During abrasive wear of hardmetals, preferential removal of the binder phase is a leading cause of detachment of tungsten carbide grains and increased wear. This work tests the use of a metastable austenitic binder phase that can form deformation induced martensite as a way to improve the abrasion resistance without loss of fracture toughness. The samples are subjected to tests of different severity and the results are evaluated with respect to wear and wear mechanisms. It was found that the wear mechanisms were very similar to those of a cobalt binder reference material and the sample with best performance varied from test to test. Signs of increased resistance to fracture and binder phase removal was seen for the new material, which could explain an increased resistance to wear in the most severe test.

Among several separate challenges, the major one for replacing cobalt in cemented carbides is the difficulty to obtain alternative binder materials with a C-window broad enough to be robustly processed under conventional industrial control on the C content. The C-window is defined as the C content range for which phases that are detrimental to the mechanical properties are avoided. The present paper has two main objectives: first, to show that the processing C-window of Fe-Ni based systems is in fact wider than what thermodynamic equilibrium calculations predict, and that its width can be controlled moderately by tweaking the initial WC grain size and the cooling rate used in the material's processing. Secondly, in case those detrimental phases are not avoided, this work gives insight on how to make their appearance less detrimental for the mechanical properties. The morphology, volume fraction and particle size distribution of the detrimental phases, specifically η6-carbides at low C contents, are investigated to explore desirable combination of hardness and toughness of alternative binder cemented carbides. During this study it was also discovered that in samples with carbon contents below the low-C limit of the C window a carbide with hexagonal lattice known as κ, not commonly seen in cemented carbides, appeared and formed the core of a core-rim structure together with the more common η6-phase. It is believed that the κ-carbide form due to local high concentrations of tungsten during solid state sintering and that it has an impact on the precipitation characteristics of the η6-phase.

Cemented carbides, which are one of the most important composites produced by powder metallurgy, exhibit an excellent performance within metal cutting and rock drilling tools when their hard phase, tungsten carbide, is bound by cobalt. However in recent years, due to health and ethical concerns related to cobalt, there has been a significant focus on designing alternative binders. The martensitic transformation in high-strength steel and its subsequent transformation-induced plasticity effect present a solution to substitute cobalt and improve the overall properties of cemented carbides. However, factors including residual stresses induced by tungsten carbide grains and confined dislocation mean free path significantly affect the martensitic transformation in these composites. In this study, a thermodynamic-based model for the martensitic transformation in steels has been utilized to predict the martensitic start temperature in cemented carbides. The model coupled with a CALPHAD-based approach presents a systematic solution for designing new steel-based binders.

Among several separate challenges, the major one for replacing cobalt in cemented carbides is the difficulty to obtain alternative binder materials witha C-window broad enough to be robustly processed under conventional industrial control on the C content. The C-window is defined as the C contentrange for which phases that are detrimental to the mechanical properties are avoided. The present paper has two main objectives: first, to show that theprocessing C-window of Fe-Ni based systems is in fact wider than what thermodynamic equilibrium calculations predict, and that its width can becontrolled moderately by tweaking the initial WC grain size and the cooling rate used in the material’s processing. Secondly, in case those detrimentalphases are not avoided, this work gives insight on how to make their appearance less detrimental for the mechanical properties. The morphology,volume fraction and particle size distribution of the detrimental phases, specifically η-carbides at low C contents, are investigated to explore desirablecombination of hardness and toughness of alternative binder cemented carbides.During this study it was also discovered that in samples with carbon contents below the low-C limit of the C window a carbide with hexagonallattice known as κ, not commonly seen in cemented carbides, appeared and formed the core of a core-rim structure together with the more common η-phase. It is believed that the κ-carbide form due to local high concentrations of tungsten during solid state sintering and that it has an impact on theprecipitation characteristics of the η-phase.