Study On The Microstructure And Properties Of Co-Fe-Ni Composite Binder Phase Ultrafine Cemented Carbide

As the most widely used binder in cemented carbide production,cobalt has the problems of scarce resources and high cost.Fe and Ni can be used as alternative binders because of their similar properties with Co.Ni is helpful to improve the corrosion resistance due to its passivation characteristics.Fe helps to refine WC grains and improve wear resistance.By adjusting and optimizing the composition and structure of Co-Fe-Ni composite binder phase,the specific performance requirements of corrosion resistance and wear resistance of cemented carbide under different working conditions are met.Since the harmful phases of carbon deficiency and carbon enrichment are easy to occur in the preparation of cemented carbide by using composite binder,the carbon window interval is determined by the phase diagram calculation method in this paper,and the carbon balanced cemented carbide is prepared scientifically and efficiently.The influence of the composition ratio of Co-Fe-Ni binder phase on the distribution of binder phase and the shape and size of WC grain were studied,and the relationship between the binder phase and the physical and mechanical properties of the alloy was analyzed.At the same time,the corrosion resistance and wear mechanism of cemented carbide were explored.The main research contents and conclusions are as follows:（1）The microstructure and physical and mechanical properties of WC-10（Co-Fe-Ni）with different binder phase components were studied.The results show that the increase of Fe/Ni ratio in Co-Fe-Ni binder phase refines the grain size of WC and binder phase,and make the WC gap filled in binder phase metal sintering stage insufficient,resulting in uneven distribution of binder phase,increased hardness and reduced flexural strength.The increase of Co content in binder phase is conducive to improve the uniformity of binder phase and improve the comprehensive mechanical properties of the alloy.The main factors affecting the mechanical properties of the alloy are the distribution of binder phase,WC grain size and solid solution strengthening of binder phase.In the range of composition studied,when the Fe/Ni ratio in the binder phase of WC-10（Co-Fe-Ni）cemented carbide is 3:7 and the Co content is 7 wt.%,the cemented carbide can obtain excellent comprehensive mechanical properties,which is similar to that of typical WC-Co cemented carbide.（2）The corrosion behavior of WC-10（Co-Fe-Ni）with different binder phase components in 3.5 wt.%Na Cl solution was investigated by standard electrochemical method.The results show that cemented carbides are mainly corroded by binder phase metal in neutral Na Cl solution,the corrosion form is pitting corrosion,and the corrosion process is preferential dissolution of binder phase metal.With the extension of immersion corrosion time,a passive film is formed on the alloy surface to slow down the anodic corrosion.The corrosion resistance of WC-10Co cemented carbide is lower than that of WC-10（Co-Fe-Ni）cemented carbide.Due to local acidification on the surface,WC-10Co alloy is difficult to form passive film and slow down the dissolution of binder.WC-10（Co-Fe-Ni）alloy can improve the corrosion resistance by reducing the ratio of Fe/Ni and Co content of binder phase.Under the immersion corrosion of neutral Na Cl solution,the corrosion resistance of WC-10（Co-Fe-Ni）cemented carbide is the best when the Fe/Ni ratio is 3:7 and the Co content is 3 wt.%.（3）The wear behavior of WC-10（Co-Fe-Ni）with different binder phases was studied by ball-surface reciprocating sliding dry friction experiment.The results show that the improvement of wear resistance of the alloy is mainly due to the improvement of hardness and the strength of binder phase.The increase of Fe/Ni ratio of binder phase improves the hardness of the alloy and reduces the wear rate.The increase of Co content makes the binder phase more prone to slip stacking fault,and the deformation hardening effect reduces the wear.When Si₃N₄ is used as auxiliary material,the wear resistance of WC-10（Co-Fe-Ni）cemented carbide is the best when the Fe/Ni ratio is 7:3 and the Co content is 7 wt.%.