Aloisio Nelmo Klein - Academia.edu (original) (raw)
Ph.D. and researcher in Materials Science and Engineering. Focus on the development of new materials produced from powder (powder metallurgy, ceramics, and sintered composites) and its performance an applications
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Papers by Aloisio Nelmo Klein
Journal of The Brazilian Society of Mechanical Sciences and Engineering, Jun 1, 2008
Materials Research-ibero-american Journal of Materials, Apr 1, 2015
Materials Research-ibero-american Journal of Materials, Mar 1, 2007
Materials Research-ibero-american Journal of Materials, Jan 28, 2013
Materials Research-ibero-american Journal of Materials, May 20, 2014
Revista brasileira de aplicações de vácuo, Sep 24, 2010
Metals
In situ composite manufacture is an approach to improve interfacial adhesion between matrix and r... more In situ composite manufacture is an approach to improve interfacial adhesion between matrix and reinforcements, in which reinforcements are synthesized along composite processing itself. In situ powder metallurgy route, in particular, offers alternatives to some shortcomings found in other techniques. This work aims not only to review the state of the art on metal matrix composites (MMCs)—including cermets—obtained in situ by powder metallurgy, but also to dissect key aspects related to the development of such materials in order to establish theoretical criteria for decision making before and along experiments. Aspects regarding the design, raw material selection, and processing of such composites were observed and divided between concept, intrinsic, and extrinsic parameters. That way, by means of material databases and computational thermodynamics applied to examples of the reviewed literature, we aim at providing tools in both conducting leaner experiments and richer discussion in...
Frontiers in Mechanical Engineering
Sintered self-lubricating components may present inappropriate mechanical properties despite thei... more Sintered self-lubricating components may present inappropriate mechanical properties despite their excellent tribological properties. In general, alloying elements are used to improve these properties, but with a cost increase. As an alternative, surface enrichment (or surface alloying) with alloying elements may be applied. This study developed and characterized sintered composite materials surface-enriched with nickel or molybdenum. The results showed that the surface enrichment process is useful for increasing the tribomechanical properties. The Mo-enriched samples presented superior tribological results. Compared with the reference samples (not enriched), the Mo-enriched specimens showed an increase of 4,954% in scuffing resistance, lower friction coefficient (0.09), and reduced wear rate (68% and 96% lower for the specimen and the counter body). These results were mainly attributed to microstructural modification.
WIT transactions on engineering sciences, 1970
The Response Surface Method is an effective means of addressing the combined effect of plasma nit... more The Response Surface Method is an effective means of addressing the combined effect of plasma nitriding parameters on the corrosion resistance of materials. In this work, sintered steel was nitrided under different atmospheres: 75%N: 25%H2, and 25%N: 75%Hi. In addition, a series of samples was also nitrocarburized by adding CH4 to the nitrogen-enriched atmosphere. The thickness and composition of the resulting compound layers were determined, along with the resulting microhardness profiles. Finally, the corrosion resistance of the plasma-treated materials was evaluated by potentiodynamic polarization technique. The results indicated that the addition of CH^ to the plasma atmosphere increased the hardening depth and improved the corrosion rate of the resulting material.
Materials, 2019
Powder metallurgy is a competitive technology to produce ferrous near net shape parts for diverse... more Powder metallurgy is a competitive technology to produce ferrous near net shape parts for diverse engineering applications. However, their inherent porosity increases the susceptibility to oxidation and sealing their surface is mandatory to avoid premature degradation. Alongside, polymer derived ceramics (PDCs), such as silicon-carbonitride, have drawn attention concerning their high temperature and chemical stability. However, PDCs undergo volume shrinkage during ceramization that leads to defect formation. The shrinkage can be compensated by the addition of fillers, which are also capable of tailoring the ceramic resulting properties. This work evaluates the processing of PDC-based coatings loaded with ZrO2 and glass fillers to compensate for the shrinkage, densify the coating and seal the sintered steel surface. Therefore, polymeric slurries were sprayed onto sintered steel substrates, which were pyrolyzed at different temperatures for microstructural and oxidation resistance eva...
ABM Proceedings, Oct 1, 2018
Journal of The Brazilian Society of Mechanical Sciences and Engineering, Jun 1, 2008
Materials Research-ibero-american Journal of Materials, Apr 1, 2015
Materials Research-ibero-american Journal of Materials, Mar 1, 2007
Materials Research-ibero-american Journal of Materials, Jan 28, 2013
Materials Research-ibero-american Journal of Materials, May 20, 2014
Revista brasileira de aplicações de vácuo, Sep 24, 2010
Metals
In situ composite manufacture is an approach to improve interfacial adhesion between matrix and r... more In situ composite manufacture is an approach to improve interfacial adhesion between matrix and reinforcements, in which reinforcements are synthesized along composite processing itself. In situ powder metallurgy route, in particular, offers alternatives to some shortcomings found in other techniques. This work aims not only to review the state of the art on metal matrix composites (MMCs)—including cermets—obtained in situ by powder metallurgy, but also to dissect key aspects related to the development of such materials in order to establish theoretical criteria for decision making before and along experiments. Aspects regarding the design, raw material selection, and processing of such composites were observed and divided between concept, intrinsic, and extrinsic parameters. That way, by means of material databases and computational thermodynamics applied to examples of the reviewed literature, we aim at providing tools in both conducting leaner experiments and richer discussion in...
Frontiers in Mechanical Engineering
Sintered self-lubricating components may present inappropriate mechanical properties despite thei... more Sintered self-lubricating components may present inappropriate mechanical properties despite their excellent tribological properties. In general, alloying elements are used to improve these properties, but with a cost increase. As an alternative, surface enrichment (or surface alloying) with alloying elements may be applied. This study developed and characterized sintered composite materials surface-enriched with nickel or molybdenum. The results showed that the surface enrichment process is useful for increasing the tribomechanical properties. The Mo-enriched samples presented superior tribological results. Compared with the reference samples (not enriched), the Mo-enriched specimens showed an increase of 4,954% in scuffing resistance, lower friction coefficient (0.09), and reduced wear rate (68% and 96% lower for the specimen and the counter body). These results were mainly attributed to microstructural modification.
WIT transactions on engineering sciences, 1970
The Response Surface Method is an effective means of addressing the combined effect of plasma nit... more The Response Surface Method is an effective means of addressing the combined effect of plasma nitriding parameters on the corrosion resistance of materials. In this work, sintered steel was nitrided under different atmospheres: 75%N: 25%H2, and 25%N: 75%Hi. In addition, a series of samples was also nitrocarburized by adding CH4 to the nitrogen-enriched atmosphere. The thickness and composition of the resulting compound layers were determined, along with the resulting microhardness profiles. Finally, the corrosion resistance of the plasma-treated materials was evaluated by potentiodynamic polarization technique. The results indicated that the addition of CH^ to the plasma atmosphere increased the hardening depth and improved the corrosion rate of the resulting material.
Materials, 2019
Powder metallurgy is a competitive technology to produce ferrous near net shape parts for diverse... more Powder metallurgy is a competitive technology to produce ferrous near net shape parts for diverse engineering applications. However, their inherent porosity increases the susceptibility to oxidation and sealing their surface is mandatory to avoid premature degradation. Alongside, polymer derived ceramics (PDCs), such as silicon-carbonitride, have drawn attention concerning their high temperature and chemical stability. However, PDCs undergo volume shrinkage during ceramization that leads to defect formation. The shrinkage can be compensated by the addition of fillers, which are also capable of tailoring the ceramic resulting properties. This work evaluates the processing of PDC-based coatings loaded with ZrO2 and glass fillers to compensate for the shrinkage, densify the coating and seal the sintered steel surface. Therefore, polymeric slurries were sprayed onto sintered steel substrates, which were pyrolyzed at different temperatures for microstructural and oxidation resistance eva...
ABM Proceedings, Oct 1, 2018