Multilayer coating of a nitride-containing compound and method for producing it

DETAILED DESCRIPTION What is claimed: 1.
A multilayer coated substrate comprising a substrate coated with at least three layers of a nitride-containing compound wherein the composition of each layer is a nonstoichiometric composition which contains at least 2 atomic percent of nitrogen different than the nitrogen contained in an adjacent layer.
2.
The multilayer coated substrate of claim 1 wherein the nitride-containing compound is titanium nitride.
3.
The multilayer coated substrate of claim 1 wherein the nitride-containing compound of one layer is Ti.
sub.
2 N mixed with titanium nitride having an atomic percent of nitrogen of about 40%; the nitride-containing compound of an adjacent layer is nonstoichiometric titanium nitride having an atomic percent of nitrogen of 40% to 55%; and the nitrogen content in one layer has at least 2 atomic percent of nitrogen different than the nitrogen content in an adjacent layer.
4.
The multilayer coated substrate of claim 1 wherein the overall thickness of the coating is from 5 to 30 microns.
5.
The multilayer coated substrate of claim 1 wherein the thickness of each layer is from 0.
1 to 5 microns thick.
6.
The multilayer coated substrate of claim 1 wherein the ratio of the thickness of the layer containing the least amount of nitrogen to the thickness of an adjacent layer containing the higher amount of nitrogen is from 1 to 20.
7.
The multilayer coated substrate of claim 1 wherein at least one layer contains at least one additive from the group comprising titanium, titanium alloys, zirconium and zirconium alloys.
8.
The multilayer coated substrate of claim 7 wherein at least one layer contains at least one element from the group comprising aluminum, vanadium, molybdenum, niobium, iron, chromium and manganese.
9.
The multilayer coated substrate of claim 1 wherein the nonstoichiometric composition of the nitride-containing compound of each layer has an atomic percent of nitrogen from 33% 55% and the nitrogen content in one layer has at least 2 atomic percent of nitrogen different than the nitrogen content in an adjacent layer