Investigation Of Small Energy Multi-impact And Static Fatigue Properties Of WC-Co Cemented Carbides

Cemented carbides,with a series of excellent physical and chemical properties,are widely used in industry,which are called industral tool. The research of cemented carbides tools performance under small energy multi-impact (SEMI) has important significance, because carbide tools are usually used under the condition of small energy attacks. Six kinds of cemeted carbides 114#?115?116#?211#?215# and 218#(produced by Zhuzhou Cemented Carbide Group Corp. LTD, Zhuzhou, China.) were investigated about the SEMI and static fatigue properties. The influence of powder metallurgy defects on the performance of cemented carbide had been discussed. Main conclusion are as follows:(1) The mechanical properties results show:With the same average size of WC grain, impact toughness?bending strength and fracture toughness increase with the rise of Co content,but the hardness decreased. With the same Co content, hardness^ impact toughness and bending strength decreased with the rise of average size of WC grain, but the fracture toughness increased.(2) Two kinds of experimental scheme of SEMI results show:under the same impact energy,the cemented carbide with higher cobalt content presents the longer SEMI life, the cemented carbide with bigger average size of WC grain presents the shorter SEMI life; However, with the same value of ? (the ratio of impact energy to the impact fracture energy at one time), the SEMI life declines with the increase of Co content and average size of WC grain. The cemented carbide with Co content of 18wt% has a higher dynamic fatigue sensitivity and corresponding weak fatigue crack propagation resistance, which means that the high cobalt alloys need a higher safety factor under the service conditions.(3) Three kinds of cemented carbides with different Co content (11 wt%,15wt%. 18wt%) were used to study the static fatigue properties, results show:Under the same static stress, the cemented carbide with higher cobalt content presents the longer static fatigue life, However, with the same value of 0 (the ratio of static stress to bending strength), the static fatigue life of the three alloys declines with the increase of Co content. The cemented carbide with Co content of 11wt% has a lower dynamic fatigue and static fatigue sensitivity and corresponding better fatigue crack propagation resistance. Static fatigue life of notched specimens is lower than that of smooth specimens. When the 0 is 0.8, the fatigue life ratio of the three smooth specimens and three notched specimens (with Co content of 18wt%,15wt% and llwt%) is approximately 1:2:7 and 1:1:2 respectively, which exhibits that the pre-notched specimens cover the defects of cemented carbides.(4) Fracture of hardmetals bearing low energy (SEMI and static fatigue) results from the growth and connection of holes (or coarse WC) and micro-crack which is internal defects or formed in the experimental process.