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Journal Details
Format
Journal
eISSN
2083-4799
ISSN
1730-2439
First Published
23 Sep 2008
Publication timeframe
4 times per year
Languages
English

Search

Volume 8 (2008): Issue 3 (September 2008)

Journal Details
Format
Journal
eISSN
2083-4799
ISSN
1730-2439
First Published
23 Sep 2008
Publication timeframe
4 times per year
Languages
English

Search

6 Articles
Open Access

Application of Transmission Electron Microscopy in Investigations of Structural Anisotropy of NdFeB Magnets

Published Online: 20 Jan 2009
Page range: 4 - 10

Abstract

Application of Transmission Electron Microscopy in Investigations of Structural Anisotropy of NdFeB Magnets

Rapid quenched powdered ribbons Nd13.6Co6.6Ga0.6B5.5Fe73.7 (at. %) were hot pressed at 700° C. Next, the alloys were subjected to die-upset process through heating to 600, 750 and 1000° C and forged at a rate of έ = 1x10-3 s-1 to the stage of deformation equal to ε = 60%. Directional grain growth occurs in the material during this treatment, which is beneficial due to the anisotropic magnetic properties obtained in such materials. Detailed analysis performed using transmission electron microscopy shows the tendency of micro structural changes in the magnet resulting from the application of different temperatures of the processes.

Keywords

  • NdFeB magnets
  • die-upset forged magnets
  • transmission electron microscopy
  • micro-beam diffraction
Open Access

Underwater Welding - A Review

Published Online: 20 Jan 2009
Page range: 11 - 22

Abstract

Underwater Welding - A Review

The paper describes principles of underwater welding and recent trends in research works undertaken for enhance welding technology and properties of underwater welds. Department of Materials Technology and Welding at Gdansk University of Technology (GUT) has been involved in underwater welding research for over 25 years. Investigations include technology of underwater welding, and weld properties examinations. All tests have been performed with the use of self designed stands allow to perform welds in shallow depths as well as the depths up to 1000 m. The main investigation directions performed at the Department of Materials Technology and Welding are presented:

Weldability of HSLA steel and factors influencing susceptibility to cold cracking of welded joints.

The effects of wet welding conditions on diffusible hydrogen amount in the welds.

The effects of heat input, underwater welding depths and composition of shielded gases on welds toughness.

Keywords

  • underwater welding
  • wet welding
  • dry welding
  • local cavity
  • weldability of steel
Open Access

Modification of the Microstructure and Properties of Laminate Titanium Alloy - TiAl Intermetallic Phases Composites By A Duplex Surface Engineering Treatment

Published Online: 20 Jan 2009
Page range: 23 - 31

Abstract

Modification of the Microstructure and Properties of Laminate Titanium Alloy - TiAl Intermetallic Phases Composites By A Duplex Surface Engineering Treatment

Laminate TiAl3 - titanium alloy composites have unique mechanical properties which result from a combination of the properties of the Ti-Al type intermetallic phases, such as the high stiffness and low density, and the properties of the titanium alloy, primarily its high ductility. These composite materials have already been used in industry, but their application is limited by the low resistance to frictional wear and to oxidation at elevated temperatures. The process of diffusion bonding of titanium alloys with an aluminum foil, followed by magnetron sputtering combined with glow discharge-assisted oxidizing, yields a gradient-type material, i.e. a laminate composite built of the TiAl3-reinforced titanium alloy with a diffusion surface layer of the Al2O3+Ti-Al intermetallic phase type.

The paper presents the results of examination of the structure (by optical, SEM and TEM microscopy), phase composition, chemical composition, frictional wear resistance of the Al2O3+TixAly intermetallic composite surface layers produced on the composites, described above, by a duplex method that combines magnetron sputtering and plasma oxidizing processes. The composite surface layers have a diffusion character, and their microstructure, thickness and phase composition can be modified by modifying the parameters of the hybrid process, in particular the parameters of the glow discharge oxidizing, since these decide about whether the structure of the layer is nano-crystalline or fine-grained and thereby about the properties of the laminate composite.

Keywords

  • composites
  • trialuminides
  • tribological properties
  • coatings
  • wear-resistant applications
Open Access

Effects of the Time and Temperature on the Oxide Scale Formed on the Cobalt Alloys

Published Online: 20 Jan 2009
Page range: 32 - 37

Abstract

Effects of the Time and Temperature on the Oxide Scale Formed on the Cobalt Alloys

The cobalt base PTA (Plasma Transferred Arc) clad layers were investigated under different temperature and time of oxidation. The microstructure of the clads after oxidation demonstrated degradation process which led to the decomposition of the dendrite boundaries. Chemical compositions of the formed scales were depending on the oxidation temperature, chemical composition of the alloy, especially small addition of the silicon, and time of the exposition.

Keywords

  • cobalt base alloy
  • oxidation scale silicon
Open Access

Structure and Properties of the Glow Discharge Nitrided Layers Produced on Austenitic Steel

Published Online: 20 Jan 2009
Page range: 38 - 48

Abstract

Structure and Properties of the Glow Discharge Nitrided Layers Produced on Austenitic Steel

The study is concerned with the nitrided layers produced on ‘medical’ steel of the 316L (00H17N14M2) grade at a temperature of 450°C. The results of the microstructural observations performed by TEM and of the phase analysis of the layers are presented and discussed. The examinations were conducted in the regions extending from the surface down to a depth of about 25 um. The near-surface zone appeared to contain nitrogen austenite and fine precipitates. There were also certain phases in the lamellar form. Because of the applicative aspect of the glow discharge nitriding of 316 steel, the examinations also included its mechanical strength, in particular the static tensile strength and the low-cycle fatigue strength. The static tensile tests showed no significant differences in the yield stress between the samples in the starting state and those subjected to the low-temperature glow discharge assisted nitriding. The low-cycle fatigue tests (which, in view of the differences between the properties of the untreated material and the nitrided layers, can be classified among the most severe mechanical tests) either, indicated no essential differences in the fatigue properties of the samples subjected to the surface treatments conducted under various conditions.

Keywords

  • nitriding
  • austenitic steel
  • glow discharge
  • transmission electron microscopy
  • fatigue tests
Open Access

Microbiological Corossion of Metallic Products as a Result of Biofilm

Published Online: 20 Jan 2009
Page range: 49 - 54

Abstract

Microbiological Corossion of Metallic Products as a Result of Biofilm

One of indispensable conditions for microbiological corrosion to appear is the formation of biofilm on the surface of the metal. That is the biological surficial covering, which contains biologically active microorganisms along with their metabolical compounds. The biofilm is a frequent form of microorganisms existence in water environment. It prevents from diffusion of the metabolic products created by separate cells of microcolonies. It causes that the side products of metabolic changes may gather close to the metal surface. If the metal surface is not resistable to their influence some corrosion processes may occur. The article shows the results of the research of the metallic specimens surface in the environment of three different bacteria types.

Keywords

  • biofilm
  • microbiological corrosion
  • metals
  • bacteria
6 Articles
Open Access

Application of Transmission Electron Microscopy in Investigations of Structural Anisotropy of NdFeB Magnets

Published Online: 20 Jan 2009
Page range: 4 - 10

Abstract

Application of Transmission Electron Microscopy in Investigations of Structural Anisotropy of NdFeB Magnets

Rapid quenched powdered ribbons Nd13.6Co6.6Ga0.6B5.5Fe73.7 (at. %) were hot pressed at 700° C. Next, the alloys were subjected to die-upset process through heating to 600, 750 and 1000° C and forged at a rate of έ = 1x10-3 s-1 to the stage of deformation equal to ε = 60%. Directional grain growth occurs in the material during this treatment, which is beneficial due to the anisotropic magnetic properties obtained in such materials. Detailed analysis performed using transmission electron microscopy shows the tendency of micro structural changes in the magnet resulting from the application of different temperatures of the processes.

Keywords

  • NdFeB magnets
  • die-upset forged magnets
  • transmission electron microscopy
  • micro-beam diffraction
Open Access

Underwater Welding - A Review

Published Online: 20 Jan 2009
Page range: 11 - 22

Abstract

Underwater Welding - A Review

The paper describes principles of underwater welding and recent trends in research works undertaken for enhance welding technology and properties of underwater welds. Department of Materials Technology and Welding at Gdansk University of Technology (GUT) has been involved in underwater welding research for over 25 years. Investigations include technology of underwater welding, and weld properties examinations. All tests have been performed with the use of self designed stands allow to perform welds in shallow depths as well as the depths up to 1000 m. The main investigation directions performed at the Department of Materials Technology and Welding are presented:

Weldability of HSLA steel and factors influencing susceptibility to cold cracking of welded joints.

The effects of wet welding conditions on diffusible hydrogen amount in the welds.

The effects of heat input, underwater welding depths and composition of shielded gases on welds toughness.

Keywords

  • underwater welding
  • wet welding
  • dry welding
  • local cavity
  • weldability of steel
Open Access

Modification of the Microstructure and Properties of Laminate Titanium Alloy - TiAl Intermetallic Phases Composites By A Duplex Surface Engineering Treatment

Published Online: 20 Jan 2009
Page range: 23 - 31

Abstract

Modification of the Microstructure and Properties of Laminate Titanium Alloy - TiAl Intermetallic Phases Composites By A Duplex Surface Engineering Treatment

Laminate TiAl3 - titanium alloy composites have unique mechanical properties which result from a combination of the properties of the Ti-Al type intermetallic phases, such as the high stiffness and low density, and the properties of the titanium alloy, primarily its high ductility. These composite materials have already been used in industry, but their application is limited by the low resistance to frictional wear and to oxidation at elevated temperatures. The process of diffusion bonding of titanium alloys with an aluminum foil, followed by magnetron sputtering combined with glow discharge-assisted oxidizing, yields a gradient-type material, i.e. a laminate composite built of the TiAl3-reinforced titanium alloy with a diffusion surface layer of the Al2O3+Ti-Al intermetallic phase type.

The paper presents the results of examination of the structure (by optical, SEM and TEM microscopy), phase composition, chemical composition, frictional wear resistance of the Al2O3+TixAly intermetallic composite surface layers produced on the composites, described above, by a duplex method that combines magnetron sputtering and plasma oxidizing processes. The composite surface layers have a diffusion character, and their microstructure, thickness and phase composition can be modified by modifying the parameters of the hybrid process, in particular the parameters of the glow discharge oxidizing, since these decide about whether the structure of the layer is nano-crystalline or fine-grained and thereby about the properties of the laminate composite.

Keywords

  • composites
  • trialuminides
  • tribological properties
  • coatings
  • wear-resistant applications
Open Access

Effects of the Time and Temperature on the Oxide Scale Formed on the Cobalt Alloys

Published Online: 20 Jan 2009
Page range: 32 - 37

Abstract

Effects of the Time and Temperature on the Oxide Scale Formed on the Cobalt Alloys

The cobalt base PTA (Plasma Transferred Arc) clad layers were investigated under different temperature and time of oxidation. The microstructure of the clads after oxidation demonstrated degradation process which led to the decomposition of the dendrite boundaries. Chemical compositions of the formed scales were depending on the oxidation temperature, chemical composition of the alloy, especially small addition of the silicon, and time of the exposition.

Keywords

  • cobalt base alloy
  • oxidation scale silicon
Open Access

Structure and Properties of the Glow Discharge Nitrided Layers Produced on Austenitic Steel

Published Online: 20 Jan 2009
Page range: 38 - 48

Abstract

Structure and Properties of the Glow Discharge Nitrided Layers Produced on Austenitic Steel

The study is concerned with the nitrided layers produced on ‘medical’ steel of the 316L (00H17N14M2) grade at a temperature of 450°C. The results of the microstructural observations performed by TEM and of the phase analysis of the layers are presented and discussed. The examinations were conducted in the regions extending from the surface down to a depth of about 25 um. The near-surface zone appeared to contain nitrogen austenite and fine precipitates. There were also certain phases in the lamellar form. Because of the applicative aspect of the glow discharge nitriding of 316 steel, the examinations also included its mechanical strength, in particular the static tensile strength and the low-cycle fatigue strength. The static tensile tests showed no significant differences in the yield stress between the samples in the starting state and those subjected to the low-temperature glow discharge assisted nitriding. The low-cycle fatigue tests (which, in view of the differences between the properties of the untreated material and the nitrided layers, can be classified among the most severe mechanical tests) either, indicated no essential differences in the fatigue properties of the samples subjected to the surface treatments conducted under various conditions.

Keywords

  • nitriding
  • austenitic steel
  • glow discharge
  • transmission electron microscopy
  • fatigue tests
Open Access

Microbiological Corossion of Metallic Products as a Result of Biofilm

Published Online: 20 Jan 2009
Page range: 49 - 54

Abstract

Microbiological Corossion of Metallic Products as a Result of Biofilm

One of indispensable conditions for microbiological corrosion to appear is the formation of biofilm on the surface of the metal. That is the biological surficial covering, which contains biologically active microorganisms along with their metabolical compounds. The biofilm is a frequent form of microorganisms existence in water environment. It prevents from diffusion of the metabolic products created by separate cells of microcolonies. It causes that the side products of metabolic changes may gather close to the metal surface. If the metal surface is not resistable to their influence some corrosion processes may occur. The article shows the results of the research of the metallic specimens surface in the environment of three different bacteria types.

Keywords

  • biofilm
  • microbiological corrosion
  • metals
  • bacteria

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