The Special Coatings for Cutting Tools
It is a important way to increase the cutting tools’ performance by coating .An insulation barrier formed between the cutting tools and chips in the machining process by means of the materials with high heat and wear resistance coated onto the tough tools’ substrate, so as to prevent heat to be transferred to the base and reduce cutting tools’ friction and heat, also play as a role of lubricant to low the friction coefficient between cutting tools and workpiece surface .Thus the coated cutting tools are suitable for dry cutting .for instance ,Al2O3 with very good mechanical properties, red-hardness and chemical stability is the basic composition of the porcelain with Al2O3 as substrate, so it is very good at anti-crater wear ,low thermal-conductivity which is lower as the temperature higher. Consequently ,with these properties ,the heat is prevent from being transferred to the cutting blade and avoid it losing function due to the plastic deformation. Thus ISCAR optimize the oxygen-stability in Al2O3 and increase phase a of heat stability by a-TEC which is MTCVD to improve performance of Al2O3 coating multi-layers.
Generally speaking ,the coating is sorted into two kinds ,one is hard coating with high hardness and good wear-resistance ,such as TiN,TiC,TiCN,TiAlN,Al2O3,CBN,diamond,DLC and nanometer materials etc ;another one is “soft” coating ,this kind of chalcogenide M0S2,WS2 or TaS2 are called friction-reducing coating layer which is capable to low friction coefficient significantly, so also called “self-lubricant coatings”. The tools with this coating are available to make up the lubricant function at a certain extent ,and offset the rise of cutting temperature ,hereby it is very suitable for dry cutting . The grades as IC908 ,IC907,IC903 of ISCAR are belong to hard coating ,they take the utra-fine tungsten carbide as substrate with good anti-mechanic and thermal shock performance, by means of PVD coating of lower friction coefficient to coat TiAlN with high anti-oxidization temperature, the TiAlN file formed in cutting process and help the tools have good anti-oxidization property ,with which the oxidizing temperature is 700℃～800℃that is higher than TiC and TiN coatings’.In high temperature ,TiAlN’s hardness is higher than TiN ,its thermal stability is very good ,meanwhile,a oxidized film formed to reduce friction between tools and chips ,and decrease heat caused greatly .Furthermore ,the thermal conductivity of TiAlN is lower than TiN ,so it can take insulation-heat function and make the tools bear higher temperature .The hardness of PVD-TiAlN coating is equal to TiCN,and TiN ,but its thermal-stability temperature is higher than TiCN and TiN at 1450℃.This kind of TiAlN coating’hardness rises with the increase of Al composition, meanwhile ,it shall have higher high-temperature fracture and wear resistance ,but its oxidizing temperature keeps no change .
In the recent two years ,ISCAR has taken alternate coating with ultra-thin TiN and TiAlN on the tools combined the advantages of TiN,TiAlN and TiNC Coatings ,so they have strong adhesion strength ,high heat and wear resistance, after that ,SUMO-TEC as after-process has been taken on the tools ,so as to improve toughness and wear-resistance, reduce surface friction coefficient ,make lower cutting area temperature, and optimize edge-broken and chip-piling resistance, thereby help customers get longer service life of tools when use them machine most of the materials, and the tools durability is increased by 20%~280%.
