Al2o3 or al2o3-contained multilayer coatings for silicon nitride cutting tools by physical vapor deposition and methods of making the same

Abstract

The present invention provides an Al2O3 coated Si3N4 cutting tool comprising a Si3N4 based substrate body and a coating layer on the substrate body, wherein the coating layer has at least one Al2O3 coating layer consisting of amorphous Al2O3 or nanocrystalline α-, γ-, or κ-Al2O3. The hard and wear resistant refractory coating is deposited onto the Si3N4-based substrate body by reactive sputtering using bipolar pulsed DMS technique or dual magnetron sputtering method at substrate temperatures of 300-700° C. During the deposition, preferably, the substrate temperature is controlled to achieve the desired crystal structure of the coating. To form amorphous Al2O3 coating on the surface of the substrates, the deposition temperature can be controlled from 300 to 500° C.; on the other hand, to form nanocrystalline α-, γ-, or κ-Al2O3, the deposition temperature can be controlled in the range of 500-700° C. The coated cutting tools of the present invention are suitable for high-speed machining of metals by turning, milling, drilling or by other similar chip-forming machining methods.

Dependencies are inferred from the claim text.