Performance of alloyed uncoated and CVD-coated carbide tools in dry milling of titanium alloy Ti-6242S

摘要

Many researchers believe that alloyed cemented carbide (W-Ti/Ta)C-Co is not suitable for machining of titanium alloys. However, the result of study reported in this paper shows that the alloyed carbide tools, i.e. alloyed uncoated carbide (W-Ti/Ta/Nb)C-Co and alloyed CVD-coated carbide (W-Ti/Ta/Nb)C-Co + (TiC + Ti/CN + /TiN), have good possibility to use in end milling of titanium alloy Ti-6242S even under extreme dry (green) cutting condition. It is probably due to the grain size of tools' substrate and geometry (off-center ball end mill) and the class of titanium alloy Ti-6242S (α-β). From series of machining trials on the range of cutting speed, V{sub}c between 100 and 125 m/min, f{sub}z 0.15-0.20 mm/tooth, a{sub}a 2-2.5 mm and a{sub}r 8.8 mm using factorial 2{sup}3 with four center points and three replications, it can be concluded that the best performance of the tools is at V{sub}c of 100-110 m/min, f{sub}z 0.15-0.185 mm/tooth and a{sub}a 2-2.25 mm where tool life is ranging from T of 5-15 rnin. Moreover, when those collected data through the trials are analysed using multiple linear regression method, the performance of both alloyed carbide tools can be represented by modified Taylor equations (TV{sub}c{sup}0.30f{sub}z{sup}0.89a{sub}a{sup}0.84 = 74.851) and (TV{sub}c{sup}0.28f{sub}z{sup}0.35a{sub}a{sup}0.57 = 156.192), respectively.