General

HEAT-RESISTANT ALLOYS cover a wide range of chemical compositions, microstructural constituents, and mechanical properties. This article summarizes metallographic techniques and microstructural constituents for three types of cast and wrought heat-resistant alloys: iron-base, nickel-base, and cobalt-base. The metallographic methods discussed also are suitable for preparing both cast and wrought heat-resistant alloys; microstructural constituents are quite similar except for obvious differences in homogeneity and porosity.
The procedures used to prepare metallographic specimens of cast or wrought heat-resistant grades are quite similar to those for ironbase alloys, especially stainless steels (see the Section “Metallographic Techniques” in this Volume). Aspects particularly significant to the preparation of cast or wrought heat-resistant alloys are emphasized. Tables 1 to 3 list the nominal compositions of Fe-Ni-Cr Alloy Casting Institute H-series alloys and other iron-nickel,
nickel-, and cobalt-base cast and wrought heatresistant alloys, respectively.

DOWNLOAD THE PAPER HERE

Introduction

Electron backscattered diffraction (EBSD) is performed with the scanning electron microscope (SEM) to provide a wide range of analytical data; e.g., crystallographic orientation studies, phase identification and grain size measurements. A diffraction pattern can be obtained in less than a second, but image quality is improved by utilizing a longer scan time. Grain mapping requires development of diffraction patterns at each pixel in the field and is a slower process. The quality of the diffraction pattern, which influences the confidence of the indexing of the diffraction pattern, depends upon removal of damage in the lattice due to specimen preparation. It has been claimed that removal of this damage can only be obtained using electrolytic polishing or ionbeam polishing. However, the use of modern mechanical preparation methods, equipment and consumables does yield excellent quality diffraction patterns without use of dangerous electrolytes and the problems and limitations associated with electropolishing and ion-beam polishing. Basically, if mechanical preparation results in quality polarized light images of noncubic crystal structure elements and alloys (e.g., Sb, Be, Hf, -Ti, Zn, Zr), or color tint etching of cubic, or non-cubic crystal structure elements or alloys produces high-quality color images, then the surface is free of harmful residual preparation damage and EBSD patterns with high pattern quality indexes will be obtained. Because of the acute angle between the specimen and the electron beam (70 – 74 ), exceptional surface flatness is also necessary for best results.

DOWNLOAD THE PAPER HERE

Abstract

Metallographic sample preparation methods for porous coated implant devices can be difficult due to inadequate fill of the mounting materials into the porous metallic structures. Inadequate fill of the mounting material during sample preparation leads to problems such as edge rounding, uneven etching, and metal smearing during polishing. These problems make proper microstructural identification and analysis difficult and/or inaccuate.

DOWNLOAD THE PAPER HERE

Specimen Mounting Program

Implant Specimens

• Acetabular cup: Ti-6Al-4V substrate, CP Ti wire
• Acetabular Cup: Ti-6Al-4V substrate, CP Ti Powder, Ta Beads
• Femoral Hip Stem: Co-Cr-Mo with Co-Cr-Mo Beads
• Femoral Knee: Co-Cr-Mo with Co-Cr-Mo Wire

Mounting Procedures

• PhenoCure™thermosetting phenolic resin
• Electroless Ni-plate/EpoMet® thermosetting resin
• Vacuum impregnate with low-viscosity EpoThin® epoxy resin
• Vacuum impregnate with EpoHeat™epoxy resin
• SamplKwick® cast acrylic resin

DOWNLOAD THE PRESENTATION HERE

In 1925 in the UK, Smith and Sandland developed an indentation test that used a squarebased pyramidal-shaped indenter made of diamond[1]. The test was developed because the Brinell test (introduced in 1900), which (until recently) used a round hardened steel ball indenter, could not test steels harder than ~450 HB (~48 HRC). They chose this shape with an angle of 136° between opposite faces to obtain hardness numbers that would be as close as possible to Brinell hardness numbers for the same specimens over the usable Brinell range. This made the Vickers test easy to adopt, and it rapidly gained acceptance. The Vickers test has the great advantage of one hardness scale being used to test all materials, unlike the 30 different Rockwell test scales, each yielding numbers between ~20 and ~100.

DOWNLOAD THE PAPER HERE

Nature of Light in Microscopy

Amplitude – light intensity
Wavelength – color;
Phase displacement;
Polarization – one plane of vibration

Laws of Refraction and Reflection

Part of the incident light ray is reflected and part is
refracted; the angle of reflection equals the angle of
incidence, i.e., θ = Φ

DOWNLOAD THE PRESENTATION HERE

What is Metallography

Metallography is the study of microstructure, how it is produced by composition and processing control, and the relationship between microstructure, mechanical and physical properties, and performance or service behavior. To examine the microstructure, we must prepare specimens properly so that the true structure, free of artifacts due to preparation, can be observed and properly identified, measured and interpreted.

What is Microstructure

Microstructure is the structure of a suitably prepare specimen as revealed by a microscope Microstructure consists of phases and/or constituents.
A phase is a physically homogeneous, mechanically separable portion of a material system. A constituent is a phase or combination of phases, which occurs in a characteristic configuration in an alloy microstructure.

DOWNLOAD THE PRESENTATION HERE