Carbide Gun Drill Coating
For different application, we will recommend suitable grade with excellent performance.
TiN - Coating:
Hardness 2100HV, Gold color
To increase anti-adhesive and wear-resistance
Suitable for stainless steel, chrome steel, nickel steel etc.
AlTiN - Coating:
Hardness 2200HV, Black color
To increase red-hardness and wear-resistance
Suitable for high-temperature alloy, mold steel (NAK80, 738) etc.
Study of accuracy and surface roughness of holes in comparative testing of small diameter gun drills
To cite this article: S V Kirsanov and A S Babaev 2014 / OP Conf. Ser.: Mater. Sci. Eng. 66 012030
The results of industrial tests of gun drills with diameter of 2.05mm with carbide and with steel stems are given. It is shown that gun drills with cemented carbide stem and especially AlTiN coating have a greater resistance and greater accuracy diametrical holes sizes in cimparison to gun drill with steel stem.
In the process of manufacturing fuel injection equipment for diesel engines there is a need for deep holes drilling of small diameters, less than 5mm. The mentioned above holes have high demands of accuracy IT6-9, surface roughness Ra 0.08...1.25 and drill runoff 0.01...0.03mm/100mm. Such small diameters of holes and the specified requirements for them are achieved by the use of tools with certainty based - gun drills. Gun drills with steel (GDSS) or cemented carbide (GDCCS) stems and deposited on the working parts of the wear-resistant coating are mostly used for this purpose nowadays.
GDSS consists of carbide cutting tips, the steel stem and the shank. GDCCS tip and stem are a single cemented carbide rod soldered to the shank, or caribde rod that is both the stem and the shank.
Working parts of GDCCS were deposited with wear-resistant coatings TiN, AlTiN, TiCN (Table 1)
Table 1. Gun drills used in the tests
Results and discussion
37552 holes were drilled by 15 drills during the test. It indicated the high quality of the testing instruments. So, the average limit (until catastrophic wear) tool life of GDCCS without coating was 3128 holes, with TiN coating - 1885 holes, with AlTiN coatings - 2567 holes and TiCN coatings - 3152 holes, and uncoated GDSS - 1770 holes. Moreover, all the GDSS tests were withdrawn due to breakdown while only 5 drills (42%) with cemented carbide stem were destructed. The remaining 7 drills (58%) were not used in the test due to the appearance of burrs at the exit holes and could drill more.
Table 2. The influence of the gun drill type and the kind of wear-resistant coating
1. Tests showed the high quality of gun drills made by Botek.
2. Tool life of GDCCS due to the greater stiffness and strength of 1.5... is 1.8 times higher than the tool life of GDSS.
3. GDCCS with AlTiN coating provide the greatest accuracy and stability of diametrical hole sizes.
4. Wear-resistant coating are reduced holes roughness Ra of 1.5... is 3.0 times than uncoated.