Is PVD the BEST coating for all applications?
PVD is not the “BEST” for all metal cutting applications, but it can get the job done when applied properly, so I am going to give you a refresher tutorial to help you in your decision making process. Those of us who cut metal every day know that coatings are still the hottest technology in the cutting tool industry and have been for decades. The next big thing to come along will undoubtedly be a new coating technology and process. Until then...
Basically,
there are 3 types of COATING PROCESSES for cutting tools- PVD, CVD, MT-CVD. Combinations of them are not as common as
they once were, but a combination of the compounds used in the coating process
is expanding. Compounds like TIN,
Aluminum Oxide, TIALN, etc. All coatings have advantages and disadvantages,
which can be leveraged in the application of cutting tools.
PVD coated grades are recommended for sharp, tough cutting edges, and cutting in smearing materials. Such applications are widespread and include carbide and HSS end mills, drills, taps, reamers, and hobbs and broaches. Because of PVD’s lubricity and smooth surface, a majority of grades for grooving, threading, drilling and milling, lend themselves to the use of PVD coatings. PVD insert grades are also extensively used for finishing applications and as the central insert grade in drilling.
PVD coatings
generally have the least abrasion resistance, so for Cast Iron it is less than ideal
for carbide applications. I wouldn’t expect it to perform above other coatings
in that use. Its low process temperature allows it to be used on virtually all HSS
cutting tools successfully.
CVD coated grades
are a good choice in a wide range of applications where wear resistance is
important, and the edge condition is honed, such as face milling and turning. With superior crater wear resistance offered
by thick CVD alumina coatings, they are properly applied to the general turning
Steels, Cast Irons, and Stainless Steels.
In thinner coatings, you will find CVD used for milling grades in ISO P,
ISO M, ISO K. For drilling, CVD grades are often used in the peripheral
insert.
MT-CVD
coating layers are applied by state of the art medium temperature chemical
vapor deposition furnaces that can yield a CVD coating hardness for wear and
crater resistance yet the coating is real tough and smooth. Most importantly, substrate properties and
edge strengths are fully retained. These substrate properties impart high
resistance to both plastic deformation and edge chipping, making the grade
ideal for machining tough cutting ductile Irons at normal and above cutting
speeds.
MT-CVD
(Medium Temp) is the newest and most widely desired coatings. That
is what all the largest manufacturers are moving toward for most applications
of carbide. It has the most advantages and the least disadvantages it is also
suited for multi layering. Unfortunately, it greatly complicates the selection,
obsolescence, and application of cutting tools.
The best
advice that I can give anyone using carbide inserts; “the best coated insert in
the world, used improperly, is a waste of money. It’s a strange relationship,
found almost nowhere else”.
There is
more value in HOW a tool is applied,
than the value in the cost of the tool.
Some hones
and coatings can make up for the cutting conditions being poorly applied.
PVD is very
good for this, resulting in a good tooling value, besides its other advantages.
Call the TMX Cutting Tool Team @
508-653-8897 for advice with your Indexable and Round Tool needs.
