Submitted by Geyciane Santos (geyciane_thamires@hotmail.com) on 2015-10-26T14:33:03Z No. of bitstreams: 1 Dissertação - Astrid Siachoque Velandia.pdf: 17537751 bytes, checksum: 68db1c723dbe1e10240313c80e2e5ce9 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-10-26T17:54:01Z (GMT) No. of bitstreams: 1 Dissertação - Astrid Siachoque Velandia.pdf: 17537751 bytes, checksum: 68db1c723dbe1e10240313c80e2e5ce9 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-10-26T18:11:18Z (GMT) No. of bitstreams: 1 Dissertação - Astrid Siachoque Velandia.pdf: 17537751 bytes, checksum: 68db1c723dbe1e10240313c80e2e5ce9 (MD5) / Made available in DSpace on 2015-10-26T18:12:48Z (GMT). No. of bitstreams: 1 Dissertação - Astrid Siachoque Velandia.pdf: 17537751 bytes, checksum: 68db1c723dbe1e10240313c80e2e5ce9 (MD5) Previous issue date: 2015-08-10 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The albite granite is the latter facies of the A-type Madeira granite with alkaline affinity, which is a special Orosirian pulse of the A-type magmatic event in the Tapajós-Parima Province into Amazon craton. This facies is subdivided in two subfacies, the core albite granite and the border albite granite. The petrographic study allowed identify that the principals constituent minerals of the magmatic phase in these rocks undergone weak solid-state deformation, in which it is found locally feldspars with grain boundary migration, undulate extinction and mechanical twinning, as well as, some elongate crystals of quartz displaying typical chessboard pattern with slip planes preferably in the a-axes, dynamic recrystallization, subgrain rotation and inclusions of albite according to the limits of the crystals. These microstructures in granitic rocks indicate strain rates under intermediated to high temperatures. Geometric and kinematic analysis of the structures in the albite granite showed that: this granitic rock was deformed during a magmatic stage recording the S0 magmatic foliation, which was grouped in two orientations: N67°W/52°E e S79°W/58°N (predominant). The anisotropy of magnetic susceptibility and shape preferred orientation study, confirm the stability of the primary deformation in the albite granite, these results revealed predominantly subcoaxial magnetic and mineral fabrics in both subfácies. Subsequently, the albite granite was affected by brittle deformation through of transcurrent shear zones (ZCA-B) with plunges S70°W/56°N and S23°E/58°W respectively, and dominant dextral strike-slip component associated with the principal shear zone ZCA, as well as, normal faulting (FR) with prevailing attitude S60°E/58°S and normal-sense movement. The progressive petrological evolution and continue structural pattern of the albita granite facies with respect to earlier facies of Madeira granite, define that the emplacement in the upper crust of the different pulses in this granite, was result of nested pluton process controlled by NE-SW trending strike-slip system and predominantly dextral kinematics, which is an expression of regional deformation. / A fácies Albita granito é a fácies mais tardia do granito Madeira de afinidade alcalina a qual é um especial pulso do magmatismo tipo A que se desenvolveu de forma expressiva no período Orosiriano na província Tapajós-Parima no cráton Amazônico. Esta fácies se subdivide em duas subfácies: Albita granito de núcleo e Albita granito de borda. O estudo petrográfico permitiu identificar que os minerais constituintes da fase magmática destas rochas apresentam localmente feições de deformação plástica, cristais de K-feldspato e albita com limites lobados por migração de borda, extinção ondulante e geminação mecânica, assim como fenocristais de quartzo exibindo extinção ondulante em padrão de tabuleiro de xadrez com planos de deslizamento preferencialmente no eixo <a>, recristalização dinâmica, rotação de subgrãos e inclusões de albita e alinhadas segundo os limites dos cristais. Estas microestruturas em rochas graníticas indicam taxas de deformação sob temperaturas intermediárias. Análises geométrica e cinemática das estruturas levantadas em campo nas subfácies do Albita granito, comprovaram que localmente a rocha se deformou ainda num estágio magmático, registrando foliação magmática S0, agrupada em duas orientações: N67°W/52°E e S79°W/58°N (predominante). Os resultados do estudo de anisotropia de susceptibilidade magnética e orientação preferencial de forma avaliam localmente a estabilidade da petrotrama dúctil medida em afloramento e registram tramas magnética e mineral predominantemente subparalelas nas duas subfácies. Posteriormente, o Albita granito foi deformado rúptilmente por zonas de cisalhamento transcorrentes (ZCA-B) orientadas S70°W/56°N e S23°E/58°W, com cinemática dextral dominante associada ao cisalhamento principal ZCA, e por falhamento normal (FR) com atitude predominante S60°E/58°S, sob os efeitos de um campo regional de esforços que se manteve estável durante sua cristalização e deformação. A progressiva evolução petrológica e continuo padrão estrutural da fácies Albita granito com respeito às fácies mais precoces do granito Madeira refletem que o alojamento dos diferentes pulsos magmáticos deste granito na crosta superior, ocorreu associado com processos de nested plutons controlados por um contexto regional de deformação transcorrente com trend NE-SW e cinemática dextral predominante.

Dans le domaine du forgeage à chaud de pièces aéronautiques, les matrices en acier sont couramment rechargées, sur quelques millimètres d’épaisseur, par un alliage base cobalt (Stellite 21) déposé par procédé de soudage à l’arc (MIG). Dans le cadre de ce travail de thèse, ce rechargement « classique» est comparé à des rechargements Stellite 21 et Stellite 6 déposés par deux procédés émergents dans ce domaine, le PTA et le LASER. L’objectif est d’apporter des éléments de compréhension aux mécanismes d’endommagement de surface, notamment par écoulement plastique, de ces différents rechargements afin de dégager des voies d’amélioration pour augmenter la durée de vie des matrices. Pour cela, des essais tribologiques (semi-industriels et laboratoire) ont été mis en œuvre pour créer des endommagements de surface comparables à ceux observés sur matrices industrielles. Associées à ces essais, des investigations microstructurales, structurales et mécaniques multi-échelles ont été réalisées (traction, flexion, microdureté, MO, MEB, MEB-STEM, DRX, EBSD). Selon les couples « nuance/procédé » de rechargement, des mécanismes de déformation plastique par glissement des dislocations parfaites et par transformation de phase CFC en HC ont été identifiés. L’activation de ce dernier a pu être reliée à la température de transformation allotropique CFC/HC du cobalt. Cette température dépend à la fois (i) des éléments d’addition, variant en fonction de la nuance déposée (Cr, C,...), (ii) de la dilution (variation de la teneur en Fe) liée aux paramètres de soudage et (iii) du nombre de couches déposées. De plus, une influence significative de la transformation de phase sur l’évolution du coefficient de frottement a été mise en évidence. En effet, dans le cas où la transformation de phase n’est pas observée, le coefficient de frottement est stable durant l'essai alors qu'une chute de la courbe de coefficient de frottement a été reliée avec la transformation de phase CFC en HC. Parallèlement, l'écoulement plastique des dendrites est observé en extrême surface sur quelques dizaines de micromètre d'épaisseur dans la direction de glissement. Cet écoulement est associé à une forte texturation morphologique et cristallographique de la phase identifiée (CFC ou HC), avec une orientation des plans de plus grande densité atomique parallèlement à la surface de glissement. Les résultats montrent également que sous sollicitations tribologiques, un important durcissement est observé en surface (jusqu'à 90%) et une corrélation a pu être établie entre l'augmentation de la microdureté et le taux de déformation plastique. / In the field of hot forging of aeronautical parts, the steel dies are commonly hardfaced, on few millimeters thick, by a cobalt-based alloy (Stellite 21) deposited by arc welding (MIG). As part of this thesis, this "classic" hardfacing is compared to Stellite 21 and Stellite 6 hardfacings deposited by two emerging processes in this area, the PTA and the LASER one. The objective is to assess surface damage mechanisms, especially induced by plastic strain, of these various hardfacings. Tribological tests (laboratory and semi-industrial) were used to create surface damage comparable to those observed in industrial dies. Associated with these tests, multiscale microstructural, structural and mechanical investigations have been performed (tensile, bending, microhardness, OM, SEM, STEM, XRD, EBSD). According to the « material/process » couple, plastic strain mechanisms by perfect dislocation glide and by FCC to HCP phase transformation have been identified. The activation of the latter has been connected to the temperature of the allotropic phase transformation (FCC/HCP) in cobalt. This temperature depends on (i) the alloying elements, varying according to the deposited grade (Cr, C, ...), (ii) the dilution (Fe content evolution) connected to the welding parameters and (iii) the number of deposited layer. Moreover, a significant influence of the phase transformation on the evolution of the friction coefficient has been evidenced. Indeed, if the phase transformation is not observed, the friction coefficient is stable during the test, while a drop of the friction coefficient curve is connected with the FCC to HCP phase transformation. Moreover, the plastic flow of dendrites is observed at the extreme surface, on a few tens of micrometres in thickness, in the direction of sliding. It is associated with a high morphologic and crystallographic texturing of the identified phase (FCC or HCP), with the highest atomic density planes mostly oriented parallel to the sliding surface. The results also show that, under tribological laodings, a significant hardening is observed on the surface (up to 90%) and a correlation has been established between the increase in the microhardness and the plastic deformation ratio.