Surface coated cutting tools

Abstract

Providing a surface-coated cutting tool having excellent wear resistance and chipping resistance even in cutting various stainless steels 【Solution means】In order from the surface, a surface layer, TiO x (x = 1.3 to 1.5) oxide layer, Al2O3 layer, and lower layer, Only the cutting edge ridge line part exposes the Al2O3 layer, Taking the end on the rake face side of the cutting edge ridge line part where the Al2O3 layer is exposed as j = 0, from j = 0 to the rake face direction up to the nth closest to the cutting edge ridge line that coincides with the sum of the average thickness of the surface layer and the average thickness of the Ti oxide layer, When measuring the sum of the thickness of the surface layer and the thickness of the Ti oxide layer at n + 1 measurement points j with a measurement interval of 1 μm, t, which is the sum of the thickness of the surface layer and the thickness of the Ti oxide layer measured at the measurement point j j For Δt j+1 = t j+1 - t j (j = 0 to n - 1), the incremental rate Δt defined by j+1 is monotonically decreasing, and Δt j+1 is 0.02 to 0.10, and the maximum value of n is 1 to 20, a surface-coated cutting tool

Description

[Technical Field]

[0001] This invention relates to a surface-coated cutting tool (hereinafter sometimes referred to as a coated tool). [Background technology]

[0002] Conventionally, coated tools have been known in which a coating layer is formed on a substrate such as a tungsten carbide (hereinafter referred to as WC)-based cemented carbide. Furthermore, it has been proposed that by adjusting the composition and layer structure of this coating layer, coated tools with even better cutting performance can be obtained.

[0003] For example, Patent Document 1 describes a coated tool having a coating layer of TiCxNyOz or ZrCxNy on top of an α-Al2O3 layer, in which only the cutting edge of the coating layer exposes the α-Al2O3 layer. This coated tool is said to exhibit excellent flank wear resistance and crater wear resistance simultaneously, especially when working with low-carbon steel and stainless steel, and to exhibit high resistance to flaking of the coating, while also allowing the operator to easily distinguish the cutting edge in use with the naked eye.

[0004] Furthermore, for example, Patent Document 2 describes a coating layer having a total thickness of 2 to 50 μm, where the lower layer consists of at least one layer selected from titanium carbide, titanium nitride, titanium carbonitride, titanium carbonate, and aluminum oxide, and an outer layer of aluminum oxide with a thickness of 1 to 15 μm or a laminate of Al2O3 and ZrO2, with an intermediate layer being a TiO layer and a surface layer being TiC x N y O z , single-layer or multi-layer TiN, TiC, TiC x N y A coated tool is described in which one of the following conditions is met, and the surface layer has been removed from the cutting edge and rake face. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 8-52603 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-297585 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] The present invention has been made in view of the above circumstances and the above proposal, and an object thereof is to provide a surface-coated cutting tool that suppresses the occurrence of adhesion chipping and has excellent wear resistance and chipping resistance even when subjected to cutting of various stainless steels as well as steel and cast iron. [Means for Solving the Problems]

[0007] The surface-coated cutting tool according to an embodiment of the present invention has a substrate and a coating layer provided on the substrate, wherein the coating layer has a surface layer made of any one of TiN, TiC, TiCN, and TiNO having an average thickness of 0.20 to 0.50 μm, a TiO x (x = 1.3 to 1.5) titanium oxide layer having a composition represented by and having an average thickness of 0.20 to 1.50 μm below and in contact with the surface layer, an Al2O3 layer below and in contact with the titanium oxide layer, and a lower layer between the Al2O3 layer and the substrate, wherein only the cutting edge ridge line portion has the Al2O3 layer exposed, assuming that the end portion on the rake face side of the cutting edge ridge line portion where the Al2O3 layer is exposed is j = 0, from j = 0 to the n + 1 (n ≧ 1)th closest to the cutting edge ridge line that coincides with the sum of the average thickness of the surface layer and the average thickness of the titanium oxide layer in the rake face direction, when measuring the sum of the thickness of the surface layer and the thickness of the titanium oxide layer at n + 1 measurement points j with a measurement interval of 1 μm, t, which is the sum of the thickness of the surface layer and the thickness of the titanium oxide layer measured at the measurement point j j with respect to △t j+1 = tj+1 -t j (j = 0 to n - 1) defined increment rate Δt j+1 monotonically decreases, and the said Δt j+1 is 0.02 to 0.10, and the said Δt j+1 the maximum value of n that gives 0.02 to 0.10 is 1 to 20.

[0008] The surface-coated cutting tool according to the said embodiment may satisfy the following (1).

[0009] (1) The said lower layer is a TiCN layer and a TiN layer between the TiCN layer and the substrate.

Effect of the Invention

[0010] The surface-coated cutting tool according to the said embodiment, even when used for cutting various stainless steels etc. as well as steel and cast iron, suppresses the occurrence of adhesion chipping and exhibits excellent wear resistance and chipping resistance.

Brief Description of the Drawings

[0011] [Figure 1] It is a schematic diagram of the longitudinal section of the coating layer in the surface-coated cutting tool according to an embodiment of the present invention. [Figure 2] It is a schematic diagram showing that the thicknesses of the surface layer and the Ti oxide layer are continuously connected and gradually increase.

Mode for Carrying Out the Invention

[0012] The present inventor earnestly studied the coating layer, particularly the outermost surface layer, in order to obtain a cutting tool having excellent wear resistance even when used for high-speed cutting of various stainless steels etc. while ensuring the performance in cutting steel and cast iron.

[0013] As the surface layer of the coating layer, a coating layer having a relatively bright film color such as TiN may be formed so as to have wear resistance and be easy to distinguish before and after the use of the tool edge.

[0014] According to our research, a relatively light-colored surface layer such as TiN comes into direct contact with the workpiece. In particular, in cutting operations where the tool cutting edge becomes hot, such as high-speed cutting of stainless steel, the surface layer and the workpiece may adhere firmly (adhesion occurs), and the surface layer may peel off. In this case, in a coating layer where the surface layer and the underlying Al2O3 layer are firmly bonded, the Al2O3 layer peels off along with the surface layer, causing wear. Depending on the configuration of the coating layer between the Al2O3 layer and the substrate, the substrate may be exposed, thus impairing the durability of the coated tool.

[0015] Therefore, as described in prior art literature, it is conceivable to remove a relatively light-colored surface layer, such as the aforementioned TiN, from the cutting edge by machining. However, it is difficult to completely remove this surface layer by machining, and irregularities are unintentionally left on the surface layer. Then, when adhering material is pressed against this remaining surface layer during cutting, stress concentration occurs, and adhesive chipping occurs between the workpiece and the remaining surface layer.

[0016] The inventors conducted further studies to suppress the occurrence of this adhesive chipping. As a result, they found that a Ti oxide layer (TiO) is located directly beneath the surface layer. x We recognized that providing (x=1.3~1.5) suppresses the starting points of adhesive chipping. In other words, we derived the present invention from the following findings (1) to (3).

[0017] (1) Between the surface layer and the underlying Al2O3 layer is a Ti oxide layer (TiO x By providing (x=1.3~1.5), the surface layer of the cutting edge can be easily removed by machining, and the unintended remaining surface irregularities can be suppressed.

[0018] (2) Ti oxide layer (TiO x(x=1.3~1.5)) is highly tough, so it does not undergo brittle fracture during machining to remove the surface layer of the cutting edge. Furthermore, at the end of the cutting edge where the surface layer has been removed by machining, a structure can be achieved in which the surface layer, the Ti oxide layer, and the Al2O3 layer are smoothly and continuously connected.

[0019] (3) The smooth and continuously connected structure at the end of the cutting edge ridge of the cutting edge described in (2) can suppress the occurrence of adhesive chipping at the cutting edge ridge.

[0020] The present invention will be described below by providing a more detailed explanation of a covering tool according to an embodiment of the present invention. In this specification and the claims, when a numerical range is expressed using "M~N", it is synonymous with "M or greater, N or less", and the range includes the numerical values ​​of the upper limit (N) and the lower limit (M). Furthermore, when a unit is specified only for the upper limit (N), the upper limit (N) and the lower limit (M) have the same unit.

[0021] 1.Coating layer The coating layer consists of a surface layer, a Ti oxide layer, an Al2O3 layer, and a lower layer, arranged from the surface toward the substrate. Each layer will be described in order below.

[0022] (1) Surface layer The surface layer is a layer made of one of the following compounds: TiN, TiC, or TiCN, with an average thickness of 0.20 to 0.50 μm.

[0023] Surface layers composed of TiN, TiC, or TiCN compounds all possess wear resistance and a color that allows for sufficient identification of whether or not a coated tool is being used, and can therefore function as an identification layer. These surface layers may unintentionally contain oxygen due to the diffusion of oxygen from the Ti oxide layer, but this unintentional oxygen does not affect any of the physical properties.

[0024] The surface layer can function effectively as an identification layer when its average thickness is between 0.20 and 0.50 μm. However, if the average thickness exceeds 0.50 μm, the chipping resistance of the coating layer is impaired. The lower limit of the average thickness is sufficient to achieve the function of an identification layer, but in one example of the manufacturing method described later, the lower limit is 0.20 μm.

[0025] (2) Ti oxide layer The average thickness of the Ti oxide layer is 0.20 to 1.50 μm. This is because if the thickness is less than 0.20 μm, the diffusion of elements from the lower layer causes it to adhere firmly to the Al2O3 layer, making it difficult to remove the surface layer. If it exceeds 1.50 μm, the surface layer easily peels off when the coated tool is subjected to impact.

[0026] The Ti oxide layer is given by formula:TiO x It consists of Ti oxides with a composition expressed as (x=1.3~1.5). x If TiO is present beneath the surface layer, the surface layer at the cutting edge can be removed more easily than with weak machining. That is, when x is less than 1.3, x The Al2O3 layer adheres firmly to the Al2O3 layer, causing the Al2O3 layer to chip off during the removal of the surface layer at the edge of the cutting edge. If x exceeds 1.5, TiO x Because the material becomes brittle, when the cutting edge is treated to remove the surface layer and Ti oxide layer at the edge of the cutting edge, the Ti oxide layer undergoes brittle fracture, resulting in scattered surface layers and Ti oxide layers.

[0027] (3)Al2O3 layer There are no particular restrictions on the average thickness of the Al2O3 layer. However, there may be preferred average thicknesses depending on the type of workpiece and cutting conditions. For example, when performing high-speed cutting of various stainless steels, an average thickness of 1.00 to 3.00 μm may be preferable. This is because if the thickness is less than 1.00 μm, crater wear resistance decreases, and the tool may reach the end of its lifespan prematurely. If the thickness exceeds 3.00 μm, since the Al2O3 layer itself is a hard ceramic layer, large cracks proportional to the thickness of the layer may be introduced, resulting in insufficient fracture resistance.

[0028] (4) Lower layer The lower layer is the layer between the Al2O3 layer and the substrate, and may be a single layer or composed of two or more layers, with no particular restrictions on the compounds that make up each layer. The lower layer may consist of a TiCN layer and a TiN layer between the TiCN layer and the substrate. The average thicknesses of the TiCN layer and the TiN layer can be exemplified as 1.50 to 7.50 μm and 0.10 to 0.50 μm, respectively. Other examples of the lower layer include Ti carbonite, Ti carbonitride, and Al and Ti composite nitrides (carbonitrides).

[0029] (5) Unintended compounds The coating layer is formed in a manner that prevents the formation of compounds other than those mentioned above. However, slight disturbances in the deposition conditions (e.g., temperature changes, pressure changes, etc.) may unintentionally cause the partial formation of compounds other than those mentioned above (referred to as unintended compounds). Therefore, even if the claims and specification state that "layer A consists of compound X," layer A may contain these unintended compounds in addition to compound X. The presence of unintended compounds does not affect the physical properties of any of the layers constituting the coating layer, and the aforementioned problem is solved.

[0030] 2. Exposure of the Al2O3 layer at the cutting edge. The exposure of the Al2O3 layer at the edge of the cutting edge will be explained in detail below.

[0031] (1) Edge of the cutting edge The "cutting edge ridge" and "cutting edge ridge area" are defined as follows: As shown in Figure 1, the flank face (1) and the rake face (2) are approximated by straight lines, and the cutting edge ridge is found at the intersection point (3) where these two lines intersect when extended. From this cutting edge ridge, the shortest possible line segment is drawn toward the substrate surface. At the intersection of this line segment and the substrate surface, line segments of 20 to 80 μm, given by the honing process, are drawn perpendicular to this line segment in the direction of the flank face (1) and the rake face (2), respectively. The region (4) obtained by projecting this line segment toward the substrate surface parallel to the shortest possible line segment is called the substrate ridge area.

[0032] Here, before forming the coating layer on the cutting edge, the flank and rake faces may be honed to a thickness of 20-80 μm in each direction, depending on the shape of the tool substrate, in order to improve chipping resistance (the lengths of the honing treatment in the flank and rake faces do not have to be the same).

[0033] (2) Exposure of the Al2O3 layer The Al2O3 layer is exposed at the cutting edge (definition will be explained later). Therefore, it is possible to prevent the Al2O3 layer from peeling off along with the surface layer during cutting, causing wear, and, depending on the configuration of the coating layer between the Al2O3 layer and the substrate, the lower layer may also peel off, exposing the substrate and compromising the durability of the coated tool. Here, the Al2O3 layer does not need to be completely exposed at the cutting edge; the aforementioned problem can be solved even if the surface layer or the Ti oxide layer remains at a rate of up to 20% of the total area.

[0034] (3) Gradual increase rate of the thickness of the surface layer and the Ti oxide layer (△t n ) Let j=0 be the end of the rake face side of the cutting edge where the Al2O3 layer is exposed. From j=0, Up to the n+1 (n≧1)th edge closest to the cutting edge, where the sum of the average thickness of the surface layer and the average thickness of the Ti oxide layer coincides in the rake face direction. When measuring the sum of the surface layer thickness and the Ti oxide layer thickness at n+1 measurement points j with a measurement interval of 1 μm, t is the sum of the thickness of the surface layer and the thickness of the Ti oxide layer measured at measurement point j. j In contrast, △t j+1 =t j+1 -t j The rate of increase △t is defined by (j=0~n-1). j+1 teeth, It decreases monotonically, △t j+1 0.02 to 0.10, and △t j+1 It is preferable that the maximum n that gives a value of 0.02 to 0.10 is 1 to 20, that is, the distance L from the rake face side end of the cutting edge is 1 to 20 μm (L = n × 1 μm).

[0035] Here, monotonically decreasing means Δt j+1 This means that it does not increase (△t j+1 (It is also possible that all values ​​are the same.) Furthermore, the sum of the average thickness of the surface layer and the average thickness of the Ti oxide layer is said to be equal to the sum of the thickness of the surface layer and the thickness of the Ti oxide layer at n+1 measurement points j if the following relationship is satisfied. That is, |(Sum of the average thickness of the surface layer and the average thickness of the Ti oxide layer) - (Sum of the thickness of the surface layer and the thickness of the Ti oxide layer at n+1 measurement points j)| ≤ 0.01 (μm) That is the case.

[0036] △t j+1 The reason why the value of △t is between 0.02 and 0.10 is as follows: j+1 When △t is less than 0.02, the gradual increase disappears and the chipping resistance deteriorates. j+1 When the value exceeds 0.10, the thickness of the surface layer changes abruptly at the cutting edge, causing stress to concentrate in the surface layer near the machined cutting edge, resulting in a deterioration of chipping resistance.

[0037] Furthermore, the reason why the maximum value of n is set to 1 to 20 and the distance L from the rake face end of the cutting edge is set to 1 to 20 μm (L = n × 1 μm) is as follows: When L is less than 1 μm, the thickness of the surface layer changes abruptly at the cutting edge, and this abrupt change makes it easy for stress to concentrate in the surface layer, degrading chipping resistance. On the other hand, when L exceeds 20 μm, there is a region near the cutting edge where the thickness of the surface layer becomes extremely thin, so wear resistance of the surface layer cannot be obtained.

[0038] Furthermore, this △t j The state where the value is 0.02 to 0.10 is a state in which the thickness of the surface layer and the Ti oxide layer increases continuously and gradually, as shown in Figure 2. The distance L from the rake face side end of the cutting edge ridge in this state in which the thickness of the surface layer and the Ti oxide layer increases continuously and gradually is defined as L.

[0039] 3.Base (1) Composition The substrate is a WC-based cemented carbide. A WC-based cemented carbide is a alloy in which iron group elements such as Co are used as the bonding phase component, and W carbides (not limited to stoichiometric composition) are the main component of the hard phase component, and may also contain one or more carbides of Cr, Ti, Ta, Nb, and Zr (not limited to stoichiometric composition).

[0040] (2) Shape The shape of the base material is not particularly restricted as long as it is a shape that can be used as a cutting tool; examples include the shape of an insert and the shape of a drill.

[0041] 4.Measurement method Next, I will explain the measurement method.

[0042] (1) Average thickness of each layer The average thickness of each layer constituting the coating layer can be obtained, for example, by preparing a sample for observation by cutting the coating layer in a longitudinal section at an arbitrary position (a section perpendicular to the substrate surface, treated as if there were no minute irregularities on the substrate surface) using a focused ion beam system (FIB), and then observing the longitudinal section at multiple locations (e.g., 5 locations) using a scanning electron microscope (SEM), transmission electron microscope (TEM), scanning transmission electron microscope (STEM), or energy dispersive X-ray spectrometry (EDX) device attached to an SEM or TEM to identify each layer, measure the thickness of each layer, and average the result.

[0043] In determining the average thickness, the substrate surface, which serves as the starting point for the length in the thickness direction, is defined as the reference line of the interface roughness between the substrate and the coating layer in an observation image of a longitudinal section (approximately in the thickness direction) perpendicular to the substrate. That is, when the substrate has a planar surface such as an insert, elemental mapping using EDS is performed on the longitudinal section, and the interface between the coating layer and the substrate is determined by performing known image processing on the obtained elemental map. The average line y0 is then arithmetically calculated for the roughness curve of the interface between the coating layer and the substrate, and this is taken as the surface of the substrate.

[0044] (2) Composition of the Ti oxide layer The composition of the Ti oxide layer can be obtained by observing it at multiple locations (e.g., 5 locations) using TEM-EDS, measuring the composition at each location, and then taking the arithmetic mean of the results.

[0045] (3) Gradual increase rate (△t n ) and distance (L) The following procedure will determine the rate of increase (△t) n Find the distance (L) between ( ) and ( ).

[0046] 1) Create a cross-section perpendicular to the flank surface of the coated tool by mechanical polishing using a diamond grinding wheel or the like.

[0047] 2) Starting from the rake face end of the cutting edge where the Al2O3 layer is exposed (j=0), the sum of the surface layer thickness and the Ti oxide layer thickness is calculated at 1 μm intervals along the surface of the coated tool in the direction of the rake face. The measurement is continued until the n+1 (n≧1) point closest to the cutting edge where the sum of the separately measured average thickness of the surface layer and the average thickness of the Ti oxide layer matches.

[0048] 3) The distance from the starting point is plotted on the horizontal axis, and the sum of the thickness of the surface layer and the thickness of the Ti oxide layer at the distance from the starting point is plotted on the vertical axis.

[0049] 4) The sum of the thickness of the surface layer and the thickness of the Ti oxide layer at the j-th (j μm) distance from the starting point is t j In this case, the t at a distance of jμm from the starting point j+1 The rate of increase (slope) △t j+1 =( t j+1 -t j Calculate ).

[0050] 5) The slope from the starting point (△t j+1 The distance (the maximum value of n) where n exceeds 0.02 is taken as the value of the interval L (L = n × 1 μm).

[0051] 5. Manufacturing method As an example of a manufacturing method for an embodiment in which the lower layer is a TiCN layer and a TiN layer between the TiCN layer and the substrate, the following CVD method can be used.

[0052] (1) Film deposition conditions The film deposition conditions are as follows. The percentages in the gas composition below are by volume.

[0053] 1)TiN layer (lower layer) Gas composition: TiCl4: 2.0-5.0%, N2: 25.0-35.0%, H2: residual Pressure 4.0~30.0 kPa Temperature 850~1050℃ Deposition time: 5-15 minutes

[0054] 2)TiCN layer (lower layer) Gas composition: TiCl4: 1.0-2.0%, CH3CN: 0.1-1.0% N2: 30.0~40.0%, H2: remaining Pressure 5.0~7.0 kPa Temperature 850~950℃ Deposition time: 50-70 minutes

[0055] 3)Al2O3 layer Gas composition: AlCl3: 1.0-3.0%, CO2: 4.5-6.5% HCl: 1.0~4.0%, H2S: 0.1~0.3%, H2: remainder Pressure 4.0~30.0 kPa Temperature 850~1050℃ Deposition time: 100-130 minutes

[0056] 4) Ti oxide layer Gas composition: TiCl4: 1.0-1.5%, CO2: 0.3-0.7%, Ar: 35.0-45.0%, H2: residual Pressure 4.0~30.0 kPa Temperature 850~1050℃ Deposition time: 5-15 minutes

[0057] 5)TiN layer (surface layer) Gas composition: TiCl4: 2.0-5.0%, N2: 25.0-35.0%, H2: residual Pressure 4.0~30.0 kPa Temperature 850~1050℃ Deposition time: 10-40 minutes

[0058] 6)TiCN (surface layer) Gas composition: TiCl4: 4.0-7.0%, CH3CN: 0.1-1.0% N2: 25.0~35.0%, H2: remaining Pressure 20.0~50.0 kPa Temperature 900~1050℃ Deposition time: 10-40 minutes

[0059] 7)TiC (surface layer) Gas composition: TiCl4: 2.0-5.0%, CH4: 1.0-4.0%, H2: residual Pressure 10.0~60.0 kPa Temperature 1000~1150℃ Deposition time: 10-30 minutes

[0060] (2) Treatment of the cutting edge ridge The edge of the cutting edge is polished using an industrial brush made of synthetic fibers such as polypropylene resin, starting from the rake face and moving towards the edge. Examples of processing conditions include the following: Brush rotation speed: 300-600 min ―1 Carrier rotation speed: 20-80 min ―1 Brush contact width at the blade tip: 0.4~0.8mm Brush insertion depth from the scooping surface direction: 0.2~0.8mm Processing time: 20~40 seconds [Examples]

[0061] Next, we will describe some examples. As an example, we will describe its application to a coated tool with an insert shape using a WC-based cemented carbide as the base material, but the shape of the base material may be a drill, end mill, etc., as mentioned above.

[0062] 1. Preparation of the substrate Co powder, TiC powder, TaC powder, NbC powder, ZrC powder, Cr3C2 powder, and WC powder were prepared as raw material powders. These raw material powders were blended according to the formulation shown in Table 1, and wax was added. The mixture was then wet-mixed in a ball mill for 72 hours, dried under reduced pressure, and then press-molded at a pressure of 150 MPa. These compacted bodies were sintered and processed to the specified dimensions to create substrates A to C with insert shapes conforming to the ISO standard CNMG120408. Note that each raw material powder contained trace amounts of unavoidable impurities.

[0063] 2. Film formation The lower layer and Al2O3 layer were deposited under the conditions shown in Table 2, and the Ti oxide layer and surface layer were deposited under the conditions shown in Tables 3 and 4. Furthermore, the cutting edge was machined under the conditions shown in Table 5 to produce coated tools 1 to 10 of the examples shown in Table 6 (hereinafter referred to as Examples).

[0064] In contrast, as comparative examples, coating tools 1 to 8 (hereinafter referred to as comparative examples) shown in Table 6 were prepared using the film deposition conditions in Tables 2, 3, and 4, and the cutting edge processing shown in Table 5.

[0065] [Table 1]

[0066] In Table 1, "-" indicates that the ingredient was not included.

[0067] [Table 2]

[0068] [Table 3]

[0069] [Table 4]

[0070] [Table 5]

[0071] [Table 6]

[0072] In Table 6, because Comparative Example 7 did not have a machined edge at the cutting edge, it was not possible to measure the section where the layer thickness gradually increases and the rate of gradual increase at the cutting edge.

[0073] Next, the following cutting tests were performed on Examples 1-10 and Comparative Examples 1-8, and the flank wear width and the presence or absence of chipping were checked at 1-minute intervals. The results are shown in Table 7.

[0074] Cutting test Workpiece material: Continuous machining of the outer diameter of a Φ200 round bar made of SUS304. Cutting speed: 150m / min Cut: 1.5mm Feed rate: 0.3mm / rev Cutting time: 50min

[0075] Every minute after the start of the cutting test, the presence or absence of chipping and delamination caused by chipping was visually observed, and the flank wear width was measured. Measurements were taken every minute, and the lifespan was defined as the point at which the flank wear width first exceeded 0.3 mm.

[0076] [Table 7]

[0077] In Table 7, the comparative example reached the end of its service life (chipping occurred) before the specified cutting time in the cutting test, so the time (minutes) at which it reached the end of its service life is shown.

[0078] As is clear from Table 7, in all of the examples, the wear width of the flank surface was small and no chipping occurred. However, in the comparative example, the wear width of the flank surface was large and chipping occurred. This demonstrates that all of the examples exhibit excellent wear resistance and chipping resistance even when subjected to cutting processes for stainless steel. [Explanation of symbols]

[0079] 1. Escape 2 Scoop surface 3. Edge of the blade 4. Edge of the cutting edge 5 Surface layer 6 Ti oxide layer 7 Al2O3 layers

Claims

1. A surface-coated cutting tool having a substrate and a coating layer provided on the substrate, The aforementioned coating layer is A surface layer consisting of one of the following compounds: TiN, TiC, TiCN, or TiNO, with an average thickness of 0.20 to 0.50 μm, In contact with the aforementioned surface layer and below it is a layer with an average thickness of 0.20 to 1.50 μm, based on the formula: TiO ｘ A Ti oxide layer with a composition expressed as (x = 1.3 to 1.5), Al, which is in contact with the Ti oxide layer and located below it. ２ O ３ Layers, The aforementioned Al ２ O ３ It consists of a layer and a lower layer between the substrate, Only the cutting edge ridge portion of the aforementioned Al ２ O ３ The layer is exposed. The above-mentioned Al ２ O ３ Taking the end on the rake face side of the cutting edge ridge line portion where the above-mentioned Al O layer is exposed as j = 0, from j = 0 to the nth (n ≧ 1) closest to the cutting edge ridge line that coincides with the sum of the average thickness of the surface layer and the average thickness of the Ti oxide layer in the rake face direction, When measuring the sum of the thickness of the surface layer and the thickness of the Ti oxide layer at n+1 measurement points j with a measurement interval of 1 μm, t is the sum of the thickness of the surface layer and the thickness of the Ti oxide layer, as measured at the aforementioned measurement point j. ｊ In contrast, △t ｊ＋１ = t ｊ＋１ -t ｊ The rate of increase Δt is defined by (j = 0 to n-1). ｊ＋１ It decreases monotonically, and the Δt ｊ＋１ is 0.02 to 0.10, and the above △t ｊ＋１ The maximum value of n that gives 0.02 to 0.10 is 1 to 20. A surface-coated cutting tool characterized by the following features.

2. The surface-coated cutting tool according to claim 1, characterized in that the lower layer is a TiCN layer and a TiN layer between the TiCN layer and the substrate.

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