The Effect Of Rare Earth And Copper Addition On The Structure And Properties Of WC-10Co Cemented Carbide

Ultrafine cemented carbides are widely used in aerospace,mechanical processing,petroleum drilling,micro-electronics processing,precision manufacturing and other important fields due to their high strength and high hardness,and have become one of the key development directions of hard materials.How to restrain the abnormal growth of WC grains in sintering process is the difficulty and key to prepare superfine cemented carbide at present.Addition of trace rare earth elements and copper elements can inhibit the growth of WC grains during precipitation.However,most of the current studies focus on the effect of single rare earth or copper addition on the structure and properties of cemented carbides.There are few studies on the effect of different levels of rare earth and its combination with copper on the structure and properties of ultra-fine cemented carbides.WC-10Co-CeO₂-Cu cemented carbide was prepared by atmospheric pressure sintering furnace with WC powder,Co powder,nano CeO₂,micron CeO₂,Cu powder and carbon black as raw materials.The effects of micron CeO₂ and nano CeO₂ addition on the microstructure and mechanical properties of cemented carbide were studied by means of SEM,three-point bending strength tester and three-dimensional profiler.The differences of the effects of micron CeO₂ and nano CeO₂addition on the microstructure and mechanical properties of cemented carbide were compared.It is concluded that 0.4 wt.%nano CeO₂ is the optimum addition of rare earth.On this basis,different contents of Cu are added to explore the influence of different contents of Cu and 0.4wt.%nano CeO₂ on the microstructure and mechanical properties of the alloy.The full text draws the following conclusions:?1?In the range of 0¹.2 wt.%,the addition of micro CeO₂ and nano CeO₂ can refine the grain,and the refinement effect of nano CeO₂ is better than that of micro CeO₂.The average grain size of the alloy decreases first and then increases with the addition of rare earth.The average grain size of WC grain is the smallest when the addition of nano CeO₂ is 0.4 wt%.It is about 410 nm,which verifies the"modification of nano-rare earth".The better addition of CeO₂ is 0.4 wt.%nano CeO₂.Compared with the alloy without CeO₂,the alloy prepared with this addition has 14%higher bending strength,13%higher hardness and better wear resistance.?2?With the addition of 0.4 wt.%nano CeO₂ and 0.4 wt.%Cu,the average grain size of the alloy decreases to 360 nm.The density of the alloy decreases with the increase of Cu.The wear resistance and hardness of the alloy increase first and then decrease with the increase of Cu content.When the addition of more than 0.8 wt.%Cu,the fracture toughness and bending strength of the alloy decrease with the increase of Cu.?3?Based on the variation of the microstructures and mechanical properties of all the alloys with the addition of additives CeO₂ and Cu,a better mixed addition of rare earth CeO₂and Cu was obtained:0.4 wt.%nano CeO₂ and 0.4 wt.%Cu.Under this addition,the microstructures and mechanical properties of the alloys were improved compared with those of the samples without any additives.The average grain size of WC was refined from 530 nm to 360 nm,the hardness was increased by 18%,the fracture toughness was increased by 13%,the bending strength was increased by 17.5%and the wear resistance was also improved significantly.