The polishing cloth should be moist, not wet. The amount of lubricant has to be adjusted correctly to get the best result. Hard materials require less lubricant but higher amounts of abrasive, due to faster wear. Generally, it can be said that soft materials require high amounts of lubricant to avoid damage, but only small amounts of abrasive as there is very little wear on the abrasive. This may include thin lubricants with high cooling and low lubrication effect, special lubricants for polishing of soft and ductile materials, alcohol-based or water-based, etc.ĭepending on the type of material and the grinding/polishing disk used for preparation, the amounts of lubrication and cooling have to be balanced. Lubricant Depending on the type of material and the preparation stage, different lubricants combine levels of lubricating and cooling levels and liquid characteristics. The combination of cloths with low resilience and hard specimens requires a larger amount of abrasive than cloths with high resilience and softer specimens, because the abrasive particles wear faster. The amount of abrasive applied depends on the grinding/polishing surface and the hardness of the specimen. Never change to softer abrasives - this might lead to preparation artifacts. Colloidal silica is used to produce a scratch-free finish in oxide polishing steps In general, the abrasive must have a hardness of 2.5 to 3.0 times the hardness of the material to be prepared. It was also extensively used as a polishing medium, but since the introduction of diamond products for this purpose, it has largely lost its usefulness in this application. It is mainly used for the preparation of ferrous metals. Aluminium oxide, with a hardness of about 2,000 HV, is primarily used as an abrasive in grinding stones. Silicon carbide, SIC, with a hardness of about 2,500 HV, is a widely used abrasive for grinding papers for mainly non-ferrous metals. Tests have shown that the high material removal, together with a shallow scratch depth, is obtained because of the many small cutting edges of polycrystalline diamonds. Different types of diamonds are available. That means it can easily cut through all materials and phases. Diamonds are one of the hardest known materials, as they have a hardness of approximately 8,000 HV. The removal rate in grinding and polishing is closely related to the abrasives used. A prerequisite is to have an idea of how a ductile or brittle material will perform. Place the material on the Y-axis according to any previous experience. Unlike hardness, ductility is not easily defined in precise numbers.ģ. Move up or down, depending on the ductility of the material. The shape of the Metalogram results from soft materials generally being more ductile and hard materials usually being more brittle.Ģ. The values are not shown in a linear progression, because the variety of preparation methods for softer materials is greater than for hard ones. The X-axis represents the hardness in Vickers (HV). This property expresses how the material responds to mechanical abrasion. Ductility: The ability of a material to deform plastically is important for grinding and polishing.Hardness: T he easiest attribute to measure but is not sufficient information about a material to find the correct preparation method.How to select a preparation method The Metalogram displays materials according to specific physical properties: hardness and ductility. Solving materialography's biggest challenges How Automation drives Value for Materialography Grinding stones and diamond grinding discsģ ways to improve your process when cutting large piecesĦ ways to improve the speed and efficiency of your cuttingħ ways to optimize cutting liquid for optimal sectioning
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