Grain boundaries (GBs) generally exhibit complex structural and compositional features that significantly affect material hardness. Here, we establish a methodology to correlate the local hardness contributions of the GBs with their frequency distribution and their structural and compositional characteristics, using a submicron WC-Co cemented carbide as a model. An exceptional local hardness of (14.68 +/- 0.12) GPa is observed from a 90 degrees WC{0001}/WC{1010} GB, unlike the low contributions from other WC/WC GBs. This is linked to pronounced Cr and Co segregation at this GB, due to Cr affinity at the WC{0001}/Co and WC{1010}/Co phase boundaries and Co infiltration during liquid-phase sintering. Density functional theory results indicate that a large lattice mismatch, strong W-C covalent bonding, and Cr and Co accumulation increase the elastic strain field, resulting in strong atomic distortion near the interface and contributing to exceptional strengthening. Our findings highlight the critical influence of GB complexities on material hardness.

Based on experimental data and extensive experience, magnetic coercivity and saturation moment are traditionally used to estimate the microstructure and quality of cemented carbides, especially in the manufacturing industry. This work demonstrates that predictions of the structural and mechanical properties of manufactured WC-Co elements can be derived in principle from magnetic data alone using an artificial neural network (ANN). A collection of WC-Co pellet samples with a wide variety of powder compositions and processing parameters was produced to cover a wide range of characteristic features for ANN training. The total field distribution, extracted from first-order-reversal-curves, serves as input data for the ANN. Microstructural parameters such as mean grain size and mechanical properties such as hardness and fracture toughness can be derived from the purely magnetic measurements with high accuracy, while the transverse rupture strength shows large errors and cannot be predicted.

The recyclingRecycling of cemented carbides (CC) is an indispensable facet of resource conservation, especially for critical raw materials, signifying its profound environmental, economic, and strategic importance. These complex materials, consisting of refractory carbides embedded in a metallic binder, mainly tungsten carbide and cobaltCobalt, offer versatile recyclingRecycling options. Among these methods, the zinc processZinc process is emerging as the most promising with significant potential regarding energy consumption and quality of products. In this method, zinc reacts with cobaltCobalt binder to form intermetallic phases, resulting in a breakdown of the material's composite structure due to the higher volume of these phases. In the second step, Zn evaporates at high temperatures under vacuum, leaving behind a porous cemented carbide skeleton. By means of crushing, grinding, and sifting, these can be processed into a powder mixture suitable for direct use in the manufacture of new products. While previous research has focused on the formation of Co-Zn phases during the decomposition step, there is a gap in understanding the growth rate of the disintegration layer. Therefore, this study aims to investigate the layer growthLayer growth and the kinetics of the disintegration stage of the zinc processZinc process. By examining these aspects, a deeper understanding of the fundamental mechanisms at play in this method is gained, contributing to further advancements in the recyclingRecycling of cemented carbides.

The magnetic properties of tungsten carbide with cobalt as a binder have long been used in industry to characterize the microstructure of this hard metal. We present bottom-up structural and micromagnetic modeling of WC-Co, from which we obtain coercive fields that compare well to experimental data. Future work will use experimentally obtained microstructure information as input to the structural modeling.

Tungsten heavy alloys are liquid phase sintered two-phase materials in which tungsten grains are embedded in an austenitic base matrix. While the solubility of W in the binder phase is high both at sintering temperature, when the binder phase is liquid, and also after cooling, the solubility of the binder elements in the W phase is very low, but the exact content has been a matter of discussion for a long time. In the present study, laser ablation induction coupled plasma mass spectrometry (LA-ICP-MS) has been employed for analyzing the Ni and Fe content in the W phase of W-Ni-Fe heavy alloys, using specifically prepared low-binder specimens for calibration. It showed that the binder element content is in fact significantly lower than presented in the literature, LA-ICP-MS yield-ing contents of approx. 340 µg/g for Fe and 60 µg/g for Ni.