WO2024180128A1

WO2024180128A1 - A coated cutting tool

Info

Publication number: WO2024180128A1
Application number: PCT/EP2024/055088
Authority: WO
Inventors: Ludvig LANDÄLV
Original assignee: Ab Sandvik Coromant
Priority date: 2023-02-28
Filing date: 2024-02-28
Publication date: 2024-09-06

Abstract

The present invention relates to a coated cutting tool (1) for metal machining comprising a cemented carbide substrate body (5) and a coating (6) comprising a layer of a metal nitride, there is an uppermost part of the cemented carbide substrate body (5) wherein there are WC grains comprising an uppermost WC interface to the coating (6) and wherein there is a binder phase comprising an uppermost binder phase interface to the coating (6), the WC grains comprising an uppermost WC interface to the coating (6) has an uppermost zone adjacent to the coating (6) which, in addition to W and C, comprises N and one or more of Ti, Cr, Zr, Nb, Mo and V, the uppermost zone being from 1.5 to 8 nm, said uppermost zone of the WC grains, adjacent to the coating (6), comprises <0.6 at% of any noble gas element or combination of noble gas elements.

Description

A coated cutting tool

The present invention relates to a coated cutting tool for metal machining wherein there is a cemented carbide substrate with a coating comprising a metal nitride layer.

Introduction

In metal machining operations cutting tools, such as inserts, are used. A cutting tool generally has at least one rake face and at least one flank face. A cutting edge is present where a rake face and flank face meet. Metal machining operations include, for example, turning, milling, and drilling. As examples of cutting tools are cutting inserts, endmills and drills.

In order to provide a long tool life, a cutting tool should have high resistance against different types of wear. In order to increase wear resistance of a cutting tool various types of wear resistant coatings are known in the art. Metal nitride layers are commonly used in such wear resistant coatings. Especially metal nitrides deposited in a physical vapour deposition process. Examples of metal nitrides are nitrides of one or more of titanium, chromium and zirconium, sometimes in combination with aluminium and/or silicon. Monolayers of metal nitrides or multilayers of alternating sublayers of different metal nitrides can be used.

Cemented carbide is commonly used as a substrate material in a coated cutting tool as discussed above. Cemented carbide comprises hard constituents of tungsten carbide grains in a binder phase. The binder phase is usually made of cobalt, although other elements like iron and nickel may be used in binder compositions. There may also be further hard constituent grains of metal carbides or carbonitrides present in the cemented carbide.

The influence of the properties of the interface between a cemented carbide substrate and a metal nitride layer to metal cutting performance is complex. One aspect can be referred to as the adhesion between a metal nitride layer and a cemented carbide substrate. In order to provide high performance of the cutting tool the adhesion must be sufficiently high avoiding that the coating flakes off during use of the cutting tool. The adhesion of a metal nitride to a substrate may be influenced by, for example, the elemental composition of the metal nitride, the residual stress level in the metal nitride layer as well as at the surface of the cemented carbide, the roughness of the substrate surface and the general properties of the interface between the cemented carbide and the metal nitride layer.

Cutting tools for metal machining are subjected to different types of wear during use. Different metal machining operations affect a coated cutting tool in different ways. Turning, for example, is a continuous metal machining operation while milling is more intermittent in nature.

One type of wear which is of high importance in turning operations is flank wear which takes place on a flank face of the cutting edge, mainly from an abrasive wear mechanism. The flank face is subjected to workpiece movement and too much flank wear will lead to poor surface quality of the workpiece, inaccuracy in the cutting process and increased friction in the cutting process.

In milling the thermal and mechanical load vary over time. Thermal load induces thermal tensions which may lead to so-called thermal cracks, herein referred to as "comb cracks", in a coating, while the later may cause fatigue in the cutting edge leading to chipping, i.e., small fragments of the cutting edge loosening from the rest of the substrate. Thus, common wear types of a coated cutting tool in milling are cracking and chipping. A high comb crack resistance is thus of importance for tool lifetime in, for example, a milling operation. A high edge line toughness is, furthermore, an important property of a cutting tool in milling operations.

Machining of ISO-S materials, such as titanium and heat resistant super alloys (HRSA), puts special demands on the cutting tool. The ISO-S materials have, for example, poor heat conductivity which generates high temperatures during machining creating wear. Also, the tendency of strong work hardening of the ISO-S materials lead to risk of built up edge on the cutting tool which effects the quality of the workpiece such as poor surface finish. Furthermore, when machining titanium problems due to the high reactivity of titanium may occur especially at the high temperatures created during machining. Typically smearing is connected to the formation of built up edge. Also when machining ISO-M materials, i.e., stainless steel, adhesive wear is an important wear mechanism, especially in milling operations. Adhesive wear, or smearing, is characterized in that during the cutting process of sticky materials, such as stainless steel, workpiece material is smeared over, and adhered to, the cutting edge creating a layer of material which may form a so called built-up edge. Flaking of the coating is a common problem in connection to adhesive wear.

The properties of an interface between a cemented carbide substrate and a coating thereon may influence not only flaking behaviour as discussed above but also other types of wear, such as flank wear.

There is a continuing demand for wear resistant coated cutting tools with improved tool life.

Object of the invention

There is an object of the present invention to provide a coated cutting tool for metal machining which has a long tool life in metal cutting operations.

The invention

It has now been provided a coated cutting tool for metal machining which, at least, shows high flank wear resistance and/or high flaking resistance in metal cutting operations in one or more of ISO-S and ISO-M workpiece materials. Preferably, the coated cutting tool also has high edge line toughness and/or shows high comb crack resistance in milling operations of one or more of ISO-P, ISO-S and ISO-M workpiece materials.

The present invention relates to a coated cutting tool for metal machining comprising a rake face and a flank face and a cutting edge inbetween, the coated cutting tool further comprises a cemented carbide substrate body and a coating thereon, wherein the coating comprises a from 0.2 to 15 pm thick layer of a metal nitride, MeN, wherein Me is one or more metals of group 4 to 6 in the periodic table of elements or one or more metals of group 4 to 6 in the periodic table of elements in combination with Al and/or Si, the MeN is either a monolithic layer or a multilayer of two or more sublayers of different elemental composition, the cemented carbide comprises WC, in the form of WC grains within a binder phase,

- there is an uppermost part of the cemented carbide substrate body wherein there are WC grains comprising an uppermost WC interface to the coating and wherein there is a binder phase comprising an uppermost binder phase interface to the coating,

- the WC grains comprising an uppermost WC interface to the coating has an uppermost zone adjacent to the coating which, in addition to W and C, comprises N and one or more of Ti, Cr, Zr, Nb, Mo and V, the uppermost zone being from 1 .5 to 8 nm, preferably from 2 to 6 nm, more preferably from 2 to 4 nm, most preferably from 2 to 3.5 nm,

- said uppermost zone of the WC grains, adjacent to the coating, comprises <0.6 at% of any noble gas element or combination of noble gas elements.

As a noble gas element is herein meant an element belonging to the group of Ne, Ar, Kr and Xe.

The noble gas element content is herein determined by TEM-EDX.

The uppermost zone of the WC grains, adjacent to the coating, suitably comprises <0.5 at% of any noble gas element or combination of noble gas elements, preferably <0.4 at%, more preferably <0.3 at%, even more preferably <0.2 at%, most preferably <0.1 at%, or not any detectable amount.

In one embodiment, the uppermost zone of the WC grains, adjacent to the coating, suitably comprises >0.1 at% but <0.6 at% of any noble gas element or combination of noble gas elements, or >0.2 at% but <0.5 at%.

It has surprisingly been found that by providing an outermost zone of a WC grain at the surface of a cemented carbide substrate body having a metal nitride coating thereon, a long tool life is provided if the outermost zone of WC grains comprises one or more of Ti, Cr, Zr, Nb, Mo and V, as well as N, and that the outermost zone has a very low content of any noble gas element, such as usually Ar used in a PVD process. Noble gas elements, if substantially present, have been found to have an negative impact on tool life of a coated cutting tool having one or more metal nitride layers deposited on the cemented carbide substrate body.

The coated cutting tool herein disclosed shows at least excellent resistance to secondary notch wear, which is a type of local flank wear, in combination with excellent flaking resistance in finishing turning operation of ISO S and drilling operations of ISO-S and ISO-M workpiece materials. Also, high edge line toughness and comb crack resistance in milling operations of ISO P, ISO-S and ISO-M workpiece materials.

In one embodiment, the WC grains comprising an uppermost WC interface to the coating has an uppermost zone adjacent to the coating which, in addition to W and C, comprises N and one or more of Ti, Cr, Zr, and V.

In one embodiment, the WC grains comprising an uppermost WC interface to the coating has an uppermost zone adjacent to the coating which, in addition to W and C, comprises N and one or more of Ti and Cr.

In one embodiment, the WC grains comprising an uppermost WC interface to the coating has an uppermost zone adjacent to the coating which, in addition to W and C, comprises N and Ti.

The MeN layer has suitably a thickness of from 0.5 to 10 pm, preferably from 0.5 to 5 pm, most preferably from 1 to 3 pm.

The MeN layer is in one embodiment the innermost layer of the coating adjacent to the cemented carbide substrate body.

In the MeN layer, Me is suitably one or more of Ti, Cr and Zr, or one or more of Ti, Cr and Zr in combination with Al and/or Si.

The MeN layer is suitably any one of TiN, TiAIN, TiAISiN, TiAICrN, TiAICrSiN, TiAIZrN, TiAICrAIN, TiAISiN, CrAIN, or CrAISiN.

In one embodiment the MeN layer is a monolithic layer.

In one embodiment the MeN layer is Tii-_XAI_XN, 0.35<x<0.67, or 0.45<x<0.65, or 0.55<x<0.62.

In one embodiment the MeN layer is Tii-_PAI_PN, 0.68<p<0.95, or 0.70<p<0.90, or 0.75<p<0.85.

In one embodiment the MeN layer is a multilayer of alternating sub-layers (MeiN, Me2N, ...MenN, n is a number from 2 to 5, or from 2 to 4, or from 2 to 3, of different elemental composition. Mei, Me2, ...Men are each one or more of Me is one or more metals of group 4 to 6 in the periodic table of elements or one or more metals of group 4 to 6 in the periodic table of elements in combination with Al and/or Si. The average sublayer thicknesses of the alternating sub-layers (Me-iN, Me2N, ...MenN) are each from 1 to 100 nm, or from 2 to 50 nm, or from 3 to 20 nm.

In one embodiment, Me-i, Me2, ...Men are each one or more of Ti, Cr and Zr, or one or more of Ti, Cr and Zr in combination with Al and/or Si.

As embodiments of MeN being a multilayer can be mentioned a multilayer of TiAIN and TiSiN sub-layers, a multilayer of TiAIN, TiSiN and CrAIN sub-layers, a multilayer of TiAIN and TiAISiN sub-layers, or a multilayer of TiAIN and AICrN sub-layers.

In an embodiment of MeN being a multilayer of TiAIN and TiSiN sublayers, an example of the multilayer is a multilayer of alternating sub-layers of a first sub-layer being Tii-_yAl_yN, 0.35<y<0.70, and a second sub-layer being Tii- zSizN, 0.12<z<0.25. Another example is a multilayer of alternating sublayers of a first sub-layer being Tii-uAluN, 0.35<u<0.67, a second sub-layer being Tii-vSivN, 0.10<v<0.25, and a third sub-layer being Tii-_WAI_WN, 0.70<w<0.90.

In an embodiment of MeN being a multilayer of TiAIN, TiSiN and CrAIN sub-layers, an example of the multilayer is a multilayer of alternating sub-layers of a first sub-layer being Tii-_aAl_aN, 0.45<a<0.67, a second sub-layer being Cn- bAIbN, 0.60<b<0.80, and a third sub-layer being Tii-_cSi_cN, 0.14<c<0.25.

In an embodiment of MeN being a multilayer of TiAIN and TiAISiN sublayers, an example of the multilayer is a multilayer of alternating sub-layers of a first sub-layer being Tii-dAldN, 0.55<d<0.70, and a second sub-layer being Tii-_e- fAleSifN, 0.20<e<0.50, 0.13<f<0.25.

In an embodiment of MeN being a multilayer of TiAIN and AICrN sublayers, an example of the multilayer is a multilayer of alternating layers of a first sub-layer being Tii-_gAl_gN, wherein 0.63<g<0.95, and a second sub-layer being Cn-hAlhN, wherein 0.5<h< 0.9.

A very thin innermost metal nitride layer, different from MeN in composition, adjacent to the cemented carbide substrate body, will generally not have any negative effect of the performance of the coated cutting tool. Thus, in one embodiment there is a from 2 to 10 nm, or from 3 to 5 nm, thick innermost layer of the coating, being of different elemental composition than MeN, which is a nitride of one or more of Ti, Cr, Zr, Nb, Mo and V, or a nitride of one or more of Ti, Cr, Zr, Nb, Mo and V in combination with Al and/or Si, adjacent to the cemented carbide substrate body. As examples can be mentioned TiN, CrN, ZrN, NbN, MoN and VN. This innermost layer is directly followed by the MeN layer.

In another embodiment there is a from 2 to 500 nm, or from 3 to 200 nm, or from 3 to 100 nm, thick innermost layer of the coating, being of different elemental composition than MeN, which is a nitride of one or more of Ti, Cr, Zr, Nb, Mo and V, or a nitride of one or more of Ti, Cr, Zr, Nb, Mo and V in combination with Al and/or Si, adjacent to the cemented carbide substrate body. As examples can be mentioned TiN, CrN, ZrN, NbN, MoN and VN. This innermost layer is suitably directly followed by the MeN layer.

The crystal structure of WC in a cemented carbide substrate body is of hexagonal crystal structure. The MeN layer in the present invention is of cubic NaCI structure, or of a mixture of hexagonal crystal structure and cubic NaCI crystal structure.

The from 2 to 500 nm, or from 3 to 200 nm, or from 3 to 100 nm, thick innermost layer of the coating, being of different elemental composition than MeN, being a nitride of one or more of Ti, Cr, Zr, Nb, Mo and V, or being a nitride of one or more of Ti, Cr, Zr, Nb, Mo and V in combination with Al and/or Si, adjacent to the cemented carbide substrate body, is suitably of cubic NaCI structure.

In the present invention, the uppermost zone of the WC grains comprising an uppermost WC interface to the coating may be completely of a cubic NaCI crystal structure. Alternatively, the uppermost zone of the WC grains comprising an uppermost WC boundary facing the coating may comprise an inner part, i.e. , the part most distant from the coating, being of a hexagonal crystal structure and an upper part, i.e., the part closest to the coating, being of a cubic NaCI crystal structure.

Thus, in one embodiment, the crystal structure of the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is cubic NaCI structure. Furthermore, in one embodiment, at least the innermost quarter of the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is of hexagonal crystal structure and at least the uppermost quarter of the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is of cubic NaCI structure.

The crystal structures, cubic and hexagonal, are suitably being detected by TEM analysis.

In one embodiment, within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating there is a discontinuous transition, as seen in an STEM image, when going in the direction towards the coating, from lattice stripes of one direction being continuous with lattice stripes within the WC into lattice stripes of another direction being continuous with lattice stripes within the innermost part of the coating. The STEM image is prepared as herein described.

In one embodiment, within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating, the content of W decreases from a first content at the lower interface of the uppermost zone of the WC grains to a second content of W at the upper interface of the uppermost zone of the WC grains. The decrease in W content may be substantially continuous, or may be discontinuous, e.g., stepwise.

The first content of W within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is suitably from 40 to 70 at% , or from 45 to 65 at%.

The second content of W within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is suitably from 5 to 25 at% , or from 8 to 20 at%.

In one embodiment, within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating, the content of C decreases from a first content at the lower interface of the uppermost zone of the WC grains to a second content of C at the upper interface of the uppermost zone of the WC grains. The decrease in C content may be substantially continuous, or may be discontinuous, e.g., stepwise. The first content of C within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is suitably from 20 to 60 at%, or from 30 to 50 at%.

The second content of C within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is suitably from 0 to 25 at%, or from 2 to 20 at%.

In one embodiment, within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating, the content of N increases from a first content being at the lower interface of the uppermost zone of the WC grains to a second content of N at the upper interface of the uppermost zone of the WC grains. The increase in content of N may be substantially continuous, or may be discontinuous, e.g., stepwise.

The first content of N within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is suitably from 0 to 15 at%, or from 1 to 10 at%.

The second content of N within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is suitably from 30 to 55 at% , or from 35 to 50 at%.

In one embodiment, within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating, the content of one or more of Ti, Cr, Zr, Nb, Mo and V increases from a first content being at the lower interface of the uppermost zone of the WC grains to a second content of the one or more of Ti, Cr, Zr, Nb, Mo and V at the upper interface of the uppermost zone of the WC grains. The increase in content of the one or more of Ti, Cr, Zr, Nb, Mo and V may be substantially continuous, or may be discontinuous, e.g., stepwise.

The first content of the one or more of Ti, Cr, Zr, Nb, Mo and V within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is suitably from 0 to 10 at%, or from 0 to 5 at%.

The second content of the one or more of Ti, Cr, Zr, Nb, Mo and V within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is suitably from 15 to 40 at% , or from 20 to 35 at%. In one embodiment, the uppermost WC interface occupies 75 to 100% of a total interface between the cemented carbide substrate body and the coating, as measured in a cross sectional cut of the cutting tool perpendicular to the cemented carbide substrate body surface plane, suitably 80 to 98%, or 85 to 98%, or 90 to 96%, of a total interface between the cemented carbide substrate body and the coating, as measured in a cross sectional cut of the cutting tool perpendicular to the cemented carbide substrate body surface plane.

In one embodiment, the binder phase has an uppermost zone adjacent to the coating which, in addition to binder metal, comprises N, W and one or more of Ti, Cr, Zr, Nb, Mo and V, the uppermost zone having a thickness of from 1 to 5 nm, preferably from 1.5 to 3 nm.

In one embodiment, the uppermost zone of the binder phase, adjacent to the coating, further comprises C.

In one embodiment, the uppermost zone of the binder phase, adjacent to the coating, comprises < 1 .5 at% of a noble gas element or combination of noble gas elements, preferably < 1 at%.

In one embodiment, the uppermost zone of the binder phase, adjacent to the coating, suitably comprises >0.1 at% but <1 .5 at% of any noble gas element or combination of noble gas elements, or >0.2 at% but <1 at%.

The noble gas element content is herein determined by TEM-EDX.

In one embodiment, within the uppermost zone of the binder phase, adjacent to the coating, the content of binder metal decreases from a first content being at the lower interface of the uppermost zone of the binder phase to a second content at the upper interface adjacent to the coating. The decrease in content of binder metal may be substantially continuous, or may follow an discontinuous, e.g., stepwise, decrease to the second content.

The first content of binder metal within the uppermost zone of the binder phase, adjacent to the coating is suitably from 20 to 45 at%.

The second content of binder metal within the uppermost zone of the binder phase, adjacent to the coating is suitably from 0 to 10 at%. In one embodiment, within the uppermost zone of the binder phase, adjacent to the coating, the content of N increases from a first content being at the lower interface of the uppermost zone of the binder phase to a second content at the upper interface adjacent to the coating. The decrease in content of N may be substantially continuous, or may follow an discontinuous, e.g., stepwise, decrease to the second content.

The first content of N within the uppermost zone of the binder phase, adjacent to the coating is suitably from 10 to 30 at%.

The second content of N within the uppermost zone of the binder phase, adjacent to the coating is suitably from 25 to 50 at%.

In one embodiment, within the uppermost zone of the binder phase, adjacent to the coating, the content of W shows a maximum, i.e. , both the content of W at the lower interface of the uppermost zone of the binder phase and the content of W at the upper interface adjacent to the coating, are lower than the W content at the maximum.

The maximum content of W within the uppermost zone of the binder phase, adjacent to the coating is suitably from 5 to 15 at%.

In one embodiment, within the uppermost zone of the binder phase, adjacent to the coating, the content of the one or more of Ti, Cr, Zr, Nb, Mo and

V increases from a first content being at the lower interface of the uppermost zone of the binder phase to a second content at the upper interface adjacent to the coating. The increase in content of the one or more of Ti, Cr, Zr, Nb, Mo and

V may be substantially continuous, or may follow an discontinuous, e.g., stepwise, decrease to the second content.

The first content of the one or more of Ti, Cr, Zr, Nb, Mo and V within the uppermost zone of the binder phase, adjacent to the coating is suitably from 0 to 15 at% , or from 3 to 10 at%.

The second content of the one or more of Ti, Cr, Zr, Nb, Mo and V within the uppermost zone of the binder phase, adjacent to the coating is suitably from 10 to 30 at% , or from 15 to 25 at%.

In one embodiment, the uppermost binder phase interface to the coating occupies 0 to 25%, or from 2 to 20%, or from 2 to 15%, or from 4 to 10%, of a total interface between the cemented carbide substrate body and the coating, as measured in a cross sectional cut of the cutting tool perpendicular to the cemented carbide substrate body surface plane.

The substrate of the coated cutting tool is a cemented carbide comprising WC in a binder phase of a metal binder.

Suitably, the cemented carbide comprises from 70 to 95 wt% WC, or from 80 to 94 wt% WC, or from 85 to 93 wt% WC.

The metal binder can be any suitable binder metal used in cemented carbide substrates. The metal binder is suitably Co, Ni or Fe, or combinations thereof. In one embodiment the metal binder is Co.

The binder metal content in the cemented carbide is suitably from 5 to 18 wt%, or from 6 to 14 wt%. The cemented carbide may comprise additional constituents, besides WC and binder metal, commonly used in the art, such as cubic carbides or carbonitrides of one or more elements of group 4 and 5 in the periodic table of elements, such as carbides or carbonitrides of one or more of Ti, Ta and Nb, also called gamma phase, the amount being, for example, >0 wt% but <25 wt%, or from 0.1 to 10 wt%. Further components like Cr are possible in the cemented carbide substrate.

In one embodiment the cemented carbide comprises from 5 to 18 wt%, or from 6 to 14 wt%, binder metal, from 0 to 15 wt% cubic carbides or carbonitrides of one or more elements of group 4 and 5, up to 3 wt% Cr, up to 300 ppm by weight of one or metals being Ti, Ta, Nb, V and Zr, and balance WC.

The WC grain size is suitably 0.1 to 2 pm, or from 0.2 to 1.5 pm, or from 0.3 to 1 pm.

The grain size of the WC, d, is herein determined from the value of magnetic coercivity. The relationship between coercivity and grain size of WC is described, e.g., in Roebuck et al., Measurement Good Practice No. 20, National Physical Laboratory, ISSN 1368-6550, November 1999, Revised February 2009, Section 3.4.3, pages 19-20. For the purposes of this application the grain size of the WC, d, is determined according to formula (8) on page 20 in the above-mentioned literature:

K=(ci+diWco)+ (c₂+d₂Wco)/d. Re-arranging one gets: d = (C2+d2Wco)/ (K-(c-i+diWco)), wherein d= WC grain size of the cemented carbide body, K= coercivity of the cemented carbide body in kA/m, herein measured according to standard DIN IEC 60404- 7, Wco = wt% Co in the cemented carbide body, ci = 1 .44, C2 = 12.47, di = 0.04, and d2 = -0.37.

The coated cutting tool can be a cutting tool insert, a drill, or a solid endmill, for metal machining. In the case of the cutting tool being an insert it is suitably a milling, drilling or turning insert.

The layer, or layers, of the coating are deposited in a PVD process. Any type of PVD process may be used such as reactive sputtering, HIPIMS, ion plating or cathodic arc evaporation. Preferably, a cathodic arc evaporation process is used.

Thus, in one embodiment the layer of The MeN layer, as well as the in one embodiment 2 to 500 nm, or from 3 to 200 nm, or from 3 to 100 nm, thick innermost layer of the coating, being of different elemental composition than MeN, which is a nitride of one or more of Ti, Cr, Zr, Nb, Mo and V, or a nitride of one or more of Ti, Cr, Zr, Nb, Mo and V in combination with Al and/or Si, adjacent to the cemented carbide substrate body, are both cathodic arc deposited layers.

Methods:

Preparation of TEM lamellas for analysis:

Scanning electron and focused ion beam microscopy (SEM/FIB) (Helios NanoLab 650, FEI) was used for fabrication of site specific thin lamellas for transmission electron microscopy (TEM). No noble gas ion bombardment must be used during the preparation of the TEM sample since the noble gas content is one feature defining the present invention and use of a noble gas in a sample preparation might influence later measurements. A standard lift out technique was used with one or two low kV steps, 5kV and in some cases also 2kV. The TEM lamella thickness was aimed at to be thinner than 100 nm. The TEM lamellas were obtained by cutting a section including the uppermost part of the cemented carbide substrate body and the lowermost part of the coating in a direction perpendicular to the surface of the substrate body. The TEM lamellas were cut at a position on a flank face at a position of about 150 to 300 pm, preferably at about 200 pm, distance from the surface plane of a rake face. Also, there was a distance of at least 1 mm away from any other flank face. See a schematic visualisation of the position in Fig. 4. The TEM lamellas contained the full coating thickness of the samples and at least 2 pm of the uppermost part of the substrate.

TEM analysis:

TEM data, including scanning TEM (STEM) images, EDS and electron energy loss spectroscopy (EELS) images, were collected on either a Titan G2 or a Themis aberration-corrected (image and probe) TEM operated at 300 kV. EDX data were collected on a SuperX detector and EELS data on a Gatan Quantum ERS system. STEM images were collected at a camera length of 29.5 mm on Gatan ADF, Gatan HAADF (for Titan G2 only) and FEI HAADF detectors. The beam convergence angle was 21 .4 mrad for Titan G2 and 21.0 mrad for Themis. The beam current for image acquisition was ~100 pA and for spectrum imaging 350-600 pA.

STEM image and spectrum image analysis were done in GMS version 3.53 for Titan G2 and GMS version 3.60.4437.0. for Themis. EDX quantification was done in Broker Esprit version 1 .9.4 on data exacted from spectrum images.

EELS characterisation details:

EELS spectrum images were acquired on a Cs image and probe corrected Titan G2, or Themis, 60-300 High Base TEM operated in STEM mode with spot size 9 for Titan G2, and spot size 6 for Themis, at 300kV using a Gatan GIF Quantum ERS spectrometer with a nominal camera length of 29.5mm and a C2 50pm aperture corresponding to a 21.3mrad convergence semi-angle and using a current of approximately 0.35nA to 0.4nA. A Gatan Digital Micrograph 64-bit software version 2.32.888.0 for Titan G2 and 3.32.2403.0 for Themis, was used for the acquisition of dual-EELS spectrum images, i.e. low-loss and high-loss EELS data. Simultaneously image data was acquired using an FEI High Angle Annular dark field (HAADF) detector, a Gatan Annular darkfield (ADF) detector and a Gatan HAADF detector (for Titan G2 only) in addition to EDX-data acquired with a Super-X EDX detector using all three/four detectors. For the acquisition and quantification the convergence semi angle of 21 ,3mrad and a collection semi angle of 37.8mrad for Titan G2 and 35.0 mrad for Themis (5mm GIF entrance aperture) were used. Energy dispersion of 1eV per channel was used for Dual EELS acquisition. Areas with sharpest interfaces between substrate and coating were localised and characterised.

For EELS quantification a Gatan GMS 3 Digital Micrograph software was used, version 3.53.4031 .2 for Titan G2 and version 3.60.4437.0 for Themis. Spectrum Images and Gatan ADF STEM images were used for the calculation of EELS curves and extraction of intensity profiles, respectively. In the Global Info and Global Tags under Prefs in Quantification Pre-edge buffer was set to 7.0eV, SI Bkgd average nearest neighbours set to 2, disable model Electron energy-loss near edge structure (ELNES) set to FALSE, Do bkgd average set to TRUE, exclude ELNES set to TRUE, Include ELNES integral set to FALSE, Model ELNES set to TRUE, Splice model ELNES smoothly set to TRUE, post edge delay set to 50eV and Support model ELNES set to TRUE. ELNES width was set to 40eV and N ELNES iterations set to 10.

In Elemental Quantification window for maps, disable Model ELNES’ for 2D SI maps is unchecked.

It is important to correct for plural scattering using low-loss data including the zero-loss peak acquired at the same time as the core-loss data including the edges. For the quantification, care was taken to select the chemical shifts and ELNES and signal windows such that the modelled ELNES and cross-section curve followed the measured spectrum intensities as good as possible. This was checked for all elements and spectrum images for each sample and adjusted if needed, see below for an example of values used. Thickness of the TEM specimen in the analysed region was approximately between 0.7 and 1.3 t/lambda.

Examples of parameter settings used for quantifying different elements in an EELS spectrum image are disclosed below. The precise combination of settings to be used depend on the TEM equipment used for retrieving the EELS curves as well as the elemental composition of a specimen.

For C-K signal extraction, the edge energy was set to 283 eV, Background model to Power Law, Fit range 259.9 to 364.9eV, Signal sum width to 39.1 eV (excludes ELNES), ELNES width for Model ELNES to 42 eV with N iter 50 and Hydrogenic Cross section model with a chemical shift 0 eV, including plural scattering.

For N-K signal extraction, the edge energy was set to 401 eV, no Overlap C-K considered, Background model to Power Law, Fit range 350.9 to 583.9 eV, Signal sum width to 182.3 eV, ELNES width for Model ELNES to 46.0 eV with N iter 50 and Hydrogenic Cross section model with a chemical shift - 10.0 eV, including plural scattering.

For Ti-L signal extraction, the edge energy was set to 455 eV, Overlap N-K considered, Background model to Power Law, Fit range 350.9 to 583.9eV, Signal sum width to 128.5 eV, ELNES width for Model ELNES to 43.4 eV with N iter 50 and Hydrogenic (with white lines) Cross section model with a chemical shift -8.0 eV, including plural scattering.

For Zr-M signal extraction, the edge energy was set to 180 eV, no Overlap considered, Background model Power Law, Fit range 166.0 to 240.0 eV, Signal sum width to 20.0 eV (excludes ELNES), ELNES width for Model ELNES to 40.0 eV with N iter 50 and Hartree Slater Cross section model with a chemical shift +4.0 eV, including plural scattering.

For V-L signal extraction, the edge energy was set to 512 eV, Overlap Ti-L selected, Background model Power Law, Fit range 333.0 to 555.0 eV, Signal sum width to 22.1 eV (excludes ELNES), ELNES width for Model ELNES to 20.0 eV with N iter 50 and Hydrogenic (white lines) Cross section model with a chemical shift -7.0 eV, including plural scattering. For Co-L signal extraction, the edge energy was set to 778 eV, no Overlap V-L or Ti-L considered, Background model to Power Law, Fit range

624.9 to 1051.9 eV, Signal sum width to 233.3eV, ELNES width for Model ELNES to 40.0 eV with N iter 50 and Hydrogenic Cross section model with a chemical shift 0.0 eV, including plural scattering.

For Al-K signal extraction, the edge energy was set to 1559 eV, no Overlap Co-L considered, Background model to Power Law, Fit range 1253.9 to

1693.9 eV, Signal sum width to 94.3eV (excludes ELNES), ELNES width for Model ELNES to 40.0 eV with N iter 50 and Hydrogenic Cross section model with a chemical shift -6.0 eV, including plural scattering.

For W-M signal extraction, the edge energy was set to 1809 eV, no overlap Al-K considered, Background model to Power Law, Fit range 1652.9 to

2081 .9 eV, Signal sum width to 222.7 eV (excludes ELNES), ELNES width for Model ELNES to 50.0 eV with N iter 50 and Hartree-Slater Cross section model with a chemical shift -3.0 eV, including plural scattering.

These examples of parameter settings show the approximate range of variation for the values for chemical shifts and ELNES and signal windows such that the modelled ELNES and cross-section curve followed the measured spectrum intensities as good as possible.

Elemental quantification maps were calculated based on the above example settings. Elemental profiles were extracted perpendicular to the coating and substrate interface, using a subset of the mapped area with the most well defined interface. A width of 50 pixels for the extraction of the profile was used. To acquire the DualEELS spectrum images and STEM images step length of around 1 .5 A and 3 A were used.

Thickness of the uppermost zone of the WC grains comprising an uppermost WC interface to the coating:

The thickness of the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is herein defined as follows. An annular dark-field scanning transmission electron microscope (ADF-STEM) image is obtained when a zone axis of a WC grain is aligned parallel to the beam of the TEM and a bright zone is seen in an uppermost zone of the WC grain comprising an uppermost WC interface to the coating.

A diagram of the intensity profile corresponding to this bright zone is obtained with the x-axis having a scale showing distance in nm and y-axis a scale showing the intensity. Within the bright zone of the uppermost zone in the WC grains there is a maximum intensity in the intensity profile. A half maximum peak intensity value is calculated, as calculated from a baseline intensity level on the side at the beginning of the intensity profile along the x-axis and its corresponding position on the x-axis is regarded as the innermost boundary of the uppermost zone of a WC grain. Correspondingly, a half maximum peak intensity value is calculated, as calculated from a baseline intensity level on the side at the end of the intensity profile along the x-axis and its corresponding position on the x-axis is regarded as the outermost boundary of the uppermost zone of a WC grain. The difference between the two positions on the x-axis obtained is defined as the thickness of the uppermost zone of WC grains adjacent to the coating. See further Fig. 5a or 6a for visualisation.

Thickness of the uppermost zone of the binder phase adjacent to the coating:

The thickness of the uppermost zone of the binder phase adjacent to the coating is determined is defined as follows. An annular dark-field scanning transmission electron microscope (ADF-STEM) image is obtained when a zone axis of the binder metal is aligned parallel to the beam of the TEM and a bright zone is seen in an uppermost zone of the binder phase adjacent to the coating the WC grain comprising an uppermost WC interface to the coating.

A diagram of the intensity profile corresponding to this bright zone is obtained with the x-axis having a scale showing distance in nm and y-axis a scale showing the intensity. Within the bright zone of the uppermost zone in the binder phase there is a maximum intensity in the intensity profile. A half maximum peak intensity value is calculated, as calculated from a baseline intensity level on the side at the beginning of the intensity profile along the x- axis and its corresponding position on the x-axis is regarded as the innermost boundary of the uppermost zone of the binder phase adjacent to the coating. Correspondingly, a half maximum peak intensity value is calculated, as calculated from a baseline intensity level on the side at the end of the intensity profile along the x-axis and its corresponding position on the x-axis is regarded as the outermost boundary of the uppermost zone of the binder phase ajacent to the coating. The difference between the two positions on the x-axis obtained is defined as the thickness of the uppermost zone of the binder phase adjacent to the coating. See further Fig. 7 for visualisation.

Noble gas content determination:

The noble gas content, e.g., Ar, determination is made by analysing integrated EDX signals from a rectangular area on a spectrum image within the uppermost zone of a WC grain. The noble gas determination was made by in a STEM image selecting a rectangular area within the uppermost zone of a WC grain, or a binder phase. The height of the rectangular area was selected to be 1.5 to 3 nm and placed in the middle of the uppermost zone of a WC grain adjacent to the coating, or the uppermost zone in a binder phase adjacent to the coating. The length of the rectangular area was selected to be at least 10 nm, for example 20-30 nm. At least three different uppermost WC grains, or uppermost binder phase locations of the cemented carbide substrate should be used in the determination.

In the measurements herein made, the pixel time was 20 ms and the number of passes was between 30-60 for the longexposure maps with drift correction.

In the case there is a certain, but very low, amount of noble gas element, e.g., Ar, present within the uppermost zone of a WC grain, or a binder phase, so that a visible peak thereof is seen in a spectrum retrieved, the noble gas peak in a spectrum should typically disappear when comparing spectrum in WC and coating if the rectangular area defined above is moved into the pure WC or into the coating. Method for determining the occupancy of the uppermost WC interface and the uppermost binder phase interphase to the coating:

An insert was grinded and then polished in steps until a final step using a 1 pm diamond-oil slurry on a piece of paper put on a hard disc. This method gives very low interface rounding and substantially no preferential etching of binder metal, such as Co. The measurement at the substrate-coating interface was made on a cross section of an insert. The combination of grinding and polishing removes about 1 .4 mm of the insert full width.

The measurement was made at 10000X magnification giving a full image width of about 11 ,4 pm (high res. micrographs 3072 x 2304 pix to permit further zoom if needed). The regions with binder metal-contact with the upper coating were measured and summed together. The % coverage of WC (total image width) relative binder phase (summed length) was then calculated.

The measurements were made about 200 pm from the edge line on the flank side of the insert. An average value from measurements on images of at least three different positions gave the stated values. In the measurements a length of at least 10 pm per image should be used.

Description of drawings

Figure 1 shows a schematic view of one embodiment of a cutting tool (1 ) having a rake face 2 and flank faces 3 and a cutting edge 4. The cutting tool 1 is in this embodiment a milling insert.

Figure 2 shows a schematic view of one embodiment of a cutting tool 1 having a rake face 2 and flank face 3 and a cutting edge 4. The cutting tool 1 is in this embodiment a turning insert.

Figure 3 shows a schematic view of a cross section of an embodiment of the coated cutting tool of the present invention having a substrate 5 of cemented carbide and a coating 6.

Figure 4 shows a schematic view of a flank face 3 of a cutting tool 1 wherein the position for the TEM analysis is indicated. Figure 5a shows an intensity curve from an ADF-STEM image of sample

1 (invention). The curve starts within an uppermost WC grain and goes into the coating. The limits of the uppermost zone as herein defined are seen.

Figure 5b shows EELS curves of sample 1 (invention) when going from within an uppermost WC grain and into the coating.

Figure 6a shows an intensity curve from an ADF-STEM image of sample

2 (invention). The curve starts within an uppermost WC grain and goes into the coating. The limits of the uppermost zone as herein defined are seen.

Figure 6b shows EELS curves of sample 2 (invention) when going from within an uppermost WC grain and into the coating.

Figure 7 shows an intensity curve from an ADF-STEM image of sample 2 (invention). The curve starts at a distance within the uppermost binderphase below the interface to the coating and goes into the coating. The limits of the uppermost zone as herein defined are seen.

Examples

Example 1 :

Sintered cemented carbide cutting tool insert blanks of the geometries SNMA 120408 (flat insert for analysis), CNMG120804-MM and SM (turning insert) and R390-11T308M-PM (milling insert) were provided and placed in a PVD chamber.

The composition of the cemented carbide was 7 wt% Co, 0.7 wt% Cr, 0.01 wt% Ta and 0,014 at% Ti and rest WC for the CNMG120804-SM insert. The composition of the cemented carbide was 10 wt% Co, 0.4 wt% Cr and rest WC for the SNMA120804-MM insert and R390-11T308M-PM inserts.

The WC grain size, as herein defined, was 0.4 pm for the cemented carbide containing 7 wt% Co and 0.5 pm for the cemented carbide containing 10 wt% Co.

The cemented carbide blanks were coated by cathodic arc evaporation in a PVD vacuum chamber comprising six arc flanges, each flange comprising several cathode evaporators. Targets (sources) of Ti40AI60 were mounted in the evaporators in 3 or 4 flanges in a batch coater having 4 or 6 active flanges, respectively. Ti targets (sources) were mounted in 1 flange. The targets were circular and planar with a diameter of 100 mm available on the open market. Suitable arc sources to be used within this invention are the ones called Super Fine Cathode (SFC) from Kobelco (Kobe Steel Ltd.), which was herein used in the treatments and deposition of coatings, except in comparative sample 9. SFC cathodes are discussed in Yamamoto et al., "Cutting Performance of Low Stress Thick TiAIN PVD Coatings during Machining of Compacted Graphite Cast Iron (CGI)", Coatings 2018, 8, 38; doi:10.3390/coatings8010038.

The PVD chamber comprises a circular rotatable substrate table and the uncoated cutting tool insert blanks, which each has a hole like the inserts in the schematic figures 1 and 2, were mounted on pins located at the circumference of the substrate table. The table diameter was 0.82 m. The distance between the circumference of the substrate table and the targets was about 27 cm.

The mounting of the inserts was such that the flank faces of the inserts would substantially face the cathode evaporators during rotation in the PVD chamber during the sample preparation processes.

The cutting tool insert blanks underwent a three-fold rotation in the PVD chamber during deposition of the coating. The table rotation speed was 5 rpm.

The chamber was pumped down to high vacuum (less than 10’² Pa) and heated to about 350-450°C by heaters located inside the chamber.

The cemented carbide blanks were subjected to treatments as follows:

At first, all cemented carbide blanks were subjected to an Ar ion etching step. The purpose of the Ar etching is to remove any loose fragments of WC that may be present on the substrate surface and also to remove any binder phase present on the uppermost WC grains facing the surface after the ER- blasting. In this etching step the substrates are cleaned thourogly from such defects. In the following sample preparation a substrate bias level of -200V and about 0,7 Pa of Ar-pressure was used, resulting in an average bias current of about 15-17 A for the used substrate table. Five separate runs with different process conditions were made. Since there were two different substrates used the samples are denoted 1a, 1b, 2a, 2b, etc. Within a same sample, for example 1a, it is included all different insert geometries.

For samples "a" the composition of the cemented carbide was 7 wt% Co, 0.7 wt% Cr, 0.01 wt% Ta and 0,014 at% Ti and rest WC.

For samples "b" the composition of the cemented carbide was 10 wt% Co, 0.4 wt% Cr and rest WC.

In 8 separate runs a first step of Ar ion etching was performed. A DC bias voltage of -200V was used, at an Ar pressure of 0.7 Pa. The etch time were 55 min. Table 1 shows the samples.

Table 1 .

Then, in five of the separate runs (samples 1 , 2, 3, 5 and 6) a Ti ion treatment step was performed. In this step an arc current of 150 A was applied to the Ti target(s) in the PVD chamber, and in the different runs different bias voltage levels were applied to the cutting tool blanks as seen in Table 2. In comparative sample 3 a lower bias voltage level (-100 V) was used than used for the samples within the invention. Comparative sample 4 was, thus, not subjected to any Ti ion treatment step at all. Then, in comparative samples 5 and 6 a much higher bias voltage level (-1000 V and -600 V, respectively) was used than used for the samples within the invention. Further information of Ar gas pressure and treatment time are found in Table 2.

Table 2.

A layer of Ti0.40AI0.60N was deposited in the runs of all samples 1 -6.

The Ti0.40AI0.60N layer was deposited by cathodic arc evaporation in a gas containing N2 using the mounted targets of Ti40AI60. The substrate bias voltage when depositing the Ti0.40AI0.60N layer was -70 V DC (relative to the chamber walls), the total pressure (N2) was 4 Pa, and the arc current for each cathode was 150 A.

A Ti0.40AI0.60N layer having a thickness of about 2 pm was deposited on the inserts (measured on the flank 200 pm from the edge line). This formed the final Sample 1 (1 a, 1 b) (invention), Sample 2 (2a, 2b) (invention), Sample 3 (3a, 3b) (comparative), Sample 4 (4a, 4b) (comparative), Sample 5 (5a, 5b) (comparative), and Sample 6 (6a, 6b) (comparative).

For sample 1 there was a short time period of a few seconds where the Ti-target(s) were still on while the bias had been reduced to the level of the nitride step, causing net deposition of Ti, while the N2-gas was ramping up to the desired pressure. Then the Ti-target(s) were turned off and the Ti-AI targets were ignited. This sequence resulted in that a thin (3-6 nm) layer of TiN was deposited directly on top of the cemented carbide substrate before the deposition of the TiAIN layer started. Sample 2 was made with an altered cycle where its correponding transition sequence when going from Ti ion treatment to TiAIN deposition did not result in any innermost thin layer of TiN.

In one of the separate runs (sample 7) seen in Table 1 a Zr ion treatment step was performed. In this step an arc current of 170 A was applied to the Zr target(s) in the PVD chamber, and in the different runs different bias voltage levels were applied to the cutting tool blanks as seen in Table 3. Further information of Ar gas pressure, Ar flow and treatment time are found in Table 3.

Table 3.

A layer of Ti0.40AI0.60N was then deposited in the run of sample 7.

The Tio.4oAlo.6oN layer was deposited by cathodic arc evaporation in a gas containing N2 using the mounted targets of Ti40AI60. The substrate bias voltage when depositing the Ti0.40AI0.60N layer was -70 V DC (relative to the chamber walls), the total pressure (N2) was 4 Pa, and the arc current for each cathode was 150 A.

A Ti0.40AI0.60N layer having a thickness of about 2 pm was deposited on the inserts (measured on the flank 200 pm from the edge line). This formed the final Sample 7 (7a, 7b) (invention).

In one of the separate runs (sample 8) seen in Table 1 a V ion treatment step was performed. In this step an arc current of 170 A was applied to the V target(s) in the PVD chamber, and in the different runs different bias voltage levels were applied to the cutting tool blanks as seen in Table 4. Further information of Ar gas pressure, Ar flow and treatment time are found in Table 4. Table 4.

A layer of Ti0.40AI0.60N was deposited in the run of sample 8.

A Ti0.40AI0.60N layer having a thickness of about 2 pm was deposited on the inserts (measured on the flank 200 pm from the edge line). This formed the final Sample 8 (8a, 8b) (invention).

Finally, the process and set-up for making Sample 2 (invention) was repeated but instead of using a Super Fine Cathode (SFC) from Kobelco (Kobe Steel Ltd.) a so called Fine Cathode (FC) from Kobelco (Kobe Steel Ltd.) was used. The sample produced is called Sample 9.

The same geometries of sintered cemented carbide cutting tool insert blanks were used in the process, as well as the same cemented carbide substrates, as used for making Sample 2.

At first, all cemented carbide blanks were subjected to an Ar ion etching step. The purpose of the Ar etching is to remove any loose fragments of WC that may be present on the substrate surface and also to remove any binder phase present on the uppermost WC grains facing the surface after the ER- blasting. In this etching step the substrates are cleaned thourogly from such defects. In the following sample preparation a substrate bias level of -200V and about 0,7 Pa of Ar-pressure was used, resulting in an average bias current of about 15-17 A for the used substrate table. A first step of Ar ion etching was performed. The parameters used are seen in Table 5.

Table 5.

Then, a Ti ion treatment step was performed. The parameters used are seen in Table 6.

Table 6.

Then, a layer of Ti0.40AI0.60N was deposited. The Ti0.40AI0.60N layer was deposited in the same manner and at the same conditions as used for making Sample 2. A Ti0.40AI0.60N layer having a thickness of about 2 pm was deposited on the inserts (measured on the flank 200 pm from the edge line). This formed the final Sample 9 (9a, 9b) (comparative).

TEM analysis was performed on the samples. The procedure as described herein under section "Methods" was followed.

STEM images were obtained as described herein and the interface region between the cemented carbide substrate body and the coating was studied.

The thicknesses of the uppermost zone of the WC grains comprising an uppermost WC interface to the coating and the uppermost zone of the binder phase adjacent to the coating were determined for sample(s) within the invention. The procedures as described herein under section "Methods" were followed. See results in Table 7.

The Ar content in the defined uppermost zone (of WC grains and binder phase) of the samples was determined. The procedure as described herein under section "Methods" was followed. See results in Table 7.

The contents of elements within an investigated area going from the cemented carbide substrate into the coating were obtained by EELS. The procedure as described herein under section "Methods" herein was followed.

Fig. 5a shows an intensity curve from an ADF-STEM image of an uppermost WC grain and the lower part of the coating of sample 1 (invention). The limits of the uppermost zone are seen as herein defined.

Fig. 5b show EELS curves for sample 1 (invention) when going from within a WC grain into the coating.

Fig. 6a shows an intensity curve from an ADF-STEM image of an uppermost WC grain and the lower part of the coating of sample 2 (invention). The limits of the uppermost zone are seen as herein defined.

Fig. 6b shows EELS curves for sample 2 (invention) when going from within a WC grain into the coating.

Fig. 7 shows an intensity curve from an ADF-STEM image of an uppermost part of the binder phase and the lower part of the coating of sample 2 (invention). The limits of the uppermost zone are seen as herein defined. In table 7 presenting the results from some TEM measurements there is a notation under the sample number which metal was used in the metal ion treatment as well as the bias voltage used. Table 7.

For sample 3 (comparative), in which a metal ion treatment at -100V was made, there was no uppermost zone in WC and binder phase comprising W, C, N and Ti, and W, C, N and Ti, respectively. Instead, an about 40 nm thick metallic Ti layer was present as an innermost layer adjacent to the substrate surface.

For sample 4 (comparative), in which no metal ion treatment was made, there was a very thin (< 1 nm) uppermost zone in WC with gradients of W, C, N and Ti seen from EELS data but no bright zone in an ADF-STEM image was seen so it was not possible to measure any thickness according to the method herein defined.

For sample 5 (comparative), in which a metal ion treatment at -1000 V bias voltage was made, the Ar content in the uppermost zone in a WC grain adjacent to the coating as well as in the uppermost zone of the binder phase adjacent to the coating, was higher than the Ar content in these uppermost zones in the samples within the invention.

Also for sample 6 (comparative), in which a metal ion treatment at -600 V bias voltage was made, the Ar content in the uppermost zone in a WC grain adjacent to the coating as well as in the uppermost zone of the binder phase adjacent to the coating, was much higher than the Ar content in these uppermost zones in the samples within the invention.

For sample 9 there was no uppermost zone in WC and binder phase comprising W, C, N and Ti, and W, C, N and Ti, respectively. Instead, an about 50 nm thick metallic Ti layer was present as an innermost layer adjacent to the substrate surface.

It was concluded from EELS data of sample 1 (invention) and sample 2 (invention) that the uppermost zone of the WC grains comprising an uppermost WC interface to the coating comprised the elements W, C, Ti and N.

The content of W decreases from a first content at the lower interface of the uppermost zone of a WC grain to a second content of W at the upper interface of the uppermost zone of a WC grain. The first content of W within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is about 57 at%/ 55 at% (sample 1/sample 2). The second content of W within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is about 11 at%/ 12 at% (sample 1/sample 2).

The content of C decreases from a first content at the lower interface of the uppermost zone of the WC grains to a second content of C at the upper interface of the uppermost zone of the WC grains. The first content of C within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is about 37 at%/ 41 at% (sample 1/sample 2). The second content of C within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is about 6 at%/ 10 at% (sample 1/sample 2).

The content of N increases from a first content being at the lower interface of the uppermost zone of the WC grains to a second content of N at the upper interface of the uppermost zone of the WC grains. The first content of N within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is about 2 at%/ 1 at% (sample 1/sample 2). The second content of N within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is about 47 at%/ 42 at% (sample 1/sample 2).

The content of Ti increases from a first content being at the lower interface of the uppermost zone of the WC grains to a second content of Ti at the upper interface of the uppermost zone of the WC grains. The first content of Ti within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is about 0 at%/ 0 at% (sample 1/sample 2). The second content of Ti within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is about 30 at%/ 24 at% (sample 1/sample 2).

It was, furthermore, concluded from EELS data of sample 2 (invention) that the uppermost zone of the binder phase adjacent to the coating comprised the elements Co, W, Ti and N.

It was, furthermore, concluded from EELS data of sample 2 (invention) that the content of Co decreases from a first content being at the lower interface of the uppermost zone of the binder phase to a second content at the upper interface adjacent to the coating. The first content of Co within the uppermost zone of the binder phase, adjacent to the coating is about 33 at%. The second content of Co within the uppermost zone of the binder phase, adjacent to the coating is about 5 at%.

It was, furthermore, concluded from EELS data of sample 2 (invention) that the content of N increases from a first content being at the lower interface of the uppermost zone of the binder phase to a second content at the upper interface adjacent to the coating. The first content of N within the uppermost zone of the binder phase, adjacent to the coating is about 20 at%. The second content of N within the uppermost zone of the binder phase, adjacent to the coating is about 40 at%.

It was, furthermore, concluded from EELS data of sample 2 (invention) that the content of W shows a maximum, i.e. , both the content of W at the lower interface of the uppermost zone of the binder phase and the content of W at the upper interface adjacent to the coating, are lower than the W content at the maximum.

The maximum content of W within the uppermost zone of the binder phase, adjacent to the coating is about 10 at%.

It was, furthermore, concluded from EELS data of sample 2 (invention) that the content of Ti increases from a first content being at the lower interface of the uppermost zone of the binder phase to a second content at the upper interface adjacent to the coating. The first content of Ti within the uppermost zone of the binder phase, adjacent to the coating is about 8 at%. The second content of Ti within the uppermost zone of the binder phase, adjacent to the coating is about 20 at%.

It was concluded from EELS data of sample 7 (invention) and sample 8 (invention) that the uppermost zone of the WC grains comprising an uppermost WC interface to the coating comprised the elements W, C, Zr and N, and W, C, V and N, respectively.

The content of W decreases from a first content at the lower interface of the uppermost zone of a WC grain to a second content of W at the upper interface of the uppermost zone of a WC grain. The first content of W within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is about 53 at%/ 44 at% (sample 7/sample 8). The second content of W within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is about 16 at%/ 16 at% (sample 7/sample 8).

The content of C decreases from a first content at the lower interface of the uppermost zone of the WC grains to a second content of C at the upper interface of the uppermost zone of the WC grains. The first content of C within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is about 38 at%/ 38 at% (sample 7/sample 8). The second content of C within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is about 16 at%/ 12 at% (sample 7/sample 8).

The content of N increases from a first content being at the lower interface of the uppermost zone of the WC grains to a second content of N at the upper interface of the uppermost zone of the WC grains. The first content of N within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is about 1 at%/ 8 at% (sample 7/sample 8). The second content of N within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating is about 46 at%/ 41 at% (sample 7/sample 8).

It was, furthermore, concluded from EELS data of sample 7 (invention) that the uppermost zone of the binder phase adjacent to the coating comprised the elements Co, W, Zr and N. It was, furthermore, concluded from EELS data of sample 8 (invention) that the uppermost zone of the binder phase adjacent to the coating comprised the elements Co, W, V and N.

It was, furthermore, concluded from EELS data of sample 7 (invention) that the content of Co decreases from a first content being at the lower interface of the uppermost zone of the binder phase to a second content at the upper interface adjacent to the coating.

It was, furthermore, concluded from EELS data of sample 7 (invention) that the content of N increases from a first content being at the lower interface of the uppermost zone of the binder phase to a second content at the upper interface adjacent to the coating.

It was, furthermore, concluded from EELS data of sample 8 (invention) that the content of Co decreases from a first content being at the lower interface of the uppermost zone of the binder phase to a second content at the upper interface adjacent to the coating.

It was, furthermore, concluded from EELS data of sample 8 (invention) that the content of N increases from a first content being at the lower interface of the uppermost zone of the binder phase to a second content at the upper interface adjacent to the coating.

The EELS data further confirmed that sample 1 (invention) had an innermost, about 4 nm thick, layer of TiN before the TiAIN layer.

The occupancy of the uppermost WC interface of a total interface between the cemented carbide substrate body and the coating, as well as the occupancy of the uppermost binder phase interface to the coating was determined. The procedure as described herein under section "Methods" was followed. Table 8 shows the results.

Table 8.

Example 3:

Cutting tests were made in order to determine the performance of the samples made.

Explanations to terms used:

The following expressions/terms are commonly used in metal cutting, but nevertheless explained in the table below:

Vc (m/min): cutting speed in meters per minute fz (mm/tooth): feed rate in millimeter per tooth (in milling) fn (mm/rev) feed rate per revolution (in turning) z: (number) number of teeth in the cutter a_e (mm): radial depth of cut in millimeter a_P (mm): axial depth of cut in millimeter

Last stage machining (LSM):

Longitudinal turning

Work piece material: Inconel 718 aged, Hardness 428HB, D=180, L=600 mm, Holder: C5-DCLNL-35060-12, KAPR1 =95° Vc=30 m/min (60 m/min) fn=0.11 mm/rev a_P=0.2 mm with external cutting fluid

The tool life criteria is a max flank wear (notch), VB of 0.2 mm on secondary cutting edge. Flaking resistance:

The evaluation was made through turning test in austenitic steel. In order to provoke adhesive wear and flaking of the coating the depth of cut a_P was varied between 4 to 0 and 0 to 4 mm (in one run during radial facing). The inserts were evaluated through SEM analysis where flaked area was quantified through image treatment regarding of degree of white areas (being exposed WC after coating flaking).

Operation: Facing (turning)

Work piece material: Bar of austenitic stainless steel Sanmac 316L, L=200 mm, D=100 mm, -215 HB

Holder: C5-DCLNL-35060-12, KAPR1 =95°

Insert type: CNMG 120408-MM

Depth of cut a_P = 4 to 0, 0 to 4 mm

Cutting speed V_c = 100 m/min or 140 m/min

Feed rate f_z = 0.36 mm/rev

Cooling: yes, external

Edge line toughness (ELT):

Operation: 12 mm deep entrances in the material. The cutter body moves laterally 12 mm between each entrance.

Work piece material: Dievar unhardened, P3. 0.Z.AN, 617*207*100 mm Tool holder: R390-032C5-11 M, Dc=32 mm, overhang: 95 mm Insert: R390-11T308M-PM z=1

V_c=215 m/min fz=0.15 mm a_e=12 mm a_P— 3.0 length of cut=12mm without cutting fluid The cut-off criteria are chipping of at least 0.5 mm of the edge line Tool life is presented as the number of cut entrances in order to achieve these criteria.

Comb crack resistance (TTT):

Operation: Shoulder milling

Tool holder: R390-025B25-11 L, Dc=25 mm, overhang 150 mm

Work piece material: Toolox 33 (tool steel, P2.5.Z.HT ), L=600 mm, l=200 mm, h=100 mm,

Insert type: R390-11T308M-PM

Cutting speed V_c=275 m/min

Feed rate f_z=0.2 mm/rev z=1

Upmilling, zero-degree exit

Depth of cut a_P=3 mm

Radial engagement a_e= 12.5 mm with external cutting fluid

The criteria for end of tool life is a max. chipped height VB>0.3 mm.

Each pass is 200 mm

In the tables presenting the results from the different tests there is a notation under the sample number which metal was used in the metal ion treatment as well as the bias voltage used.

Last stage machining (LSM):

The tables 9 to 13 show five different test runs done at different times and with different bar diameters and/or work piece batches which to some extent affects the tool life in minutes. Comparative sample 4 which has the same coating as the other samples but is made without using any metal ion treatment step can be considered as a reference sample which makes different test runs easier to compare with each other. Table 9.

Table 10.

Table 11 .

Table 12.

Table 13.

It is concluded that the samples within the invention performed very well in the LSM tests above. Ti ion treatment at -200V gave the best result, but also Zr ion treatment at -200 V and V ion treatment at -200 V gave good results well above the results for the comparative samples where no metal ion treatment at all had been used, or where the metal ion treatment had been made at a too high bias voltage or at a too low bias voltage.

Thus, it is concluded that the bias voltage used during the metal ion treatment step is important. The samples within the invention were treated using -200 V. The comparative samples 3, 5 and 6 used -100 V, -600 V and -1000 V, respectively, and all gave very bad results in the LSM cutting test.

The choice of cathode type is also important. When identical conditions (i.e. , -200 V bias voltage) were used in a Ti treatment step but instead of using a Super Fine Cathode (SFC) from Kobelco (Kobe Steel Ltd.) a so called Fine Cathode (FC) from Kobelco (Kobe Steel Ltd.) was used (Sample 9), there was a net deposition of a 50 nm metallic Ti layer and very bad result in the LSM cutting test.

Turning operations of ISO-M workpiece materials, flaking resistance:

Tables 14 to 16 show three different testruns done at different times and with different work piece batches which to some extent affects the absolute flaked area.

Table 14.

Table 15.

Milling operation, edge line toughness (ELT) and comb crack resistance (TTT): Tables 16 to 18 show three different testruns done at different times and with different work piece batches which to some extent affects the absolute tool life.

Table 16.

Table 17.

Table 18.

Table 19 shows results from two different test runs done at different times which to some extent affects absolut tool life.

Table 19.

Claims

1. A coated cutting tool (1 ) for metal machining comprising a rake face (2) and a flank face (3) and a cutting edge (4) inbetween, the coated cutting tool (1 ) further comprises a cemented carbide substrate body (5) and a coating (6) thereon, wherein the coating (6) comprises a from 0.2 to 15 pm thick layer of a metal nitride, MeN, wherein Me is one or more metals of group 4 to 6 in the periodic table of elements or one or more metals of group 4 to 6 in the periodic table of elements in combination with Al and/or Si, the MeN is either a monolithic layer or a multilayer of two or more sublayers of different elemental composition, the cemented carbide comprises WC, in the form of WC grains within a binder phase,

- there is an uppermost part of the cemented carbide substrate body (5) wherein there are WC grains comprising an uppermost WC interface to the coating (6) and wherein there is a binder phase comprising an uppermost binder phase interface to the coating (6),

- the WC grains comprising an uppermost WC interface to the coating (6) has an uppermost zone adjacent to the coating (6) which, in addition to W and C, comprises N and one or more of Ti, Cr, Zr, Nb, Mo and V, the uppermost zone being from 1.5 to 8 nm, preferably from 2 to 6 nm, most preferably from 2 to 4 nm,

- said uppermost zone of the WC grains, adjacent to the coating (6), comprises <0.6 at% of any noble gas element or combination of noble gas elements, suitably <0.5 at%, preferably <0.4 at%, more preferably <0.3 at%.

2. A coated cutting tool (1 ) according to claim 1 , wherein, in the MeN layer, Me is one or more of Ti, Cr and Zr, or one or more of Ti, Cr and Zr in combination with Al and/or Si.

3. A coated cutting tool (1 ) according to any one of claims 1 -2, wherein, the MeN layer is the innermost layer of the coating (6) adjacent to the cemented carbide substrate body (5), MeN being a multilayer of alternating sub-layers (Me-iN, Me2N, ...MenN, n is a number from 2 to 5, or from 2 to 4, or from 2 to 3, of different elemental composition. Me-i, Me2, ...Men are each one or more of Me is one or more metals of group 4 to 6 in the periodic table of elements or one or more metals of group 4 to 6 in the periodic table of elements in combination with Al and/or Si.

4. A coated cutting tool (1 ) according to any one of claims 1-3, wherein,

- within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating (6), the content of W decreases from a first content at the lower interface of the uppermost zone of the WC grains to a second content of W at the upper interface of the uppermost zone of the WC grains, and,

- within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating (6), the content of C decreases from a first content at the lower interface of the uppermost zone of the WC grains to a second content of C at the upper interface of the uppermost zone of the WC grains, and,

- within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating (6), the content of N increases from a first content being at the lower interface of the uppermost zone of the WC grains to a second content of N at the upper interface of the uppermost zone of the WC grains, and,

- within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating (6), the content of one or more of Ti, Cr, Zr, Nb, Mo and V increases from a first content being at the lower interface of the uppermost zone of the WC grains to a second content of the one or more of Ti, Cr, Zr, Nb, Mo and V at the upper interface of the uppermost zone of the WC grains.

5. A coated cutting tool (1 ) according to claim 4, wherein, the first content of W within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating (6) is from 40 to 70 at%, and the second content of W within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating (6) is from 5 to 25 at%.

6. A coated cutting tool (1 ) according to any one of claims 4-5, wherein, the first content of C within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating (6) is from 20 to 60 at%. and the second content of C within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating (6) is from 0 to 25 at%.

7. A coated cutting tool (1 ) according to any one of claims 4-6, wherein, the first content of N within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating (6) is from 0 to 15 at%, and the second content of N within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating (6) is from 30 to 55 at%.

8. A coated cutting tool (1 ) according to any one of claims 4-7, wherein the first content of the one or more of Ti, Cr, Zr, Nb, Mo and V within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating (6) is from 0 to 10 at% , and the second content of the one or more of Ti, Cr, Zr, Nb, Mo and V within the uppermost zone of the WC grains comprising an uppermost WC interface to the coating (6) is from 15 to 40 at%.

9. A coated cutting tool (1 ) according to any one of claims 1 -8, wherein the uppermost WC interface to the coating (6) occupies 75 to 100%, or 80 to 98%, of a total interface between the cemented carbide substrate body (5) and the coating (6), as measured in a cross sectional cut of the cutting tool (1 ) perpendicular to the cemented carbide substrate body (5) surface plane.

10. A coated cutting tool (1 ) according to any one of claims 1-9, wherein, the uppermost binder phase interface to the coating (6) occupies 0 to 20%, or from 2 to 15%, of a total interface between the cemented carbide substrate body (5) and the coating (6), as measured in a cross sectional cut of the cutting tool perpendicular to the cemented carbide substrate body (5) surface plane.

11. A coated cutting tool (1 ) according to any one of claims 1 -10, wherein the binder phase has an uppermost zone adjacent to the coating (6) which, in addition to binder metal, comprises N, W and one or more of Ti, Cr, Zr, Nb, Mo and V, the uppermost zone being having a thickness of from 1 to 5 nm.

12. A coated cutting tool (1 ) according to claim 11 , wherein the uppermost zone of the binder phase, adjacent to the coating (6), comprises <1 .5 at% of a noble gas element or combination of noble gas elements.

13. A coated cutting tool (1 ) according to any one of claims 1 -12, wherein the cemented carbide comprises from 70 to 95 wt% WC.

14. A coated cutting tool (1 ) according to any one of claims 1 -13, wherein the binder metal is Co, the binder metal content in the cemented carbide is from 5 to 18 wt%.

15. A coated cutting tool (1 ) according to any one of claims 1 -14, wherein the coated cutting tool is a cutting tool insert, a drill, or a solid end-mill, for metal machining.