A soft-hard multi-element coating composite microstructure milling cutter for cutting nickel-based superalloy

Abstract

The application discloses a soft-hard multi-element coating composite microstructure milling cutter for cutting nickel-based high-temperature alloy. The milling cutter comprises a rake face, the edge of the rake face is a main cutting edge, a crescent-shaped micro groove is arranged on the cutting edge near a corner of the main cutting edge, the bottom of the micro groove is a concave curved surface, and the outer contour of the micro groove on the rake face is composed of four circular arcs which are smoothly connected, wherein: the circular arc segment II and the circular arc segment IV are arranged from inside to outside on the rake face, both are convex to the corner of the main cutting edge, the circular arc segment II and the circular arc segment IV are tangent to the circular arc segment I near the short side of the rake face, and are tangent to the circular arc segment III near the long side of the rake face; a small micron scale texture array is designed on the circular arc segment IV of the micro groove; and the surface of the rake face is sequentially stacked from bottom to top with a Cr transition layer, an AlCrN hard coating layer and a WS2 soft coating layer. The milling cutter has the characteristics of reducing cutting force and cutting temperature and improving the anti-damage performance of the cutter.

Description

Technical Field

[0001] This invention relates to a cutting tool for use in the field of cutting processing, and in particular to a soft and hard multi-coated composite microstructure milling cutter for cutting nickel-based superalloys. Background Technology

[0002] High-temperature alloys, due to their high strength and low thermal conductivity, are prone to problems during machining, such as tool adhesion, high tool-chip interface temperature, and low tool wear resistance. These problems significantly shorten tool life. Tool wear, a normal phenomenon of tool failure, typically occurs on the rake and flank faces. Near-field breakage at the cutting edge is a significant form of tool failure, primarily occurring with brittle tools, in interrupted cutting processes, or in the machining of high-hardness, high-strength materials. Furthermore, during milling, the tool temperature rises sharply, which not only reduces tool durability but also lowers machining quality. Currently, cutting fluids are commonly used to lower cutting temperatures, but this leads to increased manufacturing costs and environmental pollution. Summary of the Invention

[0003] This invention provides a soft-hard multi-coated composite microstructure milling cutter for cutting nickel-based superalloys. This invention features reduced cutting temperature and improved tool durability.

[0004] The technical solution of this invention: A soft and hard multi-coated composite microstructure milling cutter for cutting nickel-based high-temperature alloys includes a rake face, the edge of which is the main cutting edge. A crescent-shaped microgroove is placed in the near-field of the main cutting edge at the corner of the rake face. The bottom of the microgroove is a concave curved surface. The outer contour of the microgroove on the rake face is composed of four smoothly connected arc segments. Among them, arc segments II and IV are arranged from the inside to the outside on the rake face and are convex towards the corner of the main cutting edge. The side of arc segments II and IV near the short side of the rake face is tangent to arc segment I, and the side of arc segments II and IV near the long side of the rake face is tangent to arc segment III. A micron-scale texture array is designed along the arc segment IV of the microgroove. The microgroove and the micron-scale texture array together constitute the composite microstructure. The rake face and the surface of the composite microstructure are sequentially stacked from bottom to top with a Cr transition layer, an AlCrN hard coating, and a WS2 soft coating.

[0005] In the aforementioned soft and hard multi-coated composite microstructure milling cutter for cutting nickel-based superalloys, the micron-scale texture array includes one or more parallel rectangular grooves. The parallel rectangular grooves form an overall convex structure towards the corner of the main cutting edge based on the curvature of the arc segment IV.

[0006] In the aforementioned soft and hard multi-element coating composite microstructure milling cutter for cutting nickel-based superalloys, in the micron-scale texture array, the length of the rectangular groove L = 0.1~0.3mm, preferably 0.2mm, the width of the rectangular groove W = 0.03~0.05mm, preferably 0.045mm, the depth of the rectangular groove D1 = 0.05~0.15mm, preferably 0.1mm, the distance between the relative long sides of adjacent rectangular grooves S = 0.03~0.05mm, preferably 0.04mm, and the included angle θ between the long side of the rectangular groove and the outer edge of the main cutting edge near the arc segment I at the corner = 55°~65°, preferably 60°.

[0007] In the aforementioned soft and hard multi-coated composite microstructure milling cutter for cutting nickel-based superalloys, the radii R1 to R4 of the arc segments I to IV have the following relationship: R2 > R4 > R1 > R3.

[0008] In the aforementioned soft and hard multi-coated composite microstructure milling cutter for cutting nickel-based superalloys, the radii R1 to R4 of the arc segments I to IV are respectively R1 = 0.1 to 0.3 mm, preferably 0.2 mm, R2 = 1.6 to 1.8 mm, preferably 1.723 mm, R3 = 0.1 to 0.2 mm, preferably 0.15 mm, and R4 = 1 to 2 mm, preferably 1 mm.

[0009] In the aforementioned composite microstructure milling cutter with soft and hard multi-element coating for cutting nickel-based superalloys, the distance L1 from the tangent point of arc segments III and IV to the outer edge of the main cutting edge near arc segment III at the corner is 0.1-0.2 mm, preferably 0.15 mm; the distance L2 from the tangent point of arc segments I and IV to the outer edge of the main cutting edge near arc segment I at the corner is 0.1-0.2 mm, preferably 0.12 mm; the distance W1 between the two tangent points of arc segment I and arc segments II and IV is 0.2-0.4 mm, preferably 0.395 mm; the maximum width W2 between arc segments II and IV is 0.4-0.5 mm, preferably 0.487 mm; the distance W3 between the two tangent points of arc segment III and arc segments II and IV is 0.1-0.3 mm, preferably 0.29 mm; and the maximum depth D of the microgroove is 0.1-0.2 mm, preferably 0.1 mm.

[0010] In the aforementioned soft and hard multi-coated composite microstructure end mill for cutting nickel-based superalloys, the thickness of the Cr transition layer is 0.5–1 μm, the thickness of the AlCrN hard coating is 2–4 μm (preferably 3 μm), and the thickness of the WS2 soft coating is 1–3 μm (preferably 2 μm).

[0011] Beneficial effects: This invention adds a coating material to the surface of the cutting tool and implants microstructures into the tool surface. Comparative simulation experiments comparing the original cutting tool with the original tool implanted with the composite microstructure are shown below. Figures 5-6As shown, the composite microstructure effectively reduces the cutting temperature during machining. The soft and hard multi-element coating thickness was selected using ANSYS finite element analysis. During the tool coating preparation process, different parameters of the coating material lead to different residual thermal stresses at the interface between the coating and the tool. Excessive residual thermal stress affects the adhesion between the coating and the tool substrate. Therefore, the simulation uses the maximum equivalent residual thermal stress between different coating material thicknesses and the milling cutter substrate as the evaluation index. (See [link to simulation]). Figures 7-12 The invention designs a soft-hard composite coating to achieve a suitable coating thickness and structure that matches the end mill substrate. This structure significantly improves the cutting performance of the tool. Specifically, the invention incorporates a meniscus microgroove structure near the cutting edge on the rake face of the end mill, along with a small micron-scale texture array designed along the microgroove edge. This composite microstructure shortens the actual contact length between the tool and the chip. Since the cutting force is positively correlated with the contact length, the composite microstructure effectively reduces the cutting force. Simultaneously, the composite microstructure forms a local stress buffer zone in the rake face region, weakening the direct impact of the chip on the tool edge and reducing the risk of rapid coating peeling during cutting. The WS2 soft coating, with its excellent friction-reducing and lubricating properties, further improves the friction state, while the AlCrN hard coating, with its high hardness and wear resistance, resists high contact stress, abrasive wear, and thermal shock during cutting, protecting the composite microstructure from collapse and rapid wear under high loads.

[0012] In this invention, the inventors unexpectedly discovered through extensive experiments cutting nickel-based superalloys that the composite microstructure of this invention, in conjunction with the Cr transition layer, AlCrN hard coating, and WS2 soft coating layer stacked sequentially from bottom to top, enables the end mill to achieve the lowest cutting force and cutting temperature when cutting nickel-based superalloys. This is mainly because: 1) The area near the cutting edge of the end mill is a region of stress and temperature concentration. The composite microstructure can reduce the contact stress near the cutting edge at a microscale, reducing chip adhesion. Furthermore, the composite microstructure can store lubricating media and accommodate chips, preventing secondary plowing between the chip and the workpiece, thereby reducing additional friction and extrusion deformation during cutting. The AlCrN hard coating has high hardness, wear resistance, and thermal stability. These characteristics provide better support for the soft coating and composite microstructure while protecting the tool substrate, making the tool less prone to severe wear, softening, or coating peeling under high-speed friction and high-temperature impact. The WS2 soft coating can reduce the friction coefficient between the tool and the chip, thus achieving the effect of reducing cutting force. 2) The composite microstructure of the rake face of the milling cutter can change the original continuous large-area contact state between the tool and the chip into a local intermittent contact state. The presence of the WS2 soft coating can reduce frictional resistance and give the tool a better lubrication effect, thereby reducing the generation of frictional heat between the tool and the chip and reducing the accumulation of cutting heat in local areas. At the same time, the AlCrN hard coating has thermal stability and can reduce the wear of the tool surface caused by high temperature, thus reducing the cutting temperature.

[0013] In actual production, the composite microstructure of this invention also possesses anti-breakage properties: the hard coating in the soft-hard multi-coated composite microstructure tool improves the surface hardness and wear resistance of the tool, while the soft coating buffers impact loads and reduces stress concentration in the tool tip area during cutting, lowering the risk of chipping and coating cracking. The composite microstructure further reduces thermomechanical coupling damage to the tool surface by reducing the contact area between the tool and chips, lowering the coefficient of friction, reducing the accumulation of cutting heat, and improving surface stress distribution. Because the toughening effect of the soft-hard composite coating and the friction-reducing and cooling effect of the composite microstructure work synergistically, the tool can effectively inhibit crack initiation and propagation during cutting, reducing coating peeling and tool tip breakage, thus exhibiting excellent anti-breakage performance.

[0014] To better demonstrate the beneficial effects of this invention, the inventors conducted the following experiments: A milling experimental platform was built to compare and analyze the milling of nickel-based superalloys under different cutting parameters using the original milling cutter (named T-CT milling cutter, TiAlN coated milling cutter), the original TiAlN coated microgroove milling cutter (named T-MST milling cutter), and the soft-hard multi-element coating composite microstructure milling cutter of this invention (named AW-CMST milling cutter), i.e., the milling cutter of Example 1. Each set of comparative experiments for all the milling cutters mentioned above was conducted under the same cutting conditions (cutting parameters, tool geometry, tool and workpiece materials, etc.), with a fixed milling depth ap of 0.3 mm and a milling width ae of 10 mm. The comparative milling experimental schemes and results for cutting nickel-based superalloys are shown in Tables 1 and 2.

[0015] Table 1 Milling Experiment Results

[0016] In summary, the milling cutter of the present invention has significant effects in reducing cutting force and cooling temperature.

[0017] Table 2 Comparison of surface roughness results Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 yes Figure 1 Enlarged view and schematic diagram of the microstructure at point M; Figure 3 This is a schematic diagram of the microgroove structure on the rake face; Figure 4 This is a schematic diagram of the structure of a soft and hard multi-element coating; Figure 5 This is a simulation diagram of the highest temperature of the original milling cutter when n=1000m / min and f=0.2mm; Figure 6 This is a simulation diagram of the highest temperature of the original end mill implanted with a composite microstructure without soft and hard multi-element coating when n=1000m / min and f=0.2mm. Figure 7 This is a cloud diagram of the equivalent residual thermal stress for an AlCrN hard coating with a thickness of 6 μm; Figure 8 This is a cloud diagram of the equivalent residual thermal stress for an AlCrN hard coating with a thickness of 4 μm; Figure 9 This is a cloud diagram of the equivalent residual thermal stress for an AlCrN hard coating with a thickness of 3 μm; Figure 10 This is an equivalent residual thermal stress cloud diagram for a WS2 soft coating with a coating thickness of 5μm; Figure 11This is a cloud diagram of the equivalent residual thermal stress of the WS2 soft coating with a coating thickness of 3μm; Figure 12 This is the equivalent residual thermal stress cloud diagram for a WS2 soft coating with a coating thickness of 2μm. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0020] Example 1. A soft-hard multi-coated composite microstructure milling cutter for cutting nickel-based superalloys, see [link to example]. Figures 1-4 The system includes a rake face 1, the edge of which is the main cutting edge 2. A crescent-shaped microgroove 3 is placed in the near-cutting edge region 5 at the corner of the main cutting edge 2 on the rake face 1. The bottom of the microgroove 3 is a concave curved surface. The outer contour of the microgroove 3 on the rake face is composed of four smoothly connected arc segments. Among them, arc segments II and IV are arranged from the inside to the outside on the rake face 1 and are convex towards the corner of the main cutting edge 2. The side of arc segments II and IV closest to the short side of the rake face 1 is tangent to arc segment I, and the side of arc segments III closest to the long side of the rake face 1 is tangent to arc segment III. The microgroove 3 is designed with a micron-scale texture array 4 along the arc segment IV. The microgroove 3 and the micron-scale texture array 4 together constitute a composite microstructure. The rake face 1 and the surface of the composite microstructure are layered from bottom to top with a Cr transition layer 7, an AlCrN hard coating 9, and a WS2 soft coating 8.

[0021] The aforementioned micron-scale texture array 4 includes one or more parallel rectangular slots, which form an overall convex structure towards the corner of the main cutting edge 2 based on the curvature of the circular arc segment IV.

[0022] In the aforementioned micron-scale textured array 4, the length of the rectangular groove L = 0.2 mm, the width of the rectangular groove W = 0.045 mm, the depth of the rectangular groove D1 = 0.1 mm, the distance between the relative long sides of adjacent rectangular grooves S = 0.04 mm, and the angle θ between the long side of the rectangular groove and the outer edge 6 of the main cutting edge near the arc segment I at the corner is 60°.

[0023] The radii R1 to R4 of the aforementioned circular arc segments I to IV have the following relationship: R2 > R4 > R1 > R3.

[0024] The radii R1 to R4 of the aforementioned arc segments I to IV are R1 = 0.2 mm, R2 = 1.723 mm, R3 = 0.15 mm, and R4 = 1 mm, respectively.

[0025] The distance L1 from the tangent point of the aforementioned arc segments III and IV to the outer edge 6 of the main cutting edge near arc segment III at the corner is 0.15 mm; the distance L2 from the tangent point of arc segments I and IV to the outer edge 6 of the main cutting edge near arc segment I at the corner is 0.12 mm; the distance W1 between the two tangent points of arc segment I and arc segments II and IV is 0.395 mm; the maximum width between arc segments II and IV is W2 = 0.487 mm; the distance W3 between the two tangent points of arc segment III and arc segments II and IV is 0.29 mm; the maximum depth D of the concavity of the microgroove 3 is 0.1 mm.

[0026] The aforementioned Cr transition layer 7 has a thickness of 0.5–1 μm, the AlCrN hard coating layer 9 has a thickness of 3 μm, and the WS2 soft coating layer 8 has a thickness of 2 μm.

Claims

1. A soft-hard multi-coated composite microstructure milling cutter for cutting nickel-based superalloys, characterized in that, The tool includes a rake face (1), the edge of which is the main cutting edge (2). A crescent-shaped micro-groove (3) is placed in the near-field (5) of the main cutting edge (2) at the corner of the rake face (1). The bottom of the micro-groove (3) is a concave surface. The outer contour of the micro-groove (3) on the rake face is composed of four smoothly connected arcs. Among them, arc segments II and IV are arranged from the inside to the outside on the rake face (1) and both convex towards the corner of the main cutting edge (2). The short side of the front face (1) is tangent to the arc segment I, and the long side of the front face (1) is tangent to the arc segment III. The microgroove (3) is designed with a micron-scale texture array (4) along the arc segment IV. The microgroove (3) and the micron-scale texture array (4) together constitute a composite microstructure. The front face (1) and the surface of the composite microstructure are layered from bottom to top with a Cr transition layer (7), an AlCrN hard coating (9), and a WS2 soft coating (8).

2. The soft and hard multi-component coated composite microstructure milling cutter for cutting nickel-based superalloys according to claim 1, characterized in that, The micron-scale texture array (4) includes one or more parallel rectangular slots, which form an overall convex structure towards the corner of the main cutting edge (2) based on the curvature of the arc segment IV.

3. The soft and hard multi-component coated composite microstructure milling cutter for cutting nickel-based superalloys according to claim 2, characterized in that, In the micron-scale texture array (4), the length L of the rectangular groove is 0.1 to 0.3 mm, the width W of the rectangular groove is 0.03 to 0.05 mm, the depth D1 of the rectangular groove is 0.05 to 0.15 mm, the distance S between the relative long sides of adjacent rectangular grooves is 0.03 to 0.05 mm, and the angle θ between the long side of the rectangular groove and the outer edge (6) of the main cutting edge near the arc segment I at the corner is 55° to 65°.

4. The soft and hard multi-component coated composite microstructure milling cutter for cutting nickel-based superalloys according to claim 1, characterized in that, The radii R1 to R4 of the circular arc segments I to IV have the following relationship: R2 > R4 > R1 > R3.

5. The soft and hard multi-component coated composite microstructure milling cutter for cutting nickel-based superalloys according to claim 1, characterized in that, The radii R1 to R4 of the arc segments I to IV are R1 = 0.1 to 0.3 mm, R2 = 1.6 to 1.8 mm, R3 = 0.1 to 0.2 mm, and R4 = 1 to 2 mm, respectively.

6. The soft and hard multi-component coated composite microstructure milling cutter for cutting nickel-based superalloys according to claim 1, characterized in that, The distance L1 between the tangent points of arc segments III and IV and the outer edge (6) of the main cutting edge near arc segment III at the corner is 0.1-0.2 mm; the distance L2 between the tangent points of arc segments I and IV and the outer edge (6) of the main cutting edge near arc segment I at the corner is 0.1-0.2 mm; the distance W1 between the two tangent points of arc segment I and arc segments II and IV is 0.2-0.4 mm; the maximum width W2 between arc segments II and IV is 0.4-0.5 mm; the distance W3 between the two tangent points of arc segment III and arc segments II and IV is 0.1-0.3 mm; the maximum depth D of the concavity of the microgroove (3) is 0.1-0.2 mm.

7. The soft and hard multi-component coated composite microstructure milling cutter for cutting nickel-based superalloys according to claim 1, characterized in that, The thickness of the Cr transition layer (7) is 0.5-1 μm, the thickness of the AlCrN hard coating (9) is 2-4 μm, and the thickness of the WS2 soft coating (8) is 1-3 μm.

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