SE527906C2 - Coated cemented carbide cutter especially intended for turning stainless steel - Google Patents

Abstract

The present invention relates to a cutting insert particularly for turning of stainless steel comprising a cemented carbide substrate and a post-treated coating with a substrate of cemented carbide having a composition of 5.0-<8.0 wt% Co, 3.0-8.0 wt% cubic carbides of the metals Ti, Ta and Nb with a Ti/(Ti+Ta+Nb) ratio of 0.05-0.3 and balance tungsten carbide (WC) having a grain size of 1.5-3.5 mu in the as-sintered state. Further, the substrate has a surface zone of 5-30 mu with an enrichment of binder phase and a depletion of cubic carbides, and a coating having a first, innermost layer system of one or several layers of TiC x N y O z with x+y+z<=1 with a total thickness of 0.7-5.5 mu and a second multilayer system consisting of a totally 5-31 alternating layers of Al 2 O 3 and TiC x N y O z (x+y+z<=1), preferably -Al 2 O 3 and TiN, the Al 2 O 3 -layers having an individual layer thickness of <0.5 mu and the TiC x N y O z -layers <0.2 mu with a total thickness of the multilayer of 1.0-5.0 mu. The multilayer is exposed along the edge line and into the rake and flank face. In an alternative embodiment the multilayer is replaced by an Al 2 O 3 -layer.

Description

30 35 40 Un ha * J vb C: a \ verktyget. Damage of this kind, normally referred to as chip hammering and chip clamping, can be partially or completely avoided by choosing the right microgeometry on the active edge surfaces of the insert, but in many cases this possibility is not sufficient.

US. No. No. 5,786,069 discloses a coated turning insert suitable for turning in forged stainless steel components. The insert has a cemented carbide substrate containing 2-10% by weight of cubic carbides of elements belonging to groups IVb, Vb and / or VIb of the periodic table (y-phase), 5 -11% by weight of cobalt binder phase and the remainder tungsten carbide (WC ). The substrate has a binder phase with a high tungsten content and the sintered microstructure has a 15-35 μm deep Co-enriched surface zone free from y-phase. The coating consists of an inner layer of Ti (C, N, O) with columnar grains and an outer layer of fine-grained K-Al2O3. However, with respect to the cemented carbide substrate, the resistance to plastic deformation does not benefit from the combination of a nominally high binder phase content and a thick 7-phase depleted surface zone followed by a zone characterized by a high concentration peak of 7-phase. This will result in rapid wear and short life when machining austenitic and duplex stainless steels at high cutting speeds.

Multilayer coatings comprising two types of layers of different materials which are alternately laminated on the substrate, where each layer of the first layer has a certain thickness and each layer of the second layer has a different thickness, are known. The two layers should preferably have different crystal structure and / or at least different lattice parameters. An example is when Al2O3 growth is periodically interrupted by a short TiN coating process resulting in a (Al2O3 + TiN) n multilayer structure, see for example Proceedings of the 12th European CVD Conference page 8-349.

GB 2048960A discloses a multilayer coating having a plurality of alternating layers having a thickness of 0.02 to 0.1 μm consisting of hard materials of different compositions. In US 4,984,940, Bryant et al. a insert composed of a cemented carbide substrate with 6.1-6.5% by weight of cobalt, a coating comprising a base layer of titanium carbonitride followed by a multilayer coating. Said coatings consist of a number of alumina layers separated from and bonded to each other by a Group IVb metal nitride, such as titanium nitride.

A cemented carbide substrate with a coating comprising 6-8 alumina layers is also described in US 5,700,569. EP-A-1103635 W IS 20 25 30 35 (S1 hà “~ l \ 1> CI) Cïx 3 _; _ 4_ describes a cutting tool consisting of a cemented carbide sub 9.0-10.9 wt.% Cobalt and a coating comprising a "Moderate Temperature" CVD (MTCVD) precipitated TiCN layer and a multilayer composed of a total of 7-41 layers of K-Al2O3 and TiN or Ti (C, N) - Increased surface roughness of coatings by mechanical finishing to e.g. the friction between tool and workpiece is shown in EP-A-127416, EP-A-298729, EP-A-693574 and EP-A-683244.

Swedish Application No. 0300175-7 describes a coated cemented carbide insert with high demands on the wear resistance and toughness behavior of the cutting edge and is particularly suitable for general turning of stainless steel. The substrate has a 7-phase depleted and binder phase-enriched surface zone down to a depth of 5 to 50 μm. The composition of the substrate is 7.0 to 10.5% by weight of Co, 4.0 to 9.0% by weight of cubic carbides of elements from group IVb, Vb or VIb of the periodic table, preferably Nb, Ta and / or Ti, a nitrogen content of 0.01 to 0.2% by weight and the remainder tungsten carbide, WC. The coating contains an innermost layer system of up to three layers of TiCxNyO 2 (x + y + z 51), a second multilayer system comprising 5 to 31 alternating layers of Al 2 O 3 and TiCxNyO 2 (x + y + z§l), preferably 11 to 15 alternating layers of K-Al2O3 and TiN, and an outermost layer system comprising one or more layers of TiCxNy (x + y§1) or three layers in order of TiN-TiC-TiN or combinations thereof. Furthermore, the outermost surfaces of the coated insert are mechanically finished so that the multilayer and partly the innermost layer system are exposed along the edge line.

In view of the prior art, there is a need for a cutting tool for machining steel at high speeds in general and stainless steels in particular. This refers in particular to a insert that exhibits increased resistance to abrasive and adhesive wear, plastic deformation, chip hammering and chip pinch damage.

It is an object of the present invention to provide a insert capable of simultaneously resisting all the above-mentioned wear modes.

It is a further object of the present invention to avoid or mitigate problems associated with prior art tool products and to provide high performance tools for high cutting speeds. It is a further object of the present invention to provide a tool with excellent cutting performance in demanding stainless steel turning operations.

It has surprisingly been found that a cemented carbide insert with a substrate containing comparatively low levels of cobalt and cubic carbides, a thin 7-phase depleted and binder phase-enriched surface zone, in combination with a coating comprising a mechanically finished multilayer consisting of an amount of alternating Al TiCxNyOZ layers meet these requirements. The insert exhibits excellent resistance to plastic deformation, high edge toughness and also a sufficient resistance to adhesive wear, especially when turning austenitic and duplex stainless steels at high cutting speeds.

Fig. 1 is a scanning electron image (SEM) of a cross section of the surface of the substrate and coating of the present invention wherein: multilayer (Al 2 O 3 + TiN) 6 Al 2 O 3 and TiCxNy layer.

Fig. 2.1 is a schematic cross-section of the edge without finishing.

Z. γ-phase depleted and binder phase-enriched surface zone within the substrate A. TiN layer, B. columnar Ti (C, N) layer, C. TiN layer, D.

E.

Fig. 2.2 is a schematic cross-section of the edge with finishing according to the invention where the outermost layer E has been removed.

Fig. 2.3 is a schematic cross-section of the edge with a finishing according to the invention where the outermost layer E and the multilayer (Al2O3 + TiN) xAl2O3 have been removed.

Fig. 3 shows a schematic cross-section of the edge with a finishing according to the prior art.

More particularly, the invention relates to a WC + Co-based cemented carbide substrate with cubic carbide additives having a y-phase depleted and binder phase-enriched surface zone, a specific range for the WC grain size, a specific composition range for WC + Co, a specific Ti / ( Ti + Ta + Nb) ratio and a coating on the cemented carbide substrate comprising an innermost layer system consisting of a thin layer of equiaxial TiCxNyOz followed by a layer of columnar TiCxNyOz and a thin layer of equiaxial TiCxNyOz. This innermost layer system must contain at least two layers of TiCxNyOz with (x + y + zí1). On this layer system is a multilayer with a periodic variation of TiCxNyOz and Al2O3 layer (x + y + Z§l) 0Ch an outermost layer of Ticxuy (x + y5l) deposited.At least the outermost non-oxide layer is missing in the surfaces which are in direct contact with material from the workpiece around the cutting edge.

The composition of the cemented carbide substrate should comprise 5.0- <8.0 wt% Co, preferably 5.0- <7.0 wt% Co, and 3.0-8.0 wt% cubic carbides, preferably 4.0-7, 0% by weight of cubic carbides of the metals Ti, Ta and Nb and possibly other carbides of the elements from group IVb, Vb or VIb of the Periodic Table and the remainder tungsten carbide (WC). The average grain size for WC is 1.5-3.5 μm, preferably 2.0-3.0 μm. The addition of elements forming cubic carbides should be such that the Ti / (Ti + Ta + Nb) ratio is 0.05-0.3, preferably 0.1-0.25. The depth of zone Z should be 5-30 μm, preferably 5-25 μm. Said cubic carbides may contain some amount of N and O and the amount of N must be 0.01-0.2% by weight.

The hard and durable refractory coating (Fig. 1) deposited on the cemented carbide substrate according to the present invention comprises: - a first, innermost layer (A) of TiCxNyOz with x + y + zí1, preferably y> x and z <0 , 2, preferably y> 0.8 and z = 0, with uniaxial grains with size <0.5 μm and a total thickness <1.5 μm but> 0.1 μm preferably 0.1-0.6 μm . a second layer (B) of TiCXNyO 2 with x + y + z§l, preferably with z = 0, x> 0.3 and y> 0.3, more preferably x> 0.5, with a thickness of 0.4 -4.9 μm, preferably 1.5-4.0 μm with columnar grains. - a third layer (C) of TiCxNyOz with x + y + z§1, preferably y> x and z <0.2, more preferably y> 0.8 and z = 0, with equiaxed grains with size <0.5 μm and a total thickness <1.5 μm but> 0.1 μm, preferably 0.2-0.8 μm. the total thickness of the layers A + B + C is 0.7-5.5 μm, preferably 1.2-5.0 μm. Preferably, each of the layers A and C should be thinner than the layer B. - a multilayer (D) consisting of a plurality of alternating Al2O3 and TiCxNyOz layers (x + y + zíl), preferably K-Al2O3 and TiN layers. The innermost and outermost layers in the multilayer sequence are Al2O3 layers. The total number of layers, comprising both TiCxNyO 2 and Al 2 O 3 layers, is between 5 and 31, preferably 11 and 15 layers. The Al 2 O 3 layers have an individual layer thickness of 11 BJ \ J

The total thickness of the multilayer is 1.0-5.0 μm, preferably 1.5-4.0 μm. The grain size of each Al 2 O 3 layer is equal to or less than the thickness of the layer. an outermost layer system (E) consisting of one or more layers 1 of Ticxny coating (x + y51), preferably three to five layers in order of TiN, TiC, and TiN. The total thickness is <2.0 μm but> 0.1 μm, preferably 0.5-1.5 μm. the total thickness of the layers A + B + C + D + E is 2.0-9.0 μm, preferably 4.0-8.0 μm.

The outermost part of the coating is missing around the edge in the surface corresponding to the chip contact on the chip side and the contact with the workpiece on the release side. Preferably, the considered surface corresponds to the primary phase on the chip side when a primary phase exists on the current insert geometry so that coating is missing a distance from a point defined in Fig. 2.2 with a section perpendicular to the insert side plane on the chip side "a" and on the release side "b" . These distances depend on different cutting geometries and cutting sizes, etc., on the chip side preferably corresponding to 0.03 mm regardless of the existence of a primary phase or not, a> b, preferably a> 1.5b. In one embodiment only layer E is missing. In another embodiment both layers D and E are missing in parts of the surface.

Coated inserts of the present invention preferably comprising a cemented carbide substrate are made in such a way that a zone near the surface depleted of cubic carbide and enriched in binder phase is achieved after the addition of a low amount of nitrogen and sintering in vacuo before coating. The composition of the cemented carbide substrate comprises 5.0- <8.0 wt% Co, 3.0-8.0 wt% cubic carbides and the remainder is tungsten carbide (WC). The average grain size for WC is in the range 1.5-3.5 μm. The addition of elements forming cubic carbides should be such that the Ti / (Ti + Ta + Nb) ratio is 0.05-0.3, preferably 0.1-0.25. The depth of zone Z should be 5-30 pm, preferably 5-25 pm. Said cubic carbides may contain some amount of N and O and the amount of N must be 0.01-0.2% by weight. These microstructural constituents can be termed, for example, carbonitride or oxycarbonitride. The cemented carbide body is mainly prepared by mixing powder, grinding, spray drying, some pressing method followed by sintering according to conventional methods and pretreatment such as edge gradation and pre-coating cleaning. .

The body is then coated with - a first (innermost) layer (A) of TiCxNyOz with x + y + z§l, preferably y> x and z <0.2, preferably y> 0.8 and z = 0, with equilateral grains of size <0.5 μm and a total thickness of 0.1 μm using known chemical evaporation methods, CVD. a layer of TiCxNyOZ (B) with x + y + z§1, preferably with z = 0, x> 0.3 and y> 0.3 with a thickness of 0.4-4.9 μm, preferably 1, 5-4.0 μm with columnar grains, using preferably a moderate temperature CVD technique, MTCVD, (using acetonitrile as a carbon and nitrogen source to form the layer in the temperature range 700-900 ° C). The exact conditions depend to some extent on the design of the equipment used. a layer of TiCxNyO 2 (C) with x + y + z§1, preferably y> x and z <0.2, more preferably y> 0.8 and z = 0, with equal-axis grains with size <0.5 μm and a total thickness of 0.1 μm using known CVD methods. This layer (C) is omitted in a second embodiment.

- The total thickness of the layers A + B + C is 0.7-5.5 μm, preferably 1.2-5.0 μm. Preferably, layers A and C are each thinner than layer B. - a multilayer (D) consisting of a plurality of alternating Al 2 O 3 and TiCxNyO 2 layers (x + y + z <1), preferably k-Al 2 O 3 and TiN layers, with use of known CVD methods. The innermost and outermost layer of the multilayer sequence is Al 2 O 3 layer. The total number of layers, comprising both TiCxNyO 2 and Al 2 O 3 layers, is between 5 and 31, preferably 11 and 15 layers. The Al 2 O 3 layers have an individual layer thickness of <0.6 μm, preferably 0.2-0.5 μm.

The TiCxNyO 2 layers have an individual layer thickness of 0.01-0.2 μm, preferably 0.02-0.15 μm. The total thickness of the multilayer is 1.0-5.0 μm, preferably 1.5-4.0 μm. The grain size of the Al2O3 layer is equal to or less than the thickness of the Al2O3 layer. preferably, an outermost layer system (E) consisting of one or more layers in the order of TiCxNy (x + y51), preferably three to five layers in the order TiN, TiC and TiN, using known CVD methods. The total thickness is <2.0 μm.

The total thickness of the layers A + B + C + D + E is 2.0-9.0 μm.

The coating is mechanically post-treated to expose the multi-layer along the edge line by brushing, blasting, a grinding operation or combinations thereof so that the contact surfaces against the chip and workpiece have been treated on the tension and release side, respectively.

In the preferred method, two nylon brushes containing SiC grains are used with the set-up and fixing of the insert in such a way that with one mainly brushes its clamping side and with the other mainly its release side to achieve the desired properties on the cutting and release surface of the insert.

The removal of the outermost layer (E) at the edge line will expose the Al2O3 layer along the edge line. The edge line is defined as the edge-treated area of the insert. The untreated egg line is illustrated in Fig. 2.1 and the finished egg line is illustrated in Figs. 2.2 and 2.3. It is preferred that only the non-oxide topsheet and portions of the multilayer be removed. The TiCxNyO 2 layer (A + B + C) may, however, be visible on smaller parts of the edge line (Fig. 2.3).

Examples The following inserts and examples are chosen to exemplify the advantages of the invention.

The presented inserts have been tested under identical conditions in each example.

Insert A. Carbide rotary insert according to the invention with 6.0 wt% Co, 1.0 wt% Ti, 0.4 wt% Nb, 3.3 wt% Ta (Ti / (Ti + Ta + Nb) = 0.21), 0.05 wt% N and residual WC and with an average grain size of 2.8 μm and with a binder phase enriched and on cubic carbide depleted zone with a depth of 15 μm were coated with 0.5 μm TiN (innermost layer), 2.2 μm column Ti (C, N), and 0.5 μm equiaxed TiN, 2.2 μm (x-Al 2 O 3 + TiN) 6k-Al 2 O 3 multilayer and an outer layer of 0.5 μm TiN + TiC + TiN.

The coating was finished along the edge line with nylon brushes containing SiC grains. The outermost coating was removed a = 0.1 mm and b = 0.05 mm on the chip and release side.

Insert B. Carbide rotary insert according to the invention with 6.0 wt% Co, 1.0 wt% Ti, 0.4 wt% Nb, 3.3 wt% Ta (Ti / (Ti + Ta + Nb) = 0.2l), 0.05 wt% N and residual WC with an average grain size of 2.3 μm and with a binder phase-enriched and on cubic carbide depleted zone from the surface down to 15 μm was coated with 0.5 μm TiN (innermost layer), 2.2 μm column Ti (C, N), and 0.5 μm equiaxed TiN, 2.2 μm (k-Al 2 O 3 + TiN) 6k-Al 2 O 3 multilayer and an outer layer of 0.5 μm TiN + TiC + TiN. 10 Ü 20 25 30 35 40 (11 ht) * ~ 1 \ 1> C3 (I \ 9 The coating was finished along the edge line with nylon brushes containing SiC grains. The outermost coating was removed a = 0.1 mm and b = 0, 05 mm into the chip and release side.

Inserts C. Commercial cemented carbide rotary inserts with a substrate composition of 6.2 wt% Co, 2.3 wt% Ti, 2.0 wt% Nb, 0.1 wt% Ta (Ti / (Ti + Ta + Nb) = 0 , 52), 0.14 wt% N and residual WC. The average WC grain size is 2.7 μm and the substrate also has a binder phase-enriched and 7-phase depleted zone down to a depth of 26 μm from the surface. The coating consists of a 0.1 μm TiN innermost layer, 4.0 μm column Ti (C, N), 0.3 μm uniaxial TiN, 1.9 μm K-Al 2 O 3 and an outer layer of 0.3 μm TiN.

Inserts D. Commercial cemented carbide rotary inserts with a substrate composition of 6.0 wt% Co, 2.1 wt% Ti, 0.4 wt% Nb, 3.3 wt% Ta (Ti / (Ti + Ta + Nb) = 0 , 36), 0.09 wt% N and residual WC. The average WC grain size is 2.4 μm and the substrate also has a binder phase-enriched and y-phase depleted zone down to a depth of 13 μm from the surface. The coating consists of a 0.5 μm TiN innermost layer, 3.0 μm columnar Ti (C, N), 0.3 μm equiaxial TiN, 1.7 μm K-Al 2 O 3 and an outer layer of 0.3 μm TiN .

Inserts E. Commercial cemented carbide rotary inserts with 7.5 wt% Co, 2.72 wt% Ta, 0.44 wt% Nb, 1.83 wt% Ti (Ti / (Ti + Ta + Nb) = 0.37), 0 .09% by weight of N and residual WC with an average grain size of 2.0 μm and with a binder phase-enriched and a 26 cubic deep surface zone depleted in cubic carbide and coated with 0.5 μm TiN (innermost layer), 7.5 μm column Ti ( C, N), 1.2 μm a + K-Al 2 O 3 and an outer layer of 1.0 μm TiN.

The coating was post-treated along the edge line with nylon brushes containing SiC grains. The outermost coating was removed b = 0.1 mm in on the release side.

Inserts F. Commercial cemented carbide rotary inserts with 8.75 wt% Co, 1.15 wt% Ta, 0.27 wt% Nb, (Ti / (Ti + Ta + Nb) = 0), 0.09 wt% N and residual WC with an average grain size of 2.0 μm coated with 0.5 μm TiN (innermost layer), 2.2 μm column Ti (C, N), and 0.5 μm uniaxial TiN, 2.2 μm (K-Al 2 O 3 + TiN ) 5K-Al2O3 multilayer and an outermost layer of 0.5 μm TiN + TiC + TiN.

The coating was post-treated along the edge line with nylon brushes containing SiC grains. The outermost coating was removed a = 0.1 mm and b = 0.05 mm into the chip and the release page.

Example 1 Inserts from A and E were tested in a turning operation. uu m \: 1 v: c: G \ Operation: External longitudinal turning and planing of bars Working material: Austenitic stainless steel, AISI304L Cutting speed: 270 m / min Feed rate: 0.3 mm / Rotation Cutting depth: 2 mm Cutting type: CNMGl20408-MM Result : Lifespan Insert A: (invention) 9 min Insert E: (previously known) 5 min Comment: Lifetime criterion was maximum phase wear 0.3 mm from the edge line. Wear develops irregularly due to local plastic deformation. This example shows improvement in plastic deformation resistance of the insert according to the invention.

Example 2 Inserts from B and E were tested in a turning operation.

Operation: Longitudinal turning and planing of rod Working material: Austenitic stainless steel, AISI304L Cutting speed: 290 m / min Feed rate: 0.2 mm / revolution Cutting depth: 2 mm Cutting type: CNMG 120408-MM Result: Service life Cutting B: (invention) 17 min Cutting E: (previously known) 8 min Comment: Lifetime criterion was maximum phase wear 0.3 mm from the edge line in engagement. Wear develops irregularly due to local plastic deformation. This example shows the improvement in plastic deformation resistance of the insert according to the invention.

Example 3 Inserts from B, D and E were tested in a turning operation. 10 20 25 30 35 40 UH NJ \ J MD C) O \ ..- ... a Operation: Longitudinal turning and planing against shoulder Working material: Austenitic stainless steel, AISI304L Cutting speed: Feed: Cutting depth: Cutting styles: Result: Cutting B: (invention) Cutting D: (previously known) Cutting E: (previously known) 270 m / min 0.3 mm / revolution 2 mm CNMG 120408-MM Edge damage 0.2 mm / min 0.9 mm / min 0.2 mm / min Comment: The test is set to cause damage to the edge outside the direct contact surface between the tool and the workpiece, normally referred to as chip hammering and chip clamping. Resistance to such damage is directly related to edge toughness.

The insert according to the invention shows improvements in these respects. The edge toughness is increased (inserts B and D) or maintained (inserts B and E) at the same time as the plastic deformation resistance is increased (Example 2).

Example 4 Cuts from A and C were tested in a turning operation.

Operation: Planing to the center Workpiece material: Austenitic stainless steel, AISI304L Cutting speed: Feed: Cutting depth: Cutting type: Result: Cutting A: Cutting C: (invention) (previously known) 180 m / min 0.30 -> 0.15 mm / revolution 1 mm CNMG 120408-MM Lifespan 5 min 3 min Comment: This is an operation that requires edge toughness and the test shows clear improvement of the insert according to the invention compared to previously known inserts. However, it is difficult in this example to identify a simple critical wear, but it can be described as a combination of wear due to chipping, flaking of the coating on tension side and adhesive wear.

Example 5 Inserts from B and E were tested in a turning operation.

Operation: Shaft profiling Working material: Austenitic stainless steel, AISI316L Cutting speed: 200 m / min Feed rate: 0.25 mm / rev Cutting depth: 3 mm Cutting type: TNMG 160408-MM Result: Service life Cutting B: (invention) 14 details Cutting E: (previously known) 9 details Comment: This test shows improvement of edge toughness for the insert according to the invention compared to previously known inserts. Eggline chipping and beam wear occur earlier for the previously known Skäret.

Example 6 Inserts from A, E and F were tested in a turning operation.

Operation: Planing of a shaft Working material: Austenitic stainless steel, AISI304L Cutting speed: 180 m / min Feed rate: 0.30 -> 15 mm / revolution Cutting depth: 1 mm Cutting type: - CNMG 120408 ~ MM Result: Service life Cutting A: (invention) 6.5 min Insert E: (previously known) 2.5 min Insert F: (previously known) 5.5 min Comment: This example shows that the insert according to the invention has increased edge toughness. In this example, it is difficult to identify a simple critical wear, but it can be described as a combination of wear due to chipping, flaking of the coating on the chip side and adhesive wear.

Example 7 Cuts from B and E were tested in a turning operation.

Operation: Combined longitudinal turning and planing of a small bar.

Working material: Austenitic stainless steel, AISI 304L Cutting speed: 250 m / min Feed rate: 0.4 mm / revolution Cutting depth: 2 mm Cutting type: CNMG 120408-MM Result: Service life Cutting B: (invention) 8 min Cutting E: (previously known) 4 min Comment: The main wear mechanisms are plastic deformation and adhesive wear. This example shows an improvement in resistance regarding both of these mechanisms for the insert according to the invention compared with previously known inserts.

Example gel 8 Inserts from B and E were tested in a turning operation.

Operation: Continuous machining of a forged component Working material Austenitic stainless steel, SS2343 Cutting speed: 200 m / min Feed rate: 0.17-0.27 mm / revolution Cutting depth: 0.1 -1.3 mm Cutting type: cNMG1204o9-MM Result: Service life Cut B: (invention) 1500 details Cut E: (previously known) 200 details Comment: Critical wear criteria are flaking, loose edge formation and chipping. The insert according to the invention shows 10 (II Fx) * \ l \ 1) CD G \ 14 improved resistance to these types of wear compared with previously known inserts.

In summary, it can be stated that from the results of the examples above it is clear that by combining a cemented carbide substrate with the given composition, the choice of multilayer coating with specific thicknesses and the special edge treatment, an insert with excellent cutting performance has been created thereby. that it combines much of what was thought to be contradictory characteristics described in the introduction.

Claims (5)

10 20 25 30 35 40 U1 N) \ J Q) CD CI \ Krav A coated cemented carbide insert specially designed for stainless steel turning characterized by - a cemented carbide substrate having a composition comprising 5.0- <8.0 wt% Co, 3.0-8.0 wt% cubic carbides of the metals Ti, Ta and Nb and possibly other carbides of the elements from group IVb, Vb or Vïb of the periodic table, the Ti / (Ti + Ta + Nb) ratio being 0.05-0.3, 0.01-0 2% by weight of N and the remainder tungsten carbide (WC) having a grain size of 1,5-3,5 μm in the sintered state and having a y-phase depleted and binder phase-enriched surface zone having a depth of 5-30 μm, and a 2 0-9.0 μm, preferably 4.0-8.0 μm thick coating consisting of a first, innermost layer system consisting of - a first layer TiCxNyO 2 with x + y + zíl, preferably Y> X and z <0, 2, preferably y> 0.8 and z = 0, with equal-axis grains with size 0.1 μm, preferably 0.1-0.6 μm - a second layer of TiCxNyO 2 with x + y + z 1, preferably with z = 0 , x> 0.3 and y> 0.3, more preferably x> 0.5, with a thickness of 0.4-4.9 μm, preferably 1.5-4.0 pm with columnar grains - a third layer of TiCxNyOz with x + y + z§l, preferably y> x and z <0.2, preferably y> 0.8 and z = 0, with equilateral grains with size 0, 1 pm , preferably 0.2-0.8 μm wherein the total thickness of the innermost layer system is 0.7-5.5 μm, preferably 1.2-5.0 μm - a second multilayer system comprising from 5 to 31 alternating layers of K -Al2O3 and TiCxNyOz (x + y + z§l) wherein the innermost and outermost layers of the multilayer sequence are K-Al2O3 layers, K-Al2O3 layers with an individual layer thickness of <0.6 μm and the TiCxNyOz ~ layers from about 0.01 to about 0.2 μm with a total thickness of the multilayer from about 1.0 to about 5.0 μm, and wherein the multilayer is by mechanical finishing exposed along the edge line and into the chip and release side, such that the exposure on the chip side (a) is greater than about 0.03 and less than about 0.9 mm, the exposure on the release side (b) is greater than about 0.02 and less than about 0.2 mm and a> b. Insert according to claim 1, characterized in that said cemented carbide substrate having a composition comprising 5.0- <7.0% by weight of Co, 4.0-7.0% by weight of cubic carbides of the metals Ti, Ta and W N) \ JQ) CD C \ Nb and possibly other - or VIb of the periodic table, addition of elements forming cubic carbide so that the Ti / (Ti + Ta + Nb) ratio is 0.1-0.25, 0, 01 to 0.2% by weight of N and residual tungsten carbide (WC) having a grain size of 2.0 to 3.0 .mu.m in the sintered state and having a Y-phase depleted and binder phase-enriched surface zone having a depth of 5 to 25 .mu.m . The insert according to claim 1, characterized in that said second multilayer system comprises from about 11 to about 15 alternating layers of K-Al 2 O 3 and TiN, the K-Al 2 O 3 layers with an individual layer thickness of from about 0.2 to about 0 , 5 μm and TiN layers from about 0.02 to about 0.15 μm with a total thickness of the multilayer from about 1.5 to 4.0 μm. Cut according to any one of claims 1-3, characterized by an outermost layer system on top of the multilayer of one or more layers of TiCxNy (x + y§1), preferably three to five layers in sequence of TiN, TiC and TiN. Cutting according to one of Claims 1 to 4, characterized in that the multilayer and partly the innermost TiCxNyO 2 layer system are exposed along the edge line.