It is the old things to use the stone or copper alloys as the materials of cutting tools .In the middle of century 18th ,after the industrial revolution ,the cutting tools were made of carbon tool steel,which composition is similar to current grade T10 and T12.The carbon tool steel with comparatively high hardness ,its cutting edge is ground to be very sharp but only available to bear the cutting temperature as 200～250℃,so ,its working efficiency is very low due to cutting speed is only capable at 5～8 m/min.In the year of 1865,Robert Mushet from Britain invented alloy tool steel with grade 9CrSi,CrWMn etc which is available to bear the cutting temperature as 350 ℃ and reach cutting speed at 8~12m/min.With the widely use of machine to produce, the requirement for working efficiency is higher and higher,and the two steels mentioned above is unavailable to catch it .In 1898,American mechanism engineer F.W Taylor and metallurgy engineer M.White invented high speed steel with composition as C:0.67%,W18.91%,Cr 5.47%,Mn 0.11%,V0.29%,and rest as Fe at that time. It is capable to sustain 550~600℃cutting temperature and cut common steel with speed at 25~30m/min.The working efficiency and cutting speed of high-speed steel are 4 and 2.5 times than carbon tool steel and alloy tool steel respectively. Since middle of century 19 to the early of 20th ,the cutting level was leaped by the high-speed steel, meanwhile ,also with help of it ,American machine-manufacture industry had developed very quickly ,and made tremendous economic benefits .
With the development of our life and improvement of the producing capability ,the high-speed steel is unavailable to catch the requirement of high working-efficiency and machining quality .People searched for a new material with high performance .In the mid-1920s to early 1930s,the WC-Co and WC-TiC-Co hardmetals were emerged, meanwhile they were widely used generally due to its high hardness as HRA89~93,capability to bear high cutting heat range from 800~900℃,especially its cutting speed is 3~5 times than high-speed steel.Durring in the work war II ,the tungsten carbide tools were used partially in America,Britain,Soviet Union and Germany for the requirements of mass and high efficiency to produce weapons .After the war ,the tungsten carbide tools were introduced to our country from Soviet Union ,after that ,they were widely used and produced by ourselves too.Durring in the term after-mid-20th ,the tungsten carbide tools played more and more important roles in machining work owing to the higher performance of workpiece, output and categories of products increased gradually, higher requirement for the tolerance ,and more complication and diversification of the workpieces’ materials and structures. In addition ,the tungsten carbide also was developed ,as the new grades emerged and its performance is higher and higher .However ,the tungsten carbide is impossible to replace high-speed steel completely as its toughness is too low and it very fragile, so its machinability is far below the high-speed steel, consequently ,at first ,it is only used as turning and milling inserts, later extended to other tools .For this reason, high-speed steel is available to be processed into various tools, which still occupy big part of the market. In the meantime, the high-speed steel has been developed a lot of new grades and its performance has been improved greatly. Now, the high-speed steel and tungsten carbide are the two main materials of the tools, in which tungsten carbide is slightly more than half. Only after half a century, nobody can expect the tungsten carbide occupies so big market .It is really out of our expectation.
Actually ,tungsten carbide tools are incapable to catch the modern requirements for high-precision machining on super-hard workpieces,so the new materials were emerged .In 1930s,the Al2O3 porcelain was emerged ,and later Si3N4 porcelain got out too. In 1950s to 1960s ,the PCBN and PCD were invented ,their hardness is much higher than other materials. The hardness of porcelain is slightly higher than tungsten carbide ,but its toughness and machinability are far below the tungsten carbide.
