Flavio Neto - Academia.edu (original) (raw)

Papers by Flavio Neto

Research paper thumbnail of Titanium Powder on Surface Conditioning of Osseointegrable Surgical Implants Topographics Aspects

Materials Science Forum, 2006

Osseointegrable surgical implants are usually made on titanium or titanium alloys. The osseointeg... more Osseointegrable surgical implants are usually made on titanium or titanium alloys. The osseointegration process is improved by surface conditioning of these implants, increasing surface area with no loosing of bio-compatibility, i.e., without contamination by non bio-compatible materials. The surface conditioning of these implants might be accomplished in different ways: blasting, chemical etching, deposition, etc. Two alternatives considering titanium powders are discussed in this work: blasting and plasma spraying deposition. Results are presented in terms of topography of osseointegrable surgical implants through scanning electron microscopy techniques.

Research paper thumbnail of Nitrogen Bearing Austenitic Stainless Steels for Surgical Implants

Materials Science Forum, 1999

... The last effect increases the work hardening rate [10]. Page 3. ... Test pieces were withdraw... more ... The last effect increases the work hardening rate [10]. Page 3. ... Test pieces were withdrawn from the forged bars to perform tensile tests, potentiodynamic polarization tests and sensitization tests. The last tests were carried out according to Practice A of the ASTM 262 standard. ...

Research paper thumbnail of High Nitrogen Steels. Nitrogen Bearing Martensitic Stainless Steels: Microstructure and Properties

Isij International, 1996

ABSTRACT

Research paper thumbnail of Cracking of 2.25Cr–1.0Mo steel tube/stationary tube-sheet weldment of a heat-exchanger

Engineering Failure Analysis, 2008

The premature failure of a horizontal heat-exchanger, which occurred after service exposure at 58... more The premature failure of a horizontal heat-exchanger, which occurred after service exposure at 580°C for 50,000 h, revealed the occurrence of extensive through-thickness cracking in approximately 40% of the tube/stationary tube-sheet welds. Additionally, the internal surface of the welded joint featured intensive secondary intergranular cracking (up to 250 lm deep), preferential formation of a 150 lm thick layer of (Fe,Cr) 3 O 4 and internal intergranular oxidation (40 lm deep). The welded region also showed intense carbon pick-up and, as consequence, severe precipitation of intergranular M 7 C 3 and M 23 C 6 carbides. The fracture surface was composed of two distinct regions: a ''planar'' region of 250 lm, formed due to the stable crack growth along by the intergranular oxidation; and a slant region with radial marks, formed by the fast crack growth along the network of intergranular carbides. The association of intergranular oxidation pre-cracks with microstructural embrittlement promoted the premature failure, which took place by an overload mechanism, probably due to the jamming of the floating tube-sheet during the maintenance halt (cooling operation).

Research paper thumbnail of Effect of annealing on magnetic properties of Fe47.5%Ni alloy

Journal of Materials Engineering, 1989

The effect of annealing temperature on grain size, maximum permeability and coercive force of 47.... more The effect of annealing temperature on grain size, maximum permeability and coercive force of 47.5% nickel—iron alloys with different sulfur contents was investigated. Alloys with lower sulfur content require lower annealing temperature to attain specified values of magnetic properties. The experimental results show that the coefficient 3y/Ms, wherey is the domain wall energy andM s is the saturation magnetization, can be used to correlate both coercive force and maximum permeability to grain size.

Research paper thumbnail of Ti–Al–V powder metallurgy (PM) via the hydrogenation–dehydrogenation (HDH) process

Journal of Alloys and Compounds, 2003

The present investigation compares two routes for processing of sintered Ti-6Al-4V products via t... more The present investigation compares two routes for processing of sintered Ti-6Al-4V products via the hydrogenation-dehydrogenation (HDH) process: single and double step. DTA-TG of the titanium hydride powder indicated the occurrence of two endothermic reactions, one occurring around 375 8C and the other around 523 8C. The first transition might be related to the beginning of the hydride decomposition, the (d-TiH / Tib1d-TiH ) transus, while the second transition might be related to the final hydride decomposition, given 2 2 by (d-TiH 1Tib /Tib) transus. The microstructure of the sintered samples produced by both routes consist of a platelets and an 2 interplatelet b phase. The morphology of the b phase seems less continuous for the sample sintered from dehydrogenated powder, while the microstructure of the sintered sample obtained from hydrogenated powders showed lower volumetric fraction of pores. 

Research paper thumbnail of Titanium Powder on Surface Conditioning of Osseointegrable Surgical Implants Topographics Aspects

Materials Science Forum, 2006

Osseointegrable surgical implants are usually made on titanium or titanium alloys. The osseointeg... more Osseointegrable surgical implants are usually made on titanium or titanium alloys. The osseointegration process is improved by surface conditioning of these implants, increasing surface area with no loosing of bio-compatibility, i.e., without contamination by non bio-compatible materials. The surface conditioning of these implants might be accomplished in different ways: blasting, chemical etching, deposition, etc. Two alternatives considering titanium powders are discussed in this work: blasting and plasma spraying deposition. Results are presented in terms of topography of osseointegrable surgical implants through scanning electron microscopy techniques.

Research paper thumbnail of Nitrogen Bearing Austenitic Stainless Steels for Surgical Implants

Materials Science Forum, 1999

... The last effect increases the work hardening rate [10]. Page 3. ... Test pieces were withdraw... more ... The last effect increases the work hardening rate [10]. Page 3. ... Test pieces were withdrawn from the forged bars to perform tensile tests, potentiodynamic polarization tests and sensitization tests. The last tests were carried out according to Practice A of the ASTM 262 standard. ...

Research paper thumbnail of High Nitrogen Steels. Nitrogen Bearing Martensitic Stainless Steels: Microstructure and Properties

Isij International, 1996

ABSTRACT

Research paper thumbnail of Cracking of 2.25Cr–1.0Mo steel tube/stationary tube-sheet weldment of a heat-exchanger

Engineering Failure Analysis, 2008

The premature failure of a horizontal heat-exchanger, which occurred after service exposure at 58... more The premature failure of a horizontal heat-exchanger, which occurred after service exposure at 580°C for 50,000 h, revealed the occurrence of extensive through-thickness cracking in approximately 40% of the tube/stationary tube-sheet welds. Additionally, the internal surface of the welded joint featured intensive secondary intergranular cracking (up to 250 lm deep), preferential formation of a 150 lm thick layer of (Fe,Cr) 3 O 4 and internal intergranular oxidation (40 lm deep). The welded region also showed intense carbon pick-up and, as consequence, severe precipitation of intergranular M 7 C 3 and M 23 C 6 carbides. The fracture surface was composed of two distinct regions: a ''planar'' region of 250 lm, formed due to the stable crack growth along by the intergranular oxidation; and a slant region with radial marks, formed by the fast crack growth along the network of intergranular carbides. The association of intergranular oxidation pre-cracks with microstructural embrittlement promoted the premature failure, which took place by an overload mechanism, probably due to the jamming of the floating tube-sheet during the maintenance halt (cooling operation).

Research paper thumbnail of Effect of annealing on magnetic properties of Fe47.5%Ni alloy

Journal of Materials Engineering, 1989

The effect of annealing temperature on grain size, maximum permeability and coercive force of 47.... more The effect of annealing temperature on grain size, maximum permeability and coercive force of 47.5% nickel—iron alloys with different sulfur contents was investigated. Alloys with lower sulfur content require lower annealing temperature to attain specified values of magnetic properties. The experimental results show that the coefficient 3y/Ms, wherey is the domain wall energy andM s is the saturation magnetization, can be used to correlate both coercive force and maximum permeability to grain size.

Research paper thumbnail of Ti–Al–V powder metallurgy (PM) via the hydrogenation–dehydrogenation (HDH) process

Journal of Alloys and Compounds, 2003

The present investigation compares two routes for processing of sintered Ti-6Al-4V products via t... more The present investigation compares two routes for processing of sintered Ti-6Al-4V products via the hydrogenation-dehydrogenation (HDH) process: single and double step. DTA-TG of the titanium hydride powder indicated the occurrence of two endothermic reactions, one occurring around 375 8C and the other around 523 8C. The first transition might be related to the beginning of the hydride decomposition, the (d-TiH / Tib1d-TiH ) transus, while the second transition might be related to the final hydride decomposition, given 2 2 by (d-TiH 1Tib /Tib) transus. The microstructure of the sintered samples produced by both routes consist of a platelets and an 2 interplatelet b phase. The morphology of the b phase seems less continuous for the sample sintered from dehydrogenated powder, while the microstructure of the sintered sample obtained from hydrogenated powders showed lower volumetric fraction of pores. 