Metallographic Examination of Welds

Metallographic Examination of Welds

DOWNLOAD THE PRESENTATION HERE

Last Updated on Wednesday, 13 February 2013 14:08

Hits: 1339

Read more: Metallographic Examination of Welds

What is Metallography

Metallography is the branch of science dealing with the study of the consititution and structure of metals and alloys, its control through processing, and its influence on properties and behavior. Its original implementation was limited by the resolution of the reflected light microscope used to study specimens. This limitation has been overcome by the development of transmission and scanning electron microscopes (TEM and SEM). The analysis of x-rays generated by the interaction of electron beams with atoms at or near the surface, with wavelength- or energy-dispersive spectrometers (WDS, EDS) with the SEM or the electron microprobe analyzer (EMPA), has added quantitative determination of local compositions, e.g., of intermediate phases, to the deductions based upon observations. Introduction of metrological and stereological methods, and the development of computer-aided image analyzers, permits measurement of microstructural features. Crystallographic data can be obtained using classic x-ray diffraction methods using a diffractometer, or diffraction analysis can be performed with the TEM using selected area or convergent-beam electron diffraction (SAD and CBED) techniques, and more recently with the SEM with the orientation-imaging (EBSD) procedure. There is a wide variety of very sophisticated electron or ion devices that can be utilized to characterize surfaces and interfaces, but these devices are generally restricted in availability due to their high cost.

DOWNLOAD THE PAPER HERE

Last Updated on Monday, 11 February 2013 20:37

Hits: 1337

Read more: What is Metallography

Understanding Heat Treatment Results Using Metallography - Version 2

As Hot Rolled Microstructures

  • Microstructure of hot-rolled Fe –0.94% C –0.51% Mn–0.32% Si –1.34% Cr alloy steel revealing a fully pearliticmatrix. Picralrevealed a network of cementite in the prior-austenite grain boundaries (arrows). This is not visible using nital. Originals at 1000X.
  • Microstructure of as-rolled Fe –1.31% C –0.35% Mn–0.25% Si high-carbon water hardenabletool steel. Note the Widmanstättenintragranularcementite that precipitated as pro-eutectoid cementite before the eutectoid reaction. Originals at 1000X.
  • Microstructure of the as-rolled Fe –1.31% C –0.35% Mn–0.25% Si specimen with the intergranular carbide network clearly visible after etching with alkaline sodium picrate, 90 °C –60 s. Original at 500X magnification. Note also some intragranular Widmanstätten cementite.

DOWNLOAD THE PRESENTATION HERE

Last Updated on Monday, 11 February 2013 20:36

Hits: 1194

Read more: Understanding Heat Treatment Results Using Metallography - Version 2

Understanding Heat Treatment Results Using Metallography - Version 1

As Hot Rolled Microstructures

  • Microstructure of hot-rolled Fe –0.12% C –0.23% Mn –0.17% Si –0.74% Mo revealing a ferrite-pearlite microstructure with small patches of martensite (arrows). The many small black particles are small patches of pearlite, not inclusions. Originals at 1000X.
  • Microstructure of hot-rolled Fe –0.94% C –0.51% Mn –0.32% Si –1.34% Cr alloy steel revealing a fully pearlitic matrix. Picral revealed a network of cementite in the prior-austenite grain boundaries (arrows). This is not visible using nital. Originals at 1000X.
  • Microstructure of as-rolled Fe –1.31% C –0.35% Mn –0.25% Si high-carbon water hardenable tool steel. Note the Widmanstätten intragranular cementite that precipitated as pro-eutectoid cementite before the eutectoid reaction. Originals at 1000X.

DOWNLOAD THE PRESENTATION HERE

Last Updated on Monday, 11 February 2013 20:34

Hits: 1245

Read more: Understanding Heat Treatment Results Using Metallography - Version 1

Thermal Spray Metallography for the 21st Century

Sectioning - Lessond Learned

  • Abrasive Wheels-ultrathin abrasive blades are superior to standard production wheels.
  • Diamond Wafering Blades-are the best universal blades producing the least amount of sectioning damage.

Mounting - A Better Way

  • Compression Mounting-limited to non-friable, very low porosity metallic coatings.
  • Castable Epoxy Mounting-versatile for all types of coatings without introducing damage.
  • Vacuum Impregnation-useful for infiltrating open pores in coatings. Most effective when using castable epoxies with viscosity less than 500 cps.
  • Pressure Impregnation-produces maximum penetration of castable epoxies using pressure of 1500 psi.

DOWNLOAD THE PRESENTATION HERE

Last Updated on Monday, 11 February 2013 20:33

Hits: 1024

Read more: Thermal Spray Metallography for the 21st Century

The SEM as a Metallographic Tool

Influence of Preparation on Image Quality

Back-scatter electron images of as-polished 2205 duplex stainless steel shows the improvement in image quality by using the best preparation methods.

Image Contrast Modes

  • EmissiveMode – low-energy secondary electrons (come from the surface to ~10 nm depth)
  • ReflectiveMode – higher-energy backscattered electrons (come from a much greater depth)
  • AbsorptiveMode – detect signal flowing through the specimen to ground (inverse of BSE image)
  • X-RayMode – characteristic x-rays generated by the incident beamto show the distribution of elements at, and slightly below, the surface.

DOWNLOAD THE PRESENTATION HERE

Last Updated on Monday, 11 February 2013 20:31

Hits: 1224

Read more: The SEM as a Metallographic Tool

Solidification Structures

Macrostructure of a VIM (vacuum induction melted) ingot of Fe-52% Ni alloy. A slice was cut transverse to the ingot axis and hot acid etched (50% HCl at 70 °C) revealing the solidification pattern. There is a very thin surface zone of small grains. Below the surface, there is a zone of columnar grains and the central portion is equiaxed but coarse. The scale is in inches.

Transverse Concast Discs, 430 SS

Macrostructure of 5-inch square (127 mm) continuously cast billets of type 430 stainless steel (Fe - 0.03% C – 0.34% Mn – 0.48% Si – 17.78% Cr – 0.26% Ni – 0.05% Mo – 0.07% Cu) taken at three random locations along the strand. The discs were cut transverse to the growth direction and were hot acid etched. Note the thin region of fine grains at the surface, the large columnar zone and the central equiaxed zone (of varying coarseness). Note that there are some fine cracks present.

DOWNLOAD THE PRESENTATION HERE

Last Updated on Monday, 11 February 2013 20:29

Hits: 1234

Read more: Solidification Structures

resourcesThe articles and presentations that can be down-loaded from this web site are based upon work done by GFV while employed at Bethlehem Steel (1967-1983), Carpenter Technology (1983-1996), Buehler Ltd. (1996-2009) and Struers (2009-Present) and from the authors consulting work for companies such as, Latrobe Steel, Scot Forge, etc., and from his litigation work. GFV's bylined articles appearing in various issues of the ASM Handbook series have been listed here courtesy of ASM International, Materials Park, Ohio.

Log in to your account or