Structure news · # 19 · December 2014 Structure news Comparing Different Preparation Techniques for the Characterisation of Niobium carbides Authors: www.struers.com In this issue Comparing different preparation techniques of Niobium carbides1 Redesigning ductile plane grinding surfaces2-3 e-Seminar Q & A 4 e-Seminars 2015 5 M. Scheibe, S. Binkowski, S. Benemann, R. Saliwan-Neumann This article was first published by BAM Bundesanstalt für Materialforschung und -prüfung, DE-12200 Berlin, Germany Abstract Electronic imaging analytic methods like SEM-EDX, FESM or EBSD enable with the first characterization a definite and direct insight on composition, components and other characteristics of a sample. Especially for new materials these characteristics are often unknown and micro structures may be very fine. Materialographic steps like cutting, grinding and polishing are still necessary. Based on results of the above mentioned methods classic metallographic preparation steps can be aligned to the characteristics of new materials. So for non-bond and metal bond NbC’s a complete and descriptive structure analysis is also possible with “classic” metallographic methods. You can read the full article here: English version http://www.struers.com/article-niobium_carbides_EN German version http://www.struers.com/article-niobium_carbides_DE Structure news is a quarterly newsletter from Struers, the world leader in materialography. The newsletter provides you with up-to-date information on materialography, applications and new innovative products. For more information about our products, please contact your local sales representative, listed on www.struers.com/distributors To subscribe to Structure news, please go to our website www.struers.com/structurenews 1 Structure news · # 19 · December 2014 Structure news Redesigning ductile plane grinding surfaces Author: Thomas Nørbygaard, Ph.D., R&D Department, Struers A/S Creating an abrasive surface for metallographic plane grinding of ductile materials is not an easy task. Ever since the launch of the MD-Piano, Struers successful diamond disc for hard materials grinding, there has been increasing demand for an equally useful disc for ductile materials: A hard surface with integrated abrasives, durable and designed for multiple uses, giving extremely flat surfaces and finally providing an alternative to the well-known but somewhat tedious SiC Paper/Foil solution. Many attempts have been made to create a general plane grinding solution for ductile materials. However, it has not been easy to find a solution that can really compete with SiC Paper/ Foil in a broad sense. First and foremost because “ductile materials” are very far from being a homogenous group and trying to encompass all these different materials requires prioritizing opposing requirements for the surface. Aluminium - Silicon Cast Grinding Step PG FG Surface MD-Molto MD-Largo Abra- Type sive Size Diamond Diamond #220 9 μm Suspension / Lubricant Water DiaPro Allegro/ Largo Rpm 300 150 Force (N)/ specimen 25 30 Time (min) Until plane 4 Step DP OP Surface MD-Mol MD-Chem Abra- Type sive Size Diamond Collodial Silica 3 μm 0.04 μm Suspension / Lubricant DiaPro Mol R OP-U NonDry Rpm 150 150 Force (N)/ specimen 25 15 Time (min) 3 1 This approach eventually leads to a mediocre surface that may be applicable for a big range of target materials, but is not really great for any of them. Instead we started focusing on the key difficulties and requirements for smaller material groups: MD-Molto – The grinding disc for aluminum As is well known, it is generally easy to grind aluminium and aluminium alloys. SiC Paper/Foil is highly efficient on aluminium and just about any abrasive surface, (including those designed for ferrous metals and ceramics), is able to grind aluminium – usually with decent to good removal rates as well. Most tools, however, are not up to this task for long. Huge, aggregated aluminium chips eventually become stuck on the tool surface or cover the abrasives, impeding further grinding or causing extreme wear. Surfaces that might last for hours when grinding steels will suddenly wear down in a few minutes when grinding aluminium. Struers new aluminium disc is based on coated diamonds, which gives the most durable combination of wear properties and retention of abrasives. It features filler grains to stabilize the resin matrix, special additives added to minimize chip clogging and finally a new massive pattern designed for chip clearance and longevity. The removal rate of the disc is modest (compared to other, more aggressive surfaces), but still sufficiently high to allow a plane grinding operation in about one minute using low grinding forces. The disc is self-dressing, gives constant performance throughout, and with a disc life of 100 + operations, plane grinding of aluminium has never been easier or more convenient. Polishing Fig. 1: Aluminium-silicon cast, refined, bright field, 500x. 2 Structure news Structure news · # 19 · December 2014 MD-Mezzo – The grinding disc for titanium alloys Developing a plane grinding disc for titanium called for a completely different focus. Here the difficulty lies in raising the removal rate to tolerable levels, as titanium resists deformation Preparation Method Grinding Step PG FG SurfaceMD-Mezzo MD-Largo Abrasive Type Size DiamondDiamond #220 9 μm Suspension/ Water Lubricant DiaPro Allegro/Largo rpm300 150 F orce [N]/ specimen 40 * 30 Time (min) Until Plane 5 and abrasive processing very efficiently. SiC Paper/Foil is the standard tool of choice for titanium, but even these surfaces struggle, requiring many minutes and multiple paper shifts, when plane grinding massive titanium specimens. In the new multilayer surface for titanium we find that once again coated diamonds are the superior choice of abrasive to keep a constant, high performance. Removal is boosted by a combination of relative high grinding force, a customized resin matrix ingredient and an aggressive pattern. This allows for average removal rates beyond that of SiC Paper/Foil, combined with the superior flatness you only get from a hard surface. Despite the rough grinding conditions, disc life is substantial allowing for 100 + plane grinding operations of solid titanium alloy specimens. With two new discs launched in 2014 we hope to help users all over the world improve their plane grinding procedures for aluminium and titanium alloys. Polishing Step OP SurfaceMD-Chem Abrasive Type Size Suspension / Lubricant Collodial Silica 0.04 μm OP-S** rpm150 Force [N]/ specimen 30 per sample Time (min) 5 *** Table 1 shows a general, automatic preparation method for titanium and its alloys with 6 unmounted samples, 30 mm dia. clamped in a holder. Please be aware that the polishing time can vary depending on the purity of the titanium and the area of the sample surface. * Decrease to 25 N to aviod pencil shapes in single sample preparation. ** Mix 90 ml OP-S with 10 ml H2O2 (30%). *** T he polishing time depends on the sample area. Very large samples require more polishing time than small ones. Fig. 2: Titanium alloy-Ti6Al5V, polarized, 200x. 3 Structure news · # 19 · December 2014 Structure news Struers e-Seminar Q&As by Birgitte Nielsen, Application Specialist, Struers A/S Q: Are there any way out for clay ore? A: Preparing water sensitive minerals is a delicate matter as both equipment and consumables have to be suitable for operating “water-free”. Water free cutting fluid as well as alcohol based lubricant for grinding and polishing processes are available from Struers. Q: Impregnation of soils and loose sediments. Which type of resins are best used for impregnating soils and loose sediments generally? A: It is extremely important that the material/soil is absolutely degreased and dry before mounting! And the best mounting method to get a good impregnation and adhesion is to use vacuum impregnation with an epoxy resin. One method to clean material before mounting is the “Soxhlet Extractor”[1]. Q: What is the refraction index for the UV curable adhesive you mentioned? A: The epoxy ideally has an refraction index of 1.54. Struers EpoFix is 1.58 and EpoSpeed 20 (UV curable) is 1.56. [1] A Soxhlet extractor is a piece of laboratory apparatus invented in 1879 by Franz von Soxhlet. It was originally designed for the extraction of a lipid from a solid material. However, a Soxhlet extractor is not limited to the extraction of lipids. Typically, a Soxhlet extraction is only required where the desired compound has a limited solubility in a solvent, and the impurity is insoluble in that solvent. If the desired compound has a significant solubility in a solvent then a simple filtration can be used to separate the compound from the insoluble substance. 4 Structure news · # 19 · December 2014 Structure news e-Seminars 2015 Struers conducts e-Seminars every month. The e-Seminars cover various topics related to the materialographic world and give you a chance to ask the Struers metallographer questions on the covered topic. If you are unable to participate in an e-Seminar, you can register and see recordings of previous e-Seminars. e-Seminar on Preparation of Titanium 27/1 e-Seminar on Materialographic etching 3/2 e-Seminar on Mineralographic processes - New “Mineralogram” 10/3 e-Seminar on Electrochemical preparation 14/4 e-Seminar on Welding inspection 12/5 e-Seminar on Clamping 23/6 e-Seminar on Materialographic troubleshooting 8/9 e-Seminar on On-site preparation 13/10 e-Seminar on Hot mounting 10/11 5
© Copyright 2024