Effects Of Ru And Re On Microstructure And Properties Of WC-15Co Cemented Carbides

Cemented carbide was a ceramic based metal composite material prepared by powder metallurgy using refractory metal carbides as the hard phase and transition metals as the bonding phase,which was widely used in the field of cutting tool materials.For the last few years,since the rapid development of upper level manufacturing industry,people had put forward new requirements for the performance of cutting materials.Therefore,element doping was widely used to improve the general performance of cemented carbide.WC-15Co cemented carbide with a gradient structure including a thin cubic carbides free layer on the surface was selected as the research object in this study,and the effects of ruthenium（Ru）and rhenium（Re）on the microstructure and properties of the cemented carbide were researched.The high temperature hardness and oxidation resistance of WC-15Co cemented carbides were mainly studied.Besides,the relevant mechanism was investigateded.Through comprehensive comparison,the gradient cemented carbide with the best doping element content was obtained.The results indicated that the addition of Ru could effectively prevented the WC grain from growing,thus resulted in the less number of abnormally grown WC grains.When the content range of Re was 0-5.0 wt.%,the average WC grain size of the alloy changed from1.88 to 1.39μm.The Ru additive resulted in the formation ofβlayer on the surface detachment,and the thickness increased from 24.1 to 35.5μm.When the amount of Ru was3.0 wt.%,the room-temperature hardness,high-temperature hardness,transverse rupture strength（TRS）,and fracture toughness(K_1C)of the cemented carbides reached their optimal values at the same time.When the content of Ru exceeded 3.0 wt.%,graphite phase appeared inside the alloy,and the hardness,TRS,K_1C,and other properties of the alloy decreased to varying degrees.Meanwhile,compared to room-temperature hardness,the hardness reduction of Ru-containing alloys at high temperature environment was significantly lower than that of ordinary alloys.Thus,Ru could effectively improve the high-temperature hardness and high-temperature oxidation resistance of alloys.Re had a significant inhibiting effect on WC grain growth in t cemented carbides.When the content range of Re was 0-7.5 wt.%,the average WC grain size of the alloy changed from1.88 to 1.13μm.At the same time,the addition of Re could effectively reduce the number of abnormally grown WC grains.The addition of Re did not change the thermodynamic and kinetic formation conditions ofβlayer on the surface detachment,and theβlayer hardly changed with the content of Re.When the content of Re in the alloy was 4.5 wt.%,its bending strength and fracture toughness simultaneously reached a peak,but excessive Re could cause a decrease in both values of alloy.This was due to the fact that Re was very easy to form a high hardness and high density TCP inside the alloy,bringing with the reduction of the mechanical properties of the cemented carbides.Re owned good high-temperature performance,and the reduction of high-temperature hardness for alloy after doping Re was also significantly lower than that of ordinary alloys.Its high-temperature oxidation resistance also increased with the increase of the amount of Re.By comparing the changes in high-temperature properties of Ru-containing alloys and Re-containing alloys,it is found that the high-temperature hardness and high-temperature oxidation resistance of Re-containing alloys were better than those of Ru-containing alloys.Therefore,Re was significantly superior to Ru in improving the high-temperature performance of cemented carbide.