The author made many test, undertook coating and not the hob photograph of coating is compared, cutting tool durability raised 2 ～ 7 times, its economic benefits is very considerable. Gear hob because structure and workmanship are complex, make its price very expensive, manufacturing cost is high. How to improve the life of hob of high-speed steel gear, be treat settlement problem urgently. For this, use physics to enrage deposit law (PVD) , in already besmeared on the gear hob that blade has ground 4 ～ of Fu the TiN of 6 µm, make twice of cutting tool wear extent is reduced, durability rises substantially. After high-speed steel has TiN coat, make 65 ～ 67HRC raises its hardness (surface layer hardness) 83HRC is controlled (1950HV) , exceeded hard alloy (1400 ～ 1800HV) , can make durability of high-speed steel cutting tool raises 2 times above, treatment efficiency raises 50% above. After coating, can raise high-speed steel to fight oxidation temperature, fight caking property to be able to be mixed fight diffuse wear away ability, make the coefficient of friction of steel and steel by 0.
7 reduce 0.
14, attrition force reduces 20% ～ 30% , cutting temperature drops 15% ～ 20% . After hob besmears TiN is ground again, its durability and around knife face coating look is not more also than dropping. Made many test, undertook coating and not the hob photograph of coating is compared, cutting tool durability raised 2 ～ 7 times, its economic benefits is very considerable. CNC Milling