The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform
Andre Paulo Tschiptschin - One of the best experts on this subject based on the ideXlab platform.
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microabrasion of three experimental cobalt Chromium Alloys wear rates and wear mechanisms
Wear, 2017Co-Authors: Flavio Parreiras Marques, Antonio Cesar Bozzi, Cherlio Scandian, Andre Paulo TschiptschinAbstract:Abstract Cobalt-Chromium Alloys are known for their excellent wear resistance. Many studies on the wear behavior of these Alloys were reported in literature. Nevertheless, microabrasive wear still lacks extensively investigation. Microabrasive wear behavior, of three experimental cobalt Alloys, was investigated: Alloy 1 similar to Stellite 250, 48 wt% Co, 29 wt% Cr, 19 wt% Fe; Alloy 2 similar to Stellite 6, 64 wt% Co, 24 wt% Cr, 4.2 wt% W, 2,3 wt% and Alloy 3 similar to Tribaloy – T400, 56 wt% Co, 8.5 wt% Cr, 29 wt% Mo, 3.3 wt% Si. These Alloys are being used for manufacturing guides for hot rolling seamless steel pipes. Alloy 2 and Alloy 3 are being tested as wear segments used inside a 2nd generation ethanol reactor. Tests were performed using three 0.1 g/cm 3 slurries composed by SiO 2 , Al 2 O 3 , and SiC particles, in a distilled water suspension. A load of 0.3 N was applied, the rotational speed was 20 rpm and the total sliding distance 48 m. Analysis of the Alloys' tribosurfaces – by Optical Microscopy, Scanning Electron Microscopy and Contact Stylus Profilometry – showed abrasive size, shape and hardness may influence wear coefficients significantly. Tests performed with SiC and Al 2 O 3 slurries resulted in greater wear rates than those with SiO 2 slurry. Alloy 1 showed the greatest wear coefficient, in comparison with the other two experimental Alloys, due to the absence of hard second phase precipitates in its microstructure. The variation of the wear coefficients as a function of abrasive hardness (H a ) and the compound alloy hardness (H s ) showed a linear correlation (R 2 = 0.73). Two-body abrasion (grooving wear) was the dominant wear micro-mechanism observed for all tests. Alloy 2, containing Laves phase showed a transition from ductile to brittle wear mechanism when tested with alumina slurries. The SiC slurry gave the highest worn volume among the three tested slurries.
Oscar Figuerasalvarez - One of the best experts on this subject based on the ideXlab platform.
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adhesion of dental porcelain to cast milled and laser sintered cobalt Chromium Alloys shear bond strength and sensitivity to thermocycling
Journal of Prosthetic Dentistry, 2014Co-Authors: Josep Serraprat, Jordi Canobatalla, Josep Cabratosatermes, Oscar FiguerasalvarezAbstract:Statement of problem New technologies have led to the introduction of new materials, so an evaluation of the adhesion of ceramics to these materials is needed. Purpose The purpose of this study was to compare the shear bond strength of dental porcelain to cast, milled, and laser-sintered cobalt-Chromium Alloys, and to investigate the adhesive bond and failure type after thermocycling, 90 metal cylinders (10 mm diameter and 10 mm height) were prepared from cast (30 specimens), milled (30 specimens), and laser-sintered (30 specimens) Alloys. Material and methods Ceramic cylinders (2.5 mm diameter and 4 mm length) were fused to the alloy cylinders. For each group, 15 specimens were thermocycled 5500 times at temperatures between 4°C and 60°C before testing. After testing, the specimen surfaces were visually examined to determine the failure mode. Differences in adhesion values according to manufacturing method, testing condition (thermocycling or no thermocycling), and interaction between the factors were evaluated with a 2-way ANOVA. The χ 2 test (95% confidence level) was performed to determine whether the failure mode was associated with the testing condition. Results Adhesion strengths for the nonthermocycled specimens were 42.79 ±14.14 MPa (cast), 37.56 ±9.18 MPa (milled), and 29.09 ±6.95 MPa (laser-sintered), and, for the thermocycled specimens, 16.52 ±8.96 MPa (cast), 22.21 ±13.25 MPa (milled), and 24.28 ±10.13 MPa (laser-sintered). Two-way ANOVA results indicated no statistically significant differences in adhesion among the manufacturing methods ( P =.257), but statistically significant differences were observed according to both testing conditions ( P P =.015). The χ 2 test indicated that the failure mode was not associated with the testing condition (thermocycled, P =.280; nonthermocycled, P =.240). Conclusions The porcelain adhesion values for all the materials were adequate for clinical applications. No significant adhesion differences were observed between cast, milled, and laser-sintered specimens, or among thermocycled and nonthermocycled laser-sintered specimens. However, significant adhesion differences were observed among the thermocycled and nonthermocycled cast and the milled specimens.
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adhesion of dental porcelain to cast milled and laser sintered cobalt Chromium Alloys shear bond strength and sensitivity to thermocycling
Journal of Prosthetic Dentistry, 2014Co-Authors: Josep Serraprat, Jordi Canobatalla, Josep Cabratosatermes, Oscar FiguerasalvarezAbstract:STATEMENT OF PROBLEM: New technologies have led to the introduction of new materials, so an evaluation of the adhesion of ceramics to these materials is needed. PURPOSE: The purpose of this study was to compare the shear bond strength of dental porcelain to cast, milled, and laser-sintered cobalt-Chromium Alloys, and to investigate the adhesive bond and failure type after thermocycling, 90 metal cylinders (10 mm diameter and 10 mm height) were prepared from cast (30 specimens), milled (30 specimens), and laser-sintered (30 specimens) Alloys. MATERIAL AND METHODS: Ceramic cylinders (2.5 mm diameter and 4 mm length) were fused to the alloy cylinders. For each group, 15 specimens were thermocycled 5500 times at temperatures between 4°C and 60°C before testing. After testing, the specimen surfaces were visually examined to determine the failure mode. Differences in adhesion values according to manufacturing method, testing condition (thermocycling or no thermocycling), and interaction between the factors were evaluated with a 2-way ANOVA. The χ(2) test (95% confidence level) was performed to determine whether the failure mode was associated with the testing condition. RESULTS: Adhesion strengths for the nonthermocycled specimens were 42.79 ±14.14 MPa (cast), 37.56 ±9.18 MPa (milled), and 29.09 ±6.95 MPa (laser-sintered), and, for the thermocycled specimens, 16.52 ±8.96 MPa (cast), 22.21 ±13.25 MPa (milled), and 24.28 ±10.13 MPa (laser-sintered). Two-way ANOVA results indicated no statistically significant differences in adhesion among the manufacturing methods (P=.257), but statistically significant differences were observed according to both testing conditions (P<.001) and interaction between the factors (P=.015). The χ(2) test indicated that the failure mode was not associated with the testing condition (thermocycled, P=.280; nonthermocycled, P=.240). CONCLUSIONS: The porcelain adhesion values for all the materials were adequate for clinical applications. No significant adhesion differences were observed between cast, milled, and laser-sintered specimens, or among thermocycled and nonthermocycled laser-sintered specimens. However, significant adhesion differences were observed among the thermocycled and nonthermocycled cast and the milled specimens.
Flavio Parreiras Marques - One of the best experts on this subject based on the ideXlab platform.
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microabrasion of three experimental cobalt Chromium Alloys wear rates and wear mechanisms
Wear, 2017Co-Authors: Flavio Parreiras Marques, Antonio Cesar Bozzi, Cherlio Scandian, Andre Paulo TschiptschinAbstract:Abstract Cobalt-Chromium Alloys are known for their excellent wear resistance. Many studies on the wear behavior of these Alloys were reported in literature. Nevertheless, microabrasive wear still lacks extensively investigation. Microabrasive wear behavior, of three experimental cobalt Alloys, was investigated: Alloy 1 similar to Stellite 250, 48 wt% Co, 29 wt% Cr, 19 wt% Fe; Alloy 2 similar to Stellite 6, 64 wt% Co, 24 wt% Cr, 4.2 wt% W, 2,3 wt% and Alloy 3 similar to Tribaloy – T400, 56 wt% Co, 8.5 wt% Cr, 29 wt% Mo, 3.3 wt% Si. These Alloys are being used for manufacturing guides for hot rolling seamless steel pipes. Alloy 2 and Alloy 3 are being tested as wear segments used inside a 2nd generation ethanol reactor. Tests were performed using three 0.1 g/cm 3 slurries composed by SiO 2 , Al 2 O 3 , and SiC particles, in a distilled water suspension. A load of 0.3 N was applied, the rotational speed was 20 rpm and the total sliding distance 48 m. Analysis of the Alloys' tribosurfaces – by Optical Microscopy, Scanning Electron Microscopy and Contact Stylus Profilometry – showed abrasive size, shape and hardness may influence wear coefficients significantly. Tests performed with SiC and Al 2 O 3 slurries resulted in greater wear rates than those with SiO 2 slurry. Alloy 1 showed the greatest wear coefficient, in comparison with the other two experimental Alloys, due to the absence of hard second phase precipitates in its microstructure. The variation of the wear coefficients as a function of abrasive hardness (H a ) and the compound alloy hardness (H s ) showed a linear correlation (R 2 = 0.73). Two-body abrasion (grooving wear) was the dominant wear micro-mechanism observed for all tests. Alloy 2, containing Laves phase showed a transition from ductile to brittle wear mechanism when tested with alumina slurries. The SiC slurry gave the highest worn volume among the three tested slurries.
Josep Serraprat - One of the best experts on this subject based on the ideXlab platform.
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adhesion of dental porcelain to cast milled and laser sintered cobalt Chromium Alloys shear bond strength and sensitivity to thermocycling
Journal of Prosthetic Dentistry, 2014Co-Authors: Josep Serraprat, Jordi Canobatalla, Josep Cabratosatermes, Oscar FiguerasalvarezAbstract:Statement of problem New technologies have led to the introduction of new materials, so an evaluation of the adhesion of ceramics to these materials is needed. Purpose The purpose of this study was to compare the shear bond strength of dental porcelain to cast, milled, and laser-sintered cobalt-Chromium Alloys, and to investigate the adhesive bond and failure type after thermocycling, 90 metal cylinders (10 mm diameter and 10 mm height) were prepared from cast (30 specimens), milled (30 specimens), and laser-sintered (30 specimens) Alloys. Material and methods Ceramic cylinders (2.5 mm diameter and 4 mm length) were fused to the alloy cylinders. For each group, 15 specimens were thermocycled 5500 times at temperatures between 4°C and 60°C before testing. After testing, the specimen surfaces were visually examined to determine the failure mode. Differences in adhesion values according to manufacturing method, testing condition (thermocycling or no thermocycling), and interaction between the factors were evaluated with a 2-way ANOVA. The χ 2 test (95% confidence level) was performed to determine whether the failure mode was associated with the testing condition. Results Adhesion strengths for the nonthermocycled specimens were 42.79 ±14.14 MPa (cast), 37.56 ±9.18 MPa (milled), and 29.09 ±6.95 MPa (laser-sintered), and, for the thermocycled specimens, 16.52 ±8.96 MPa (cast), 22.21 ±13.25 MPa (milled), and 24.28 ±10.13 MPa (laser-sintered). Two-way ANOVA results indicated no statistically significant differences in adhesion among the manufacturing methods ( P =.257), but statistically significant differences were observed according to both testing conditions ( P P =.015). The χ 2 test indicated that the failure mode was not associated with the testing condition (thermocycled, P =.280; nonthermocycled, P =.240). Conclusions The porcelain adhesion values for all the materials were adequate for clinical applications. No significant adhesion differences were observed between cast, milled, and laser-sintered specimens, or among thermocycled and nonthermocycled laser-sintered specimens. However, significant adhesion differences were observed among the thermocycled and nonthermocycled cast and the milled specimens.
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adhesion of dental porcelain to cast milled and laser sintered cobalt Chromium Alloys shear bond strength and sensitivity to thermocycling
Journal of Prosthetic Dentistry, 2014Co-Authors: Josep Serraprat, Jordi Canobatalla, Josep Cabratosatermes, Oscar FiguerasalvarezAbstract:STATEMENT OF PROBLEM: New technologies have led to the introduction of new materials, so an evaluation of the adhesion of ceramics to these materials is needed. PURPOSE: The purpose of this study was to compare the shear bond strength of dental porcelain to cast, milled, and laser-sintered cobalt-Chromium Alloys, and to investigate the adhesive bond and failure type after thermocycling, 90 metal cylinders (10 mm diameter and 10 mm height) were prepared from cast (30 specimens), milled (30 specimens), and laser-sintered (30 specimens) Alloys. MATERIAL AND METHODS: Ceramic cylinders (2.5 mm diameter and 4 mm length) were fused to the alloy cylinders. For each group, 15 specimens were thermocycled 5500 times at temperatures between 4°C and 60°C before testing. After testing, the specimen surfaces were visually examined to determine the failure mode. Differences in adhesion values according to manufacturing method, testing condition (thermocycling or no thermocycling), and interaction between the factors were evaluated with a 2-way ANOVA. The χ(2) test (95% confidence level) was performed to determine whether the failure mode was associated with the testing condition. RESULTS: Adhesion strengths for the nonthermocycled specimens were 42.79 ±14.14 MPa (cast), 37.56 ±9.18 MPa (milled), and 29.09 ±6.95 MPa (laser-sintered), and, for the thermocycled specimens, 16.52 ±8.96 MPa (cast), 22.21 ±13.25 MPa (milled), and 24.28 ±10.13 MPa (laser-sintered). Two-way ANOVA results indicated no statistically significant differences in adhesion among the manufacturing methods (P=.257), but statistically significant differences were observed according to both testing conditions (P<.001) and interaction between the factors (P=.015). The χ(2) test indicated that the failure mode was not associated with the testing condition (thermocycled, P=.280; nonthermocycled, P=.240). CONCLUSIONS: The porcelain adhesion values for all the materials were adequate for clinical applications. No significant adhesion differences were observed between cast, milled, and laser-sintered specimens, or among thermocycled and nonthermocycled laser-sintered specimens. However, significant adhesion differences were observed among the thermocycled and nonthermocycled cast and the milled specimens.
S J Visco - One of the best experts on this subject based on the ideXlab platform.
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Chromium vaporization of bare and of coated iron Chromium Alloys at 1073 k
Solid State Ionics, 2007Co-Authors: Hideto Kurokawa, Craig P Jacobson, Lutgard C Dejonghe, S J ViscoAbstract:Abstract Suppression of Chromium vaporization from oxidation scales formed on ferritic stainless steel, when used on the cathode side of Solid Oxide Fuel Cells (SOFC), is a most important issue, since gaseous Chromium species cause deposition of Chromium oxide on electrolyte or electrode materials. This phenomenon leads to deterioration of the cell performance. The Chromium vaporization rates of bare and of coated iron–Chromium Alloys were measured at 1073 K. The effect of ceramic coating layers, deposited by low-cost aerosol spraying or by dip coating, was evaluated and the morphology of the coating layer was observed. Lanthanum strontium manganese oxide (LSM: La 0.65 Sr 0.3 MnO 3 ), lanthanum strontium cobalt iron oxide (LSCF: La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3 ) and manganese cobalt oxide (MCO: MnCo 2 O 4 ) coatings, formed from submicron powders, decreased Chromium vaporization by a factor of as much as 21–40 at 1073 K. Manganese cobalt oxide and lanthanum strontium Chromium oxide (La 0.7 Sr 0.3 CrO 3 ) coating, formed from powders prepared by a glycine nitrate combustion synthesis, reduced Chromium vaporization by factors of only 2–3 because the coating layers were porous.