Elastic modulus of compacted powders measured by nanoindentation

Powder injection molding is a method of powder compaction used for manufacturing of various structural components. It is used also for production of light and wear resistant ceramic structural parts with tailored properties. In this application report we show how microindentation can help in characterization of mechanical properties of compacted refractory ceramics.

Powder compaction is a very important process in manufacturing of structural components and other products. It is used for example in pharmaceutical industry to compact powders containing the medicament in order to achieve suitable integrity, hardness, modulus and fracture toughness of tablets. Load bearing structural components are usually manufactured by dry powder compaction, a method where the powder is introduced in a mold, compacted by applying pressure at moderate temperatures and later sintered at elevated temperatures. Dry powder compaction is somewhat similar to injection molding where molten or semi-molten material is injected into a mold where it solidifies but dry powder compaction has the advantage of being able to process also ceramic materials which are otherwise difficult to liquify and inject-mold. Another great advantage of dry powder compaction is that it is fast, wasteless, and it usually requires only very little additional surface treatment. A typical domain of application of dry powder compaction is luxury industry where this method offers reliable and fast production of objects with high hardness and wear resistance together with low weight. An example of a component manufactured by this method are high-end watch cases which are made of zirconia ceramics.
Due to the adjustable process parameters such as pressure and temperature, powder compaction is a flexible process which allows producing of materials with tailored mechanical properties. Materials whose powders were compacted at high pressure will have higher density and therefore higher hardness. On the other hand, materials from powders compacted at lower pressure are expected to have lower hardness due to larger volume of pores. Since the parts produced by powder compaction are relatively small, their mechanical properties have to be measured by appropriate test methods. One of them is instrumented indentation, which allows application of low forces and thus to probe small areas. This way the hardness and elastic modulus can easily be measured and related to material’s density or other manufacturing parameters (pressure, temperature).

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