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<rss version="2.0"><channel><title>Practical Metallography - Practical Metallography</title><link></link><description>Practical Metallography: Practical Metallography</description><language>ENG</language><generator>gabLibrary RSS Component v1.0</generator><pubDate>Mon, 6 Feb 2012 03:11:04 UTC</pubDate><item><title><![CDATA[Contents]]></title><link>http://www.practical-metallography.com/directlink.asp?PM012012</link><author></author><description><![CDATA[]]></description><pubDate>Thu, 12 Jan 2012 23:00:00 UTC</pubDate></item><item><title><![CDATA[Editorial]]></title><link>http://www.practical-metallography.com/directlink.asp?PM012011</link><author></author><description><![CDATA[]]></description><pubDate>Thu, 12 Jan 2012 23:00:00 UTC</pubDate></item><item><title><![CDATA[Investigations on High Temperature MgB Superconductor Wires and Tapes with New Sheath Materials and the Correlation of Their Microstructures and Properties]]></title><link>http://www.practical-metallography.com/directlink.asp?PM110159</link><author></author><description><![CDATA[Long superconducting MgB wires and tapes were produced by the “powder in a tube” method (PIT) using a mechanically alloyed nano-powder consisting of Mg, B and MgB as the precursor material. Both single-core (SC) and multi-core (MC) conductors were made by swaging and wire drawing the powder contained within a new type of sheath material (ODS-Cu) which, amongst others, also has the advantage of thermally stabilising the conductor. Metallographic investigations on specimens of the conductors in the as-drawn condition and after heat treatment were carried out both to monitor the manufacturing process as well as to gain information regarding important parameters such as the changes in hardness and ductility of the sheath and filament occurring during the forming process and the effect which they have on the final properties of the conductors. The metallographic and scanning electron microscopic (SEM) investigations of the microstructures were carried out on longitudinal (LS) and cross (XS) sections of the conductors which made it possible to understand the correlation between the microstructures and properties of the conductors and to draw important conclusions in order to be able to achieve the optimum design and best electrical properties for the finished conductors. By heat treating the cold formed conductor in the temperature range 500 – 650 °C, very good superconducting properties were able to be produced with critical temperatures (Tc) of 36 K and critical current densities (jc) of 10 A/cm2 in fields of 11 T (parallel to the tape surface), measured at 4.2 K. Using this new sheath material, a conductor of over 100 m in length was able to be manufactured.]]></description><pubDate>Thu, 12 Jan 2012 23:00:00 UTC</pubDate></item><item><title><![CDATA[A Three-Dimensional Microstructure Preparation Using Metallographic In-Depth Microsections]]></title><link>http://www.practical-metallography.com/directlink.asp?PM110134</link><author></author><description><![CDATA[Efficient simulation techniques are conceived, amongst other things, for the modelling and visualization of microstructure configurations of materials and structural components in production processes, within a joint research project in which the Karlsruhe, Aalen, and Pforzheim Universities were involved. To this end, it is firstly necessary to determine the structure in all of the three spatial directions (three dimensions) which then will help to establish mathematical simulation algorithms. In the further course of the project, it is also understood that the simulation results are checked up and verified again and again by the respective real structures. These activities indispensably presuppose a precise localization of the structure on several planes and adefinition as to what is realized via so-called in-depth microsections. This makes it necessary to develop and optimize techniques both for the exact maintenance of an x-y local constancy and absolutely accurate depth determination (z coordinate). For this purpose, the Pforzheim University formulated a simple metallographic process technology which is aimed at precisely localizing the structures at a well-defined material removal rate. It is on this basis that structural regions can now be detected on several planes at the same location and a sufficient collection of data can be created for the three-dimensional simulations of polycrystalline grain structures.]]></description><pubDate>Thu, 12 Jan 2012 23:00:00 UTC</pubDate></item><item><title><![CDATA[Pitting Corrosion Induced Fatigue Fracture on a Gas Turbine Compressor Blade]]></title><link>http://www.practical-metallography.com/directlink.asp?PM110167</link><author></author><description><![CDATA[According to VDI Guideline 3822-3 “this type of corrosion is … caused by the formation of anodic regions of slight local expansion on the electrolyte-wetted surface. The presence of protective layers (passive layers) is a prerequisite for the occurrence of pitting corrosion.” Both requirements are met on gas turbine compressor blades if water condensates on the turbine blades when the machine is at standstill and/or if the compressor temperature remains low enough in a running machine to allow aqueous media to persist, i. e. for the condensation not yet to have evaporated. This is the case with the front row of blades, generally up to stage 6. Passive layers are present on the gas turbine compressor blades, since these parts are generally manufactured from martensitic 12 – 16 % chrome steel, as also the case for steam turbine blades and discussed in detail in other case studies in the book. The failed compressor stator blade in this case study is made of X15Cr13, material no. 1.4024. Pitting corrosion on the front row compressor blades was not uncommon before the introduction of high temperature corrosion protection coatings containing aluminium pigments on these blades. After the introduction of protective coatings, this corrosion mechanism was absent on the coated blades. The coating systems contain aluminium spherules which, given the correct coating method, are in contact with each other to form a continuous electrically conducting layer between the surface of the blade and the protective coating, creating a sacrificial anode resulting in the less noble aluminium – as compared to steel – preferentially corroding to protect the blade material. The damaged part discussed in this case study originates from an older model gas turbine commissioned in 1955 already, having accumulated almost 163 000 hours of operation when the damage was diagnosed. Depending on the type of operation, this represents a period of operation of 15 to 25 years. Such compressor blades were not coated back then.]]></description><pubDate>Thu, 12 Jan 2012 23:00:00 UTC</pubDate></item><item><title><![CDATA[Meeting Diary]]></title><link>http://www.practical-metallography.com/directlink.asp?PM012013</link><author></author><description><![CDATA[]]></description><pubDate>Thu, 12 Jan 2012 23:00:00 UTC</pubDate></item></channel></rss>

