Notice bibliographique
Résumé
Wear causes loss of materials of moving parts and tools used in many fields. Wear can be reduced by employing appropriate materials and coatings, which requires an understanding of their microstructure, properties and tribological behavior. One of the high wear resistant materials is the Fe-Cr-B-based alloy system. Fe-Cr-B-based alloys have been fabricated using thermal spray, welding and sintering processes; and it has been found that their microstructure, properties and tribological performance vary from process to process. This dissertation focuses on advances made by employing recent processes to fabricate these alloys. The primary aim of this research is to understand the microstructure and tribology of the Fe-Cr-B-based alloys fabricated by the controlled short-circuit metal inert gas (CSC-MIG) welding and spark plasmasintering (SPS) processes.CSC-MIG was used to weld a Fe-28.2Cr-3.8B-1.5Si-1.5Mn (wt.%) cored wire alloy onto 1020 carbon steel substrate. SPS was employed to consolidate a Fe-45Cr-5.9B-2Si-0.1C (wt.%) gas-atomized powder alloy. Solidication behaviors of the gas-atomized powder and weldments were investigated through thermodynamiccalculations. Microstructure characterizations, hardness measurements and tribology testings were performed for these fabricated alloys.Upon cooling, the primary (Cr,Fe)2B phase began to form, followed by eutectic formation of the (Cr,Fe)2B and body-centered cubic (BCC) Fe-based solid solution phases. Because the powder contained a small amount of C, (Cr,Fe)7C3 was precipitated at the end of the solidication. The CSC-MIG weldment was composed of 44 wt.% primary and secondary orthorhombic (Cr,Fe)2B plates embedded in 56 wt.% BCC Fe-based solid solution, containing Fe, Cr, Mn and Si. The SPS specimen contained 65 wt.% (Cr,Fe)2B plates and 1 wt.% (Cr,Fe)7C3 precipitates dispersed in 34 wt.% BCC Fe-based solid solution, containing Fe, Cr and Si. The (Cr,Fe)2B phase was bigger in the weldment than the sintered specimen. The hardness of (Cr,Fe)2B was 24 GPa, independent of the alloy's composition and process parameters. As the B content increased, the fraction of (Cr,Fe)2B increased. As the (Cr,Fe)2B fraction increased, the bulk hardness of the specimens increased linearly. When the specimen's hardness and (Cr,Fe)2B size increased, abrasive wear resistance increased, while sliding wear resistance was independent of hardness but improved as the (Cr,Fe)2B size increased. The abrasive wear mechanism was microcutting, while sliding wear mechanisms were adhesion and mild oxidation.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».