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This study focuses on preparing two types of cemented carbides: one with Ti elements and the other without, using a stepwise sintering process, primarily evaluating their mechanical properties. The research includes a thorough analysis of microstructure changes and post-wear surface alterations, coupled with assessments of phase composition, element content, relative density, surface hardness, fracture toughness, and wear properties. Results reveal that cemented carbides treated with in-situ surface modification under high-temperature nitrogen atmospheres exhibit exceptional densification. An in-situ hard-phases layer, predominantly TiN or Ti(C, N), is gradually grown on the surface of the WC-Co-Mo-TiNC cemented carbides, enhancing surface hardness and fracture toughness. This technology fortifies the material against indentation, crack expansion, and fracture, significantly improving wear resistance and extending service life. In essence, the in-situ surface modification technology, especially under high-temperature nitrogen atmospheres, emerges as a transformative approach, enhancing mechanical properties and substantially improving wear resistance for prolonged practical applications. [ABSTRACT FROM AUTHOR]

PVD coating is a critical technique to improve the wear resistance and cutting performance of softer carbide substrates. The wear performance of the coating is closely related to the carbide substrate grade, coating parameters, and the coating materials. In this study, a unique carbide grade, 91WC-2TiC-3Co-3Ni-1Mo, has been developed specifically for PVD coating. Two different coatings i.e. TiAlN and AlCrN were successfully deposited with cathodic arc evaporation (CAE) technique on this carbide grade. The microstructure analysis shows good bonding between coating and carbide substrate. The comprehensive sliding wear testing, including reciprocating sliding, ball-on-disc, and micro-scratch testing, has been made to these two coatings. AlCrN coating shows consistently lower coefficient of friction (COF) compared with TiAlN coating in both reciprocating sliding test and ball-on-disc test. In addition, AlCrN coating has consistently higher normal critical loads than TiAlN coating during micro-scratch testing, demonstrating better bonding condition between coating and carbide substrate. [ABSTRACT FROM AUTHOR]

This paper systematically investigated a set of functionally graded WC-TiC-Mo-Co cemented carbides with modified surface layer (called fcc-rich surface layer in this study), which is mainly composed of fcc phases (Ti(CN) and TiN) and WC. Nitridation at liquid phase sintering temperature is the key process making this fcc-rich surface layer. The functionally graded WC-TiC-Mo-Co cemented carbides synthesized in this study show 3 layer structure: the outer layer, i.e. the fcc-rich surface layer; the intermediate layer, which is characterized by abnormally large WC and high Co content; and the inner layer. It was found that TiC is the most critical component for the formation of fcc-rich surface layer. The higher content of TiC results in the thicker fcc-rich outer layer, higher (Ti(CN) and TiN) content in the outer layer, and higher hardness of the fcc-rich outer layer. The formation of this fcc-rich surface layer is mainly due to the nitridation process between Ti and N, which leads to the diffusion of Ti outwards (from the inside of the sample to the surface) and the subsequent migration of liquid cobalt inwards (from surface to the inside of the sample). The three-layer structure developed in this study provides the excellent combination of high wear resistance and high toughness, which is favorable for some applications. [ABSTRACT FROM AUTHOR]