Relatively few metallographers work with precious metals, other than those used in electronic devices.  Precious metals are very soft and ductile, deform and smear easily, and are quite challenging to prepare. Pure gold is very soft and the most malleable metal known. Alloys, which are more commonly encountered, are harder and somewhat easier to prepare.

Gold is difficult to etch. Silver is very soft and ductile and prone to surface damage from deformation. Embedding of abrasives is a common problem with both gold and silver and their alloys. Iridium is much harder and more easily prepared. Osmium is rarely encountered in its pure form; even its alloys are infrequent subjects for metallographers. Damaged surface layers are easily produced and grinding and polishing rates are low. It is quite difficult to prepare. Palladium is malleable and not as difficult to prepare as most of the precious metals. Platinum is soft and malleable. Its alloys are more commonly encountered. Abrasive embedment is a problem with Pt and its alloys. Rhodium is a hard metal and is relatively easy to prepare. Rh is sensitive to surface damage in sectioning and grinding. Ruthenium is a hard, brittle metal that is not too difficult to prepare. By George Vander Voort

International Thermal Spray Association History and Development of Modern Thermal Spray Guns – Part 2 Using vortex-stabilized units, as described above, coldspray, warm-spray, and hot-spray, each producing impact-fusion, are possible. It is not the same though. Outside water cooling is necessary with nozzle lengths up to 16 in. long using ½ in. bores. The principle…

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Vacuum Pump Practice with Dan Herring Oil Sealed Rotary Vane Pumps, Part 1 Oil sealed rotary vane pumps (aka rotary vane pumps) are the primary pumps on most vacuum systems used in the heat treatment industry. They are also referred to as a “backing” pump when used in combination with a booster pump, or with…

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Front and Bottom Loading Vacuum Furnaces Constructed of the finest materials and craftsmanship, VAC AERO’s high performance vacuum heat treating furnaces are operator friendly and designed to minimize maintenance and downtime to deliver outstanding quality and  value to commercial and in-house heat treaters alike. VAC AERO’s vacuum furnaces are designed for rapid heating rates to…

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Industrial Heating Magazine Effect of Cryogenic Treatment on Properties of Tool Steels The effect of cryogenic treatment (CT) on the properties of ledeburitic tool steels was investigated. CT is also used in conventional heat treatment to improve mechanical properties and wear resistance and decrease the amount of retained austenite. The technology of CT was developed…

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Mission: The International Thermal Spray Association is a professional trade organization dedicated to expanding the use of thermal spray technologies for the benefit of industry and society. History – Early Beginnings The International Thermal Spray Association is closely interwoven with the history of thermal spray development in this hemisphere. Founded in 1948, and once known…

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Welding is a very important joining process and has been used extensively for at least the past 75 years. There is a need to control processes, such as welding, to insure a high quality end result. Over the years there have been many spectacular failures of welded structures, starting with Liberty ship and T-2 tanker failures during WWII, that emphasize this need. Many procedures involving non-destructive and destructive tests are used to study weldments.

Metallographic examination can be performed in-situ by grinding an area on the surface of the weld, its heat affected zones and adjacent base metal (the metal being joined that was unaffected by the temperature of the welding process). This is a reasonably non-destructive evaluation. Destructive examination, where a specimen is removed from either the welded assembly or test coupons, is quite commonly performed. Test coupons are often used to qualify the welder and ensure that the techniques and materials chosen will produce a weld with acceptable soundness and mechanical properties. Post mortems of failed weldments are also examined metallographically using sections removed from the welded assembly, generally after non-destructive examination is completed. By George Vander Voort

For immediate release Oakville, Ontario, July 17, 2012 – VAC AERO is pleased to announce it is launching a new Thermal Spray Coatings column in collaboration with the International Thermal Spray Association, a standing committee of the American Welding Society.  The new column, written by expert technical writers associated with the ITSA SPRAYTIME® newsletter will…

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The first, and obvious, point to make about dimensioning braze fillets on drawings is that once a braze-fillet size is specified on a drawing, it must be inspected and measured to verify compliance. This can be a meaningless and very expensive waste of time for a manufacturer when it comes to braze fillets.

The American Welding Society (AWS) document that is most commonly used for specifying how to properly place such requirements on a drawing is AWS A2.4 “Standard Symbols for Welding, Brazing and Nondestructive Examination.” That document includes numerous illustrations about how to use so-called “welding-arrow symbols” to specify fillet sizes on drawings. Be very careful. by Dan kay

Over the years, a strange question has sometimes been raised by people who are trying to optimize their vacuum brazing procedures. The question usually sounds something like this:

“If vacuum is good for brazing by pumping out the air from the furnace (thus, also removing a lot of the oxygen from the brazing zone that could hurt brazing), and if paste-fluxes are very good at helping to remove any residual oxides that can get onto metal surfaces that are being heated, then, isn’t it reasonable to consider that the combination of brazing in a vacuum along with the use of a paste-flux on the metal surfaces to be brazed would be highly effective for optimal brazing?”. by Dan kay