Abstract
The powder injection moulding (PIM) technology is lately becoming more and more significant due to complex design possibilities and good repeatability. This technology requires optimization of all steps starting with material and binder, injection, debinding and sintering parameters. Sintering is one of the key links in this technology. The powder injection moulding process is specific as during feedstock injection powder particles mixed into the binder do not come into mechanical contact. Shrinkage during sintering of PIM samples is high. In this work we have analyzed and modeled the sintering process of isotropic PIM samples of Sr-hexaferrite. The Master Sintering Curve (MSC) principle has been applied to analyze sintering of two types of PIM Sr-hexaferrite samples with completely removed binder and only the extraction step of the debinding procedure (thermal debinding proceeding simultaneously with sintering). Influence of the heating rate on resulting sample microstructures has also been analyzed. Influence of the sintering time and temperature was analyzed using three different phenomenological equations.
Highlights
Hard ferrites are used today mainly for the production of different permanent magnetic cores
If we analyze the microstructures of Sr-hexaferrite samples sintered in a dilatometer after thermal debinding, one can note that the microstructures differ in relation to the applied heating rate
If the heating rate is high (15oC/min) the microstrain is high, open and closed porosity is present in the sample, pores have a polygonal shape with an average size 1.5-1.6 μm
Summary
Hard ferrites are used today mainly for the production of different permanent magnetic cores. Sintered ferrite cores are not well suited for additional mechanical treatment such as cutting and grinding to fit the tolerances, and because of that a “near net shape” technology such as PIM (powder injection molding) is an attractive alternative [1, 2]. BaFe12O19 and SrFe12O19 are used most often [3,4,5,6] These ferromagnetic materials can be magnetized along the c-axis. The particles remain oriented during debinding and sintering. Optimization of all steps of the PIM process is very significant This includes selection of a suitable feedstock followed by optimization of debinding and sintering processes
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