Ce travail cherche à étudier la microstructure, les propriétés mécaniques et tribologiques de deux types de WC-Co déposés sur un acier SAE 1045. Les caractérisations microstructurale et mécanique ont été menées pour relier la morphologie, la rugosité, la dureté, la ténacité à la rupture et les contraintes résiduelles aux performances tribologiques. Des essais d'indentation conventionnelle et instrumentée sont réalisés pour déterminer la dureté et le module d'élasticité. La diffraction X a été utilisée pour déterminer les contraintes résiduelles en surface et la technique du trou incrémentaI pour leur répartition dans l'épaisseur. Les résultats indiquent des contraintes résiduelles plutôt de compression à la surface et la technique du trou révèle que la répartition des contraintes n'est pas uniforme dans l'épaisseur. Le revêtement WC-10Co-4Cr a des contraintes résiduelles de compression alors que, dans le revêtement WC-12Co, elles sont de traction. Des essais d'érosion à sec ont été menés selon la norme ASTM G-76 et avec des angles d'attaque de 30 et 90°. Nous avons trouvé que le taux d'érosion est plus élevé lorsque l'angle d'impact est de 90°. Une combinaison des types d'usure, fragile et ductile, a été observée. Les résultats indiquent que pour le matériau massif de WC-Co, plus le libre parcours moyen d'agglomérat est faible plus le taux d'usure est faible. De plus, il a été déterminé que le revêtement WC-10Co-4Cr présente une résistance à l'usure élevée due à la faible quantité de phase fragile présente W2C et des valeurs de contraintes résiduelles de compression élevées comparativement au revêtement WC-12Co. / The present investigation is conducted to determine the microstructural, mechanical and tribological features of two different WC-Co systems deposited onto SAE 1045 steel. Microstructural and mechanical characterization was carried out in order to relate their morphology, roughness, hardness, fracture toughness and residual stresses to their tribological performance. Both conventional and instrumented indentation tests were also carried to measure hardness and elastic modulus. X-ray diffraction techniques were used to determine the surface residual stresses and the incremental hole drilling technique for their repartition through the thickness. The results indicate that both the bulk samples and the coatings exhibit compressive residual stresses on the surface and the hole-drilling technique indicates that the profile is not uniform. The WC-10Co-4Cr coatings displays compressive residual stresses, whereas the WC-12Co coating presents tensile residual stresses. Dry erosion tests according to the ASTM G-76 standard were carried out at 30° and 90° angle of impingement. The erosion rate for both coated systems was higher when the erosion test was carried out at an angle of 90°, and a combination between brittle and ductile wear type mechanisms was observed. The results also indicate that the bulk WC-Co materials with lower the mean free path of binder exhibited the lower mean rate erosion wear. Also, it was determined that the WC-10Co-4Cr coating presented a highest erosive wear resistance as consequence of both a smaller W2C brittle phase content and a higher through-thickness residual compressive stresses values, when compared to the WC-12Co coating.

Zugl.: Diss. phil.-nat. Bern, 1927.

Th. 3e cycle--Urban. et aménage.--Toulouse 2, 1987.

The island of Naxos, which lies in the central-southern Aegean Sea, is part of the Attic Cycladic Massif. This, a group of islands, containing metamorphic complexes polymetamorphosed during the Tertiary, forms an arcuate belt between mainland Greece and Turkey. The present-day tectonic setting of this area is one of convergence between Africa and Europe, via a subduction zone situated to the south of the Attic Cycladic Massif. The back-arc region of this subduction zone is undergoing present-day extension. This study investigates the nature of Barrovian metamorphism on Naxos, and its relationship to the timing of compressional and extensional tectonics in the Attic Cycladic Massif. The earliest Tertiary phase of metamorphism is a blueschist event of Eocene age (M1), which is variably overprinted by an Oligo-Miocene (M2) metamorphism of Barrovian character. The M2 event is most strongly developed on Naxos, where it resulted in upper amphibolite facies metamorphism and associated partial melting. The high grade core of the metamorphic complex is divided into a Lower Series of meta-pelites and meta-carbonates, and a structurally underlying core of leucogneisses. The syn- to post- M2 structural evolution of the metamorphic complex is interpreted as resulting from a continuum of northerly-directed non-coaxial deformation. The earliest structures (D<SUB>1</SUB>), occur as NNE-SSW trending meso- and macro-scale recumbent isoclinal folds, which deform a series of pre-M2 (Hercynian?) granitic gneisses in the leucogneiss core. The exhumation of the metamorphic complex is characterised by the development and re-working of non-coaxial protomylonitic fabrics formed under successively lower grade metamorphic conditions. This non-coaxial deformation, termed D<SUB>2</SUB>, is interpreted as having occurred during low-angle ductile extension of the metamorphic complex. During the latter stages of D<SUB>2</SUB> deformation, northwards-directed non-coaxial extension was accompanied by a component of W-E-directed sub-horizontal compression (D<SUB>3</SUB>), possibly related to large-scale rotation of the terminations of the originally rectilinear arc-system. The textural evolution of meta-pelite assemblages is related to divariant continuous equilibria in the simplified system KFMASH and to univariant equilibria in the system KTiFMASH, as appropriate for different bulk rock compositions. The mineral textures and inclusion relationships observed constrain the prograde M2 path as being one of heating and decompression, during which reaction products were continuously incorporated into the sub-horizontal composite foliation. Estimates of physical conditions during M2 metamorphism, made through garnet-biotite Fe-Mg geothermometry and the approach of internally consistent datasets, indicates (P, T,) conditions of ≈ (6-7±2 kbar, 560-660±50 deg. C) in the Lower Series, and ≈ (7-8±2 kbar, 640-690±50 deg. C) in the leucogneiss core. Geothermobarometry of zoned assemblages in meta-pelites from the leucogneiss core indicates a prograde P-T path of heating (60-100 deg. C) and decompression (1-3 kbar). (P, T) estimates and petrogenetic grids constrain equilibrium fluid compositions to be water-rich. Strontium isotopic studies suggest that anatexis in the leucogneiss core is not simply the result of large-scale partial melting of meta-pelites. Incipient anatexis on the margin of the leucogneiss core occurred by water-saturated melting of meta-pelites, whereas melting in the leucogneiss core occurred dominantly by re-melting of Models relating the exhumation of the metamorphic complex on Naxos to extensional shear zones of the type proposed for 'metamorphic core complexes' in the Basin and Range Province of North America are discussed. It is suggested that M2 ultrametamorphism on Naxos occurred in an island-arc setting, as the result of the emplacement of a basic intrusion below the present-day erosional surface. Ductile extension began before the M2 peak, possibly because of the southerly migration ('roll back') of the subduction zone to its present-day position.

No description available.

Inaug. _ Diss.: Philosophisch-Naturwissenschaftliche Fakultät: Basel: 1972. Tiré à part des "Basler Beiträge zur Geographie" n° 17, 1974. _ Résumé en français. _ Bibliogr. p. 140-145.

(Diss. Phil.-Naturwiss. Bern : 1964). / Sonderdruck aus: Eclogae geologicae Helvetiae. Vol. 57, Nr. 2, 1964.

Diss. Phil. Bern, 1908. / SA aus: Mitteilungen der Naturforschenden Gesellschaft in Bern. - (1911).

Diss. Phil.-nat. Zürich, 1966. / Beil.: Geological map of the Damavand-Firuzkuh-region (Central Elburz, Iran), 1:100'000 (Peter Allenbach und R. Steiger, 1965).

Zugl.: Diss. Bern, 1965. / Dissertationsausgabe als Sonderdruck erschienen.