Metallographic polishing

Preferential corrosion or attack at many other types of crystal defect may also be best illustrated during the etching of metallographically polished... 

The properties and performance of cemented carbide tools depend not only on the type and amount of carbide but also on carbide grain size and the amount of binder metal. Information on porosity, grain size and distribution of WC, solid solution cubic carbides, and the metallic binder phase is obtained from metallographically polished samples. Optical microscopy and scanning and transmission electron microscopy are employed for microstructural evaluation. Typical microstructures of cemented carbides are shown in Figure 3. 

Scratch Test. The scratch microhardness test is a refinement of the Mohs test. The comer of a cubic diamond is drawn across the surface of a metallographically polished sample under a constant load, usually 29.4 N (3 kgf). The width of the resultant Vee groove scratch varies inversely with the hardness of the material displaced where H = scratch hardness number and A = groove width in micrometers. 

The nickel single crystal(MARZ grade 99.995%, supplied by MRC) was metallographically polished down to 1 pm diamond paste, then chemically polished as described by Graham and Cohen (15). Transmission x-ray diffraction measurements confirmed the (100) direction of. the face to 0,0.5°. The specimen, of area o>2 cm2, was spot-welded to a nickel rod fastened to the specimen manipulator. It could be heated by electron bombardment or radiativity and cooled to vloO K through the nickel rod and a LN -cooled copper braid. A control unit held the crystal temperature (via a chromel-alumel thermocouple spot-welded to the back of the crystal) constant to within 1 K. 

L.E. Samuels, Metallographic Polishing by Mechanical Methods, Pitman, London, 1967. 

Pig. 3. Taper section of a metallographically polished brass surface. Taper ratio 10.9. X 2000 before reduction for publication, (a) Etched in ferric chloride reagent to show the fragmented layer (cf. with Figs.l(a)and2(a)). (b) Etched to develop slip-line traces showing the full extent of the plastically-deformed layer, (cf. with Fig. 2(b)). 

Fig. 8. Taper sections of a metallographically polished zinc surface. Isolated twins are associated With some of the surface scratches. (Arrows indicate the section line). Taper ratio 10.5. X1500-...

Perhaps the most informative work has been that of Jacquet (16), Samuels (7,10), and Thomas sen and McCutcheon (52) on 70 30 brass Wulff (44), and Samuels and Wall work (36) on austenitic steels Samuels and Wallwork (37) on zinc and Vacher (23) on steel, copper and aluminum. Most of the measurements in the references quoted pertain to metallographic abrasion processes, but they also include standard machining operations (35,36,41,51), metallographic polishing (7,16,23,... 

Platinum plates with 1 cm area per side were metallographically polished to a mirror finish, rinsed with distilled water, and flamed just before exposure to sea water for either ellipsometric or contact angle measurements. The platinum plates were wetted with photo-oxidized sea water before immersing into experimental sea water, so that passage of the surface through the air—sea water interface would not cause any film present there to be transferred to the plate. For the same reason plates removed from the experimental sea water were immediately immersed while still visibly wet in photo-oxidized sea water and then rinsed. 

Specimen preparation involves wet grinding to remove the surface layer, which may be decarburized or otherwise nonrepresentative of the bulk of the specimen, followed by standard metallographic polishing and etching. This procedure ensures a flat, reproducible surface for the x-ray examination, and allows a preliminary examination of the specimen to be made with the microscope. In grinding and polishing, care should be taken not to produce excessive heat or plastic deformation which would cause partial decomposition of both the martensite and austenite. 

Samuels, L. E. "Metallographic Polishing by Mechanical Methods" Second Edition, American Elsevier New York, 1971. 

Figure 12 shows the A-iji signature for the growth of a barrier layer on a super-pure aluminium electrode which had been metallographically polished. The points represent steady values which were achieved after polarisation with a constant potential across a two-electrode cell. The potential was advanced manually after each point had been recorded, up to a maximum of 60 V. Upon disconnecting the cell, the optical signal remained constant and... 

Transverse sections were prepared by standard metallographic polishing techniques with one addition involving as a first step, coating the surface with a gold layer by sputtering. This enabled identification of the outer gas interface during subsequent analysis. 

Source L.E. Samuals. Metallographic Polishing.. American Society for Metals, Metals Park, OH (1982). 

Note heavy carburization of exposed (right) surface of tube gjecimen nickel plated after test to preserve edges during metallographic polishing... 

Another prominent example for accidental microstmcture modification is white layers, more or less thick surface layers in hardened materials. They show a clearly increased hardness and a resistance against etching, so that they appear white in metallographic polished sections. The phenomenon appears in certain machining processes like grinding or hard machining, but also on railroad tracks, as a result of mechanic and thermal influences. Below the white layer, there is also more or less thick, tempered zone with reduced hardness. Microstmctural analyses of white layers lead to different results (Guo and Sahni 2004). 

Samuels, L.E. 2003. Metallographic polishing by mechanical methods, 4th ed. 400. Materials Park,... 

Figure 3.496. SEM micrographs of metallographically polished surfaces of the short glass fiber/PET composites with different fiber weight fractions (w/o = weight % z = thickness direction x = mould filling direction MFD) [1267],...

The experimental procedures specific to the UHV-EC [7] and STM-EC [5c,8] investigations have been described in detail elsewhere. UHV-EC work, carried out at Texas A M University (College Station, TX) employed a commercially oriented and metallographically polished, 99.9999%-pure Pd(llO) single-crystal electrode. STM-EC studies, undertaken at Tehoku University (Sendai, Japan) were done with Pd(llO) single-crystal surfaces prepared from 99.995%-pure polyciystalline Pd wires by the method of Clavilier [3] modified to compensate for the imique chemical properties of Pd metal. Commercial instruments were used in the UHV-EC (Perkin-Elmer, Eden Prairie, MN) and STM-EC (Digital Instruments, Santa Barbara, CA) experiments. 

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