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The structure and properties of tungsten carbide hardmetal with 8 wt.% Co produced by cold and hot isostatic pressing with the same starting powder mixture and conventional initial pressing of billets in metal dies were studied. The first batch of the samples was prepared by vacuum sintering of the pressed billets. The second batch was prepared by vacuum sintering followed by hot isostatic pressing of the billets at 5 MPa. The third batch was prepared by hot isostatic pressing at 200 MPa followed by vacuum sintering. The sintered samples had a density of 14.57 g/cm 3 in batch 1, 14.60 g/cm 3 in batch 2, and 14.63 g/cm 3 in batch 3. Microstructural analysis showed that cold isostatic pressing promoted more homogeneous and finer structure. According to the coercive force determination and structural analysis performed with scanning electron microscopy and X-ray diffraction, the average size of carbide grains was 1.315 m for the samples in batch 1, 1.396 μm in batch 2, and 1.062 m in batch 3. Determination of residual stresses indicated that they were compressive in both phases (WC and Co) of the batch 3 samples and tensile for the batch 1 and 2 samples. The average values of measured Rockwell hardness were 88, 87, and 90 HRA for the samples in batches 1, 2, and 3. Mechanical tests of the samples indicated that the bending strength and fracture toughness were 1820

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An effect of microstructure on magnetoresistive properties of manganite ceramics (La0.65Sr0.35)0.8Mn1.2O3±Δ with superstoichiometric manganese has been studied after sintering in the temperature range of 800–1500 °C. Increase in sintering temperature to 1400 °C, an enormous growth of grains, densification of material, and rise in magnetoresistance peak from 1% to 4.8% are observed. At the same time, sintering at 1500 °C leads to a sharp increase in the grain size more than 100 μm, release of excess manganese on grain boundaries, and almost two times magnetoresistance peak rise. We propose that such radical changes are due to the presence of superstoichiometric manganese which plays a crucial role in the formation of ceramics microstructure and properties.

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