The first stages of growth of wear-resistant coatings on cemented carbides

The first stages of growth of wear-resistant coatings on cemented carbides

Abstructsof fie Scandinavian Societyfor ElectronMicroscopy ELECTRON MIllROSCOPYOF ZEOLXTES P. Skjerpe, M. St#cker* and K. P, Lillerud** Department of...

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Abstructsof fie Scandinavian Societyfor ElectronMicroscopy

ELECTRON MIllROSCOPYOF ZEOLXTES P. Skjerpe, M. St#cker* and K. P, Lillerud** Department of Physics, Univessity Osln, *Center for Industrial HeSearchr Oslo; **Department Of Chemistry, UniversFty of Oslo

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ZeeoLites have considerable interest within the field of catalysis* In order to characterize tctlese catalysts, TEM is necessary to describe the microstructure and crystal defects on a fine SNX3le. In the present work, the zeolita erionite (hexagonal a=l3,2a and o==l4.8#) was studied. fn order to obtain stable specimens for TEN work" erionite samples were dealuminized four times and finally the powder was dispersed on holey carlbon films. Additional stabilization was attempted by keeping the specimen in vat=uum prior to TEN observation, Erionite crystals were often plate-shaped and selected area diffraction showed their c/a ratio to be somewhat different compared to the ideal structure, Streaking effects parallel to the c-axis were cummonly observed, indicating the presence af faults on IOOOl1, HREM observation and recording at 100,000 )Iwas possible before disintegration of the structural framework took place. Izages were recorded mainly in the [lOlO] projection. Image simulations for HRlEMwere carried out using the multlslice method,

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Al203 and TiN on, since they are not affected by the high temperature. Cemented carbides are used for wear parts and for metal cutting applications and by applying a thin layer (510 urn)of the above mentioned coatings, the wear resistance can be increased further. In the present work very thin combined Tic-Al203 coatings have been produced using the conventional CVD hot wall deposition technique. The aim was to examine the coatings concerning the morphol.ogyand composition and to study the nucleation and growth. The main method for the microanalysis has been AEM. For the analysis very sharp needle-shaped specimens have been used. They are very suitable for studies of the early growth stages of the coatings since they can be used directly after deposition without any further specimen preparation. Composition depth profiles &tsine3 by EDS are presented and also compared with results from atom probe analyses from the same specimens. Different types of abnormal growth of coatings is also presented. Coated cutting tool inserts have been examined by scanning Auger microscopy (S,AMj . These inserts were also used for preparing thin foils for AEM* Two different specimen preparation techniques were used. One was by electropolishing the specimen until the ooating was detached from the substrate and the other was by using a dimpler and ion-beam thinning*

THE FIRST STAGES OF GROWTH QF WEAR-RESISTANT COATINGS ON CEMENTED CARBfDES

ELECTRON DIFFRACTION PATTERNS FROM THIN AMORPHOUS FILMS OF SnO2

J, Skogsmo and H. Norden

E. S&br#den

Department University Gtjteborgc

of Physics, Chalmers of Technology, S-412 Sweden

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Chemical vapour deposition (CVD) is a method by which a thin uniform coating can be applied with a very good adherence on many different types of substrates. The deposition is usually pernlrrrr-cL1 -1 formed at reduced press*ureand Ts.&GVQ~CL temperature, around 1000°Cr which puts some requirements on the substrates, Tool steels, for example, are not SO well suited since they have to be quenched after coating, which is rather complicated and easily causes the coating to crack and peel off. Cemented carbide of the WC-Co type is perfect to deposit coatings of Tic,

and J. Taft4*

Department of Physics, Universsty Oslo 3, Narway; OSLO, Blindern, *Norsk Hydro Research Ce~tre~ 3901 Porsgrunn, Narway

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Electron diffraction offers several advantages in structure studies Of 2%'nOrphous films. Often only thin films, of 1 pm or less, are available, which may n.rrrl..Atn GJIc*.AUL*P=

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techniques. High precision in determination of interatomic distances will be possible if the high s = d?rsinB/XValues can he exploited: In an electron microscope operating at 2OQ kV s 2 40 8-l at the maximum diffraction angle Of 9' (JEM 2OOOFX). On the other hand multiple scattering may complicate the interpretation if quantitative comparison of