The Structure and Mechanical Properties of WC–8 wt.% Co Hardmetal Produced by Cold and Hot Isostatic Pressing

• Published in: Powder metallurgy and metal ceramics 2022-05, Vol.61 (1-2), p.9-17
• Main Authors: Akimov, G. Ya, Andreev, I. V., Sheremet, V. I., Trosnikova, I. Yu, Loboda, P. I., Kosenchuk, T. O.
• Format: Article
• Language: English
• Subjects: Bend strength; Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Coercivity; Cold isostatic pressing; Cold pressing; Composites; Compressive properties; Fracture toughness; Glass; Hardness; Heat treating; Hot isostatic pressing; Materials Science; Mechanical properties; Mechanical tests; Metallic Materials; Microstructural analysis; Natural Materials; Residual stress; Rockwell hardness; Sintering; Sintering (powder metallurgy); Structural analysis; Tungsten carbide; Vacuum sintering
• ISSN: 1068-1302; 1573-9066
• DOI: 10.1007/s11106-022-00290-0

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/cm3 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 μm for the samples in batch 1, 1.396 μm in batch 2, and 1.062 μm 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 + 110 MPa and 18.9 + 1.2 MPa · m 1/2 for the samples in batch 1, 2030 + 130 MPa and 18.2 + 1.1 MPa · m 1/2 in batch 2, and 2040 + 120 MPa and 18.6 + + 1.2 MPa · m 1/2 in batch 3. The high mechanical properties of the hardmetal are determined by structural variations and change from tensile to compressive residual stresses in the batch 3 samples.