Aluminum oxide coated tool

Abstract

There is provided a tool at least partly coated with at least two refractory layers of which one of the said layers is a fine-grained α-Al2O3-layer which is the top layer along the cutting edge-line and the other a TiCxNyOz- or a ZrCxNy-layer being the top layer on the clearance face. The coated tool exhibits excellent flank and crater wear and high resistance to flaking, particularly when used for machining of low carbon steel and stainless steel. Used cutting edges can easily be identified by the naked eye.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS [0001]This application is a reissue of U.S. Pat. No. 5,861,210, which claims the benefit of priority to Swedish Application No. 9402543-4 filed Jul. 20, 1994. <?insert-end id="INS-S-00001" ?>BACKGROUND OF THE INVENTION[0002]The presently claimed invention relates to an Al2O3-coated cutting tool suitable for machining of metals by turning, milling, drilling or by similar chipforming machining methods.[0003]Modern high productivity chipforming machining of metals requires reliable tools with excellent wear properties. This has so far been achieved by employing a cemented carbide tool body coated with a wear resistant coating. The cemented carbide tool body is generally in the shape of an indexable insert clamped in a tool holder.[0004]The most commonly used wear resistant layers are TiC, TiN, and Al2O3. Both single layer and multilayer coatings are employed. CVD, PVD or similar coating techniques are used for depositing the different laye...

AI Technical Summary

Benefits of technology

[0016]It is further an object of this invention to provide improvements in coated bodies with respect to the tendency of smearing / welding of workpiece material onto the cutting edge, cutting edge flaking resistance, simultaneous high resistance to crater and flank wear and to make “used edge identification” possible.

Problems solved by technology

During, e.g., a turning and cutting operation, the coated tool is worn continuously on its rake face by the formed metal chip which causes crater wear.

The machined workpiece also slides along the clearance face of the tool causing flank wear.

This leads to a diffusion type crater wear on the rake face of the tool.

On the clearance face of the tool, the temperature is significantly lower mainly so that abrasive type wear occurs.

Al2O3-layers on the other hand, wear relatively fast on the clearance face and develop flank wear relatively quickly on that face.

Flank wear influences the machined surface and may therefore limit tool life.

Flaking accelerates tool wear, in particular the flank wear.

Flaking may be the result of inferior coating adhesion or it may be due to the smearing or welding of workpiece material onto the cutting edge and a successive withdrawal of the coating.

Some steels are more difficult to machine than others due to smearing and resulting flaking, for example, stainless steel and low carbon steel.

It is becoming more and more difficult for the machine operator by the naked eye to differentiate between a little used and an unused cutting edge (“edge identification”).

This is particularly difficult if the top layer is Al2O3 which color is dark grey or black.

By mistake, using a used tool cutting edge, e.g., during an unmanned night shift run may cause component rejection or even unwanted production stops.

This method is according to the findings of the present inventors not sufficient to minimize smearing.

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