolc, Department of Ceramics and Silicate Engineering

microCAD 2005

Miskolc

10-11 March 2005

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Introduction

How develop the smoothness of the technical ceramics?

Experiments and investigations at the Department of Ceramics and Silicates Engineering

Using of porcelain and earthenware glazes

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Materials – Composition

4 sorts of glazes

1: earthenware glaze material

2, 3, 4: porcelain glaze materials

Wt % - 1 - - 2 - - 3 - - 4 -

Al2O3 13,99 14,49 13,22 7,32

SiO2 61,5 69,02 67,73 85,56

K2O 4,76 2,11 5 0,84

CaO 9,56 8,63 13,26 2,18

Fe2O3 3,88 3,03 3,8 2,58

ZnO 3,63 2,72 - -

Na2O 2,68 - - -

MgO - 2,72 - -

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Materials – Grain structures

1

3

2

4

Inhomogenity, grain size 0,5 – 30 m

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Materials – Technology

Densities of glaze suspensions: 1: 1450 g/l 2: 1250 g/l 3: 1350 g/l 4: 1275 g/l

Firing temperature: 1270 °C

Dipping

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Unusable results

Glazes marked 2, 3 and 4 did not develop perfect coatings

Glaze skips

Pinholes

Too thin coating

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Further examinations

Further examinations, using glaze material marked 1 in different densities: 1350 g/l 1450 g/l 1500 g/l

Different dry material content alumina substrates made by casting: Porous Medium Compact

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Testing methods – Microhardness measurement

Applied loading force: 2 N Time of loading: 10 sec

Medium compact bodies with different density of glazes

Different compact base ceramics with 1350 g/l density glaze

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Testing methods – Scratch test

Starting load: 10 N Final load: 100 N

Table speed: 10 mm/min Loading gradient: 10 N/mm

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Results – Microhardness

HVM values of middle compact samples glazed with different density glaze materials

619 617

600

580

590600

610

620

1350/m 1450/m 1500/m

signs of samples

HV

M

HVM values of different compact samples glazed with 1350 g/l density glaze material

621 619

601

590

600

610

620

630

1350/c 1350/m 1350/p

signs of samples

HV

M

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Results – Scratch test

Critical load values of middle compact samples glazed with different density

glaze materials

58

6259

545658606264

1350/m 1450/m 1500/m

Signs of samples

Cri

tic

al

loa

d

(N)

Critical load values of different compactness samples glazed with

1350 g/l density glaze material 79

6259

50556065707580

1350/c 1350/m 1350/pSigns of samples

Cri

tic

al

loa

d (

N)

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Results – Scratch test

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Results – Roughness

Roughness values of glaze coatings and base ceramics

00,5

11,5

22,5

Al2O3 PorcelainRa

rou

gh

nes

s va

lue

roughness of theglaze

roughness of thebase ceramic

roughness of theglaze

roughness of baseceramic

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Conclusions Nowadays glazing of technical ceramics exposed to heavy Nowadays glazing of technical ceramics exposed to heavy

duty use is a current and important challenge.duty use is a current and important challenge. The quality of the ceramic glazes strongly depends on the The quality of the ceramic glazes strongly depends on the

density of the glaze liquids and the geometrical shapes and density of the glaze liquids and the geometrical shapes and sizes of solid ceramic particles in the glaze slurries.sizes of solid ceramic particles in the glaze slurries.

Using the ceramic glazes we can considerably reduce the Using the ceramic glazes we can considerably reduce the roughness of the surfaces of the alumina technical ceramics, roughness of the surfaces of the alumina technical ceramics, increasing with this the estimated life cycles of these valuable increasing with this the estimated life cycles of these valuable technical items.technical items.

The scratch tests are necessary to reach the required hardness The scratch tests are necessary to reach the required hardness of the ceramic glazes and adhesive strength between the of the ceramic glazes and adhesive strength between the glazes and the alumina substrates.glazes and the alumina substrates.

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Department of Physical Department of Physical Metallurgy and MetalMetallurgy and Metalllforming forming

Department of Mechanical Department of Mechanical TechnologyTechnology

Acknowledgement

Many thanks for your attention!