Patrice Berthod | Université de Lorraine (original) (raw)

materials science by Patrice Berthod

Three series of ternary alloys of the {M-30Cr-xC}-type with M = Co, Ni or Fe and x ranging from 2... more Three series of ternary alloys of the {M-30Cr-xC}-type with M = Co, Ni or Fe and x ranging from 2.5 to 5 wt% were elaborated by casting. Their microstructure characterizations by XRD and SEM show that very high volume fractions in chromium carbides (even more than 50%) may be obtained in a metallic matrix by this way. However graphite may also appear in very low quantities in the carbon-richest alloys. The hardness increases with the carbon content (up to 1000 Hv30kg) but it may be a little lowered when graphite is also present. The results show that very hard alloys may be simply obtained by casting of rather cheap elements.

Papers by Patrice Berthod

ISRN Metallurgy, 2012

Some of the wear-resistant pieces or coatings, constituted of a metallic matrix and of carbides p... more Some of the wear-resistant pieces or coatings, constituted of a metallic matrix and of carbides present in high fractions, are a mix, in similar quantities, of two materials displaying greatly different levels of hardness but also of thermal expansion coefficient. When temperature increases, the second difference of property may lead to particular geometrical behaviours. To study these differences, nine nickel-based, cobalt-based, and iron-based alloys containing very high quantities of carbides were elaborated by foundry. In their as-cast conditions, the microstructures of these alloys were characterized; their hardness and thermal expansion until 1200°C were measured and analysed, with regard to the evolution of the structures predicted by thermodynamic calculations. The hardness of the alloys is high (nickel alloys) or very high (cobalt and iron alloys, 600 Hv and more) while the thermal expansion is greatly influenced by carbides, notably when temperature has become very high. S...

ISRN Corrosion, 2012

A model {minor elements}-free Fe-8Ni-18Cr alloy (wt%) was elaborated by foundry, then cut in seve... more A model {minor elements}-free Fe-8Ni-18Cr alloy (wt%) was elaborated by foundry, then cut in several cylindrical parts which were subjected to compression tests leading to different plastic deformation rates. The axis surface of the obtained samples were characterized in corrosion by impedance spectroscopy in an acid sulphuric solution. The obtained EIS results were plotted in the complex plan of Nyquist and the diagrams were all semicircular but with an average radius decreasing when the deformation rate increased. The plastic deformation obviously induced a decrease in charge transfer resistance, revealing a detrimental effect of the corrosion behaviour as the most often reported in studies involving stationary methods of electrochemical characterization of corrosion. It was also found that the capacitance tends to increase with the rate of plastic deformation by compression.

Defect and Diffusion Forum, 2012

Glass Science and Technology Frankfurt Am Main, 2004

International Journal of Materials Research, Oct 16, 2013

Advances in Science and Technology, Jan 5, 2011

Materials Science and Technology, May 1, 2009

Annales de Chimie Science des Matériaux

Thirteen alloys Co(bal.)-30Cr-0 to 5C (in weight percents) were prepared by foundry, then examine... more Thirteen alloys Co(bal.)-30Cr-0 to 5C (in weight percents) were prepared by foundry, then examined by Electron Microscopy with measurement of the surface fractions of carbides and of graphite if present. The Vickers hardness was measured for all alloys and the values were plotted versus the alloys chemical compositions and versus their microstructures. For less than 3wt.%C the microstructures are hypo-eutectic with presence of dendrites. For higher carbon contents dendrites are replaced by coarse pro-eutectic carbides. Lamellar graphite also appears for 5wt.%C. Hardness increases regularly with the carbon content, from 300 to 650 Hv30, but this increase stops when graphite appears. As shown with alloys additionally prepared the graphite can appear in alloys for carbon contents less than 5wt.% if the chromium content is decreased.

Annales De Chimie Science Des Materiaux, Oct 28, 2009

Materials Science Forum, Dec 3, 2008

... Patrice Berthod, Yassin Hamini and Lionel Aranda ... and embedded in a cold resin, then polis... more ... Patrice Berthod, Yassin Hamini and Lionel Aranda ... and embedded in a cold resin, then polished with SiC paper from 80 to 1,200 grid under water, then finished with a diamond paste 6 m. The samples were examined using a Scanning Electron Microscope (SEM) Philips XL30. ...

International Journal of Materials Research, 2014

Materials Science Forum, 2008

... Patrice Berthod, Yassin Hamini and Lionel Aranda ... and embedded in a cold resin, then polis... more ... Patrice Berthod, Yassin Hamini and Lionel Aranda ... and embedded in a cold resin, then polished with SiC paper from 80 to 1,200 grid under water, then finished with a diamond paste 6 m. The samples were examined using a Scanning Electron Microscope (SEM) Philips XL30. ...

The Open Corrosion Journal, 2011

... Grégory Michel, Patrice Berthod*, Stéphane Mathieu, Michel Vilasi and Pierre Steinmetz Instit... more ... Grégory Michel, Patrice Berthod*, Stéphane Mathieu, Michel Vilasi and Pierre Steinmetz Institut Jean Lamour (UMR CNRS 7198), Department 2 – Chemistry and Physics of Solids and Surfaces, Nancy – University, BP 70239, 54506 Vandoeuvre-lès-Nancy, France ...

The Open Corrosion Journal, 2011

The heating parts of thermogravimetry curves performed for cast alloys in air at high temperature... more The heating parts of thermogravimetry curves performed for cast alloys in air at high temperatures were analysed, after correction from the effects of air buoyancy variation, to characterize the transient oxidation before reaching the targeted temperature for the isothermal stage usually applied thereafter. This was done here for three binary M-30Cr alloys, six ternary M-30Cr-0.4 and 0.8%C alloys, and three M-30Cr-0.4C-6Ta quaternary alloys, heated in synthetic air at 20 K min-1 until 1000, 1100 or 1200°C. The cobalt alloys begin to be oxidized with a sufficient mass gain to be detected by thermogravimetry, earlier than the nickel or iron alloys (i.e. at lower temperatures). The temperature of oxidation start is lowered by the presence of tantalum for the three families of alloys. When the carbon content (or the carbides density) increases in the alloy, the temperature of oxidation start decreases for the cobalt alloys and remains almost constant for the nickel or iron alloys, while the total mass gain due to oxidation during heating increases for the nickel and cobalt alloys and decreases for the iron alloys.

Oxidation of Metals, 2007

Two simple cast nickel alloys Ni-30Cr-0.2C and Ni-30Cr-0.8C were oxidized at 1,000, 1,100 and 1,2... more Two simple cast nickel alloys Ni-30Cr-0.2C and Ni-30Cr-0.8C were oxidized at 1,000, 1,100 and 1,2008C. Their behaviors were characterized using thermogravimetry techniques and their parabolic and chromia volatilization constants were determined by analyzing the m Á dm dt versus Àm curves. The constants obtained were generally in good agreement with experimental mass-gain kinetics and chromium-balance aspects. A higher carbon content i.e., a higher carbides density leads to higher values of the transient linear-oxidation constant K l , of the parabolic constant K p , and obviously also of the volatilization constant K v . Chromium diffusion coefficients through the zone affected by oxidation were calculated from the oxidation kinetics and chromium gradients. They increase when the carbide density increases.

Three series of ternary alloys of the {M-30Cr-xC}-type with M = Co, Ni or Fe and x ranging from 2... more Three series of ternary alloys of the {M-30Cr-xC}-type with M = Co, Ni or Fe and x ranging from 2.5 to 5 wt% were elaborated by casting. Their microstructure characterizations by XRD and SEM show that very high volume fractions in chromium carbides (even more than 50%) may be obtained in a metallic matrix by this way. However graphite may also appear in very low quantities in the carbon-richest alloys. The hardness increases with the carbon content (up to 1000 Hv30kg) but it may be a little lowered when graphite is also present. The results show that very hard alloys may be simply obtained by casting of rather cheap elements.

ISRN Metallurgy, 2012

Some of the wear-resistant pieces or coatings, constituted of a metallic matrix and of carbides p... more Some of the wear-resistant pieces or coatings, constituted of a metallic matrix and of carbides present in high fractions, are a mix, in similar quantities, of two materials displaying greatly different levels of hardness but also of thermal expansion coefficient. When temperature increases, the second difference of property may lead to particular geometrical behaviours. To study these differences, nine nickel-based, cobalt-based, and iron-based alloys containing very high quantities of carbides were elaborated by foundry. In their as-cast conditions, the microstructures of these alloys were characterized; their hardness and thermal expansion until 1200°C were measured and analysed, with regard to the evolution of the structures predicted by thermodynamic calculations. The hardness of the alloys is high (nickel alloys) or very high (cobalt and iron alloys, 600 Hv and more) while the thermal expansion is greatly influenced by carbides, notably when temperature has become very high. S...

ISRN Corrosion, 2012

A model {minor elements}-free Fe-8Ni-18Cr alloy (wt%) was elaborated by foundry, then cut in seve... more A model {minor elements}-free Fe-8Ni-18Cr alloy (wt%) was elaborated by foundry, then cut in several cylindrical parts which were subjected to compression tests leading to different plastic deformation rates. The axis surface of the obtained samples were characterized in corrosion by impedance spectroscopy in an acid sulphuric solution. The obtained EIS results were plotted in the complex plan of Nyquist and the diagrams were all semicircular but with an average radius decreasing when the deformation rate increased. The plastic deformation obviously induced a decrease in charge transfer resistance, revealing a detrimental effect of the corrosion behaviour as the most often reported in studies involving stationary methods of electrochemical characterization of corrosion. It was also found that the capacitance tends to increase with the rate of plastic deformation by compression.

Defect and Diffusion Forum, 2012

Glass Science and Technology Frankfurt Am Main, 2004

International Journal of Materials Research, Oct 16, 2013

Advances in Science and Technology, Jan 5, 2011

Materials Science and Technology, May 1, 2009

Annales de Chimie Science des Matériaux

Thirteen alloys Co(bal.)-30Cr-0 to 5C (in weight percents) were prepared by foundry, then examine... more Thirteen alloys Co(bal.)-30Cr-0 to 5C (in weight percents) were prepared by foundry, then examined by Electron Microscopy with measurement of the surface fractions of carbides and of graphite if present. The Vickers hardness was measured for all alloys and the values were plotted versus the alloys chemical compositions and versus their microstructures. For less than 3wt.%C the microstructures are hypo-eutectic with presence of dendrites. For higher carbon contents dendrites are replaced by coarse pro-eutectic carbides. Lamellar graphite also appears for 5wt.%C. Hardness increases regularly with the carbon content, from 300 to 650 Hv30, but this increase stops when graphite appears. As shown with alloys additionally prepared the graphite can appear in alloys for carbon contents less than 5wt.% if the chromium content is decreased.

Annales De Chimie Science Des Materiaux, Oct 28, 2009

Materials Science Forum, Dec 3, 2008

... Patrice Berthod, Yassin Hamini and Lionel Aranda ... and embedded in a cold resin, then polis... more ... Patrice Berthod, Yassin Hamini and Lionel Aranda ... and embedded in a cold resin, then polished with SiC paper from 80 to 1,200 grid under water, then finished with a diamond paste 6 m. The samples were examined using a Scanning Electron Microscope (SEM) Philips XL30. ...

International Journal of Materials Research, 2014

Materials Science Forum, 2008

... Patrice Berthod, Yassin Hamini and Lionel Aranda ... and embedded in a cold resin, then polis... more ... Patrice Berthod, Yassin Hamini and Lionel Aranda ... and embedded in a cold resin, then polished with SiC paper from 80 to 1,200 grid under water, then finished with a diamond paste 6 m. The samples were examined using a Scanning Electron Microscope (SEM) Philips XL30. ...

The Open Corrosion Journal, 2011

... Grégory Michel, Patrice Berthod*, Stéphane Mathieu, Michel Vilasi and Pierre Steinmetz Instit... more ... Grégory Michel, Patrice Berthod*, Stéphane Mathieu, Michel Vilasi and Pierre Steinmetz Institut Jean Lamour (UMR CNRS 7198), Department 2 – Chemistry and Physics of Solids and Surfaces, Nancy – University, BP 70239, 54506 Vandoeuvre-lès-Nancy, France ...

The Open Corrosion Journal, 2011

The heating parts of thermogravimetry curves performed for cast alloys in air at high temperature... more The heating parts of thermogravimetry curves performed for cast alloys in air at high temperatures were analysed, after correction from the effects of air buoyancy variation, to characterize the transient oxidation before reaching the targeted temperature for the isothermal stage usually applied thereafter. This was done here for three binary M-30Cr alloys, six ternary M-30Cr-0.4 and 0.8%C alloys, and three M-30Cr-0.4C-6Ta quaternary alloys, heated in synthetic air at 20 K min-1 until 1000, 1100 or 1200°C. The cobalt alloys begin to be oxidized with a sufficient mass gain to be detected by thermogravimetry, earlier than the nickel or iron alloys (i.e. at lower temperatures). The temperature of oxidation start is lowered by the presence of tantalum for the three families of alloys. When the carbon content (or the carbides density) increases in the alloy, the temperature of oxidation start decreases for the cobalt alloys and remains almost constant for the nickel or iron alloys, while the total mass gain due to oxidation during heating increases for the nickel and cobalt alloys and decreases for the iron alloys.

Oxidation of Metals, 2007

Two simple cast nickel alloys Ni-30Cr-0.2C and Ni-30Cr-0.8C were oxidized at 1,000, 1,100 and 1,2... more Two simple cast nickel alloys Ni-30Cr-0.2C and Ni-30Cr-0.8C were oxidized at 1,000, 1,100 and 1,2008C. Their behaviors were characterized using thermogravimetry techniques and their parabolic and chromia volatilization constants were determined by analyzing the m Á dm dt versus Àm curves. The constants obtained were generally in good agreement with experimental mass-gain kinetics and chromium-balance aspects. A higher carbon content i.e., a higher carbides density leads to higher values of the transient linear-oxidation constant K l , of the parabolic constant K p , and obviously also of the volatilization constant K v . Chromium diffusion coefficients through the zone affected by oxidation were calculated from the oxidation kinetics and chromium gradients. They increase when the carbide density increases.

Materials Science Forum, 2004

Several cast strengthened superalloys, Ni base and Co base, were exposed to high temperature oxid... more Several cast strengthened superalloys, Ni base and Co base, were exposed to high temperature oxidation for long times and metallographically examined. Different phenomena occurred in the sub-surface microstructure, depending on both alloy and temperature. Thermodynamic modelling was used to know what it happened for carbon during oxidation, then to explain the observed microstructural changes. It appears that carbon atoms either quit the alloy probably after its oxidation into gases, or on the contrary go deeper into the bulk where they promote the precipitation of new carbides by solid state transformation. Thereafter, thermodynamic modelling allowed to know the new local refractoriness of the zones affected by oxidation, then to appreciate the new mechanical properties in the sub-surface.