Method for improving fatigue life of metal parts after preparation of hard coating and surface structure

Abstract

A method for improving the fatigue life of a metal component after preparation of a hard coating and a metal component surface structure for improving the fatigue life of the metal component, the method comprising the following steps: (1) before preparing the hard coating, applying a strengthening technique to strengthen the metal component substrate, so that a compressive stress strengthening layer with a compressive stress state is formed on the surface of the metal component; and (2) applying a coating preparation technique to prepare a hard coating on the surface of the strengthened metal component substrate. The present invention can improve the fatigue life of the metal component after preparation of the hard coating and promote the application of hard coating in the surface modification of metal components.

Description

Technical Field

[0001] The invention relates to a hard coating of a metal component and a preparation method thereof. Background Art

[0002] Key metal components in the fields of national defense and military aviation aircraft, ships, military combat tanks, nuclear power reactors, etc. often serve in harsh environments such as high temperature, high pressure, and high speed. They not only have to withstand severe interface friction, high-temperature oxidation, particle erosion damage and other pressures, but also undergo high-frequency vibration fatigue damage caused by complex environmental changes. Their actual service life is often short.

[0003] To extend the service life of these critical metal components, hard coatings are considered the most convenient and efficient surface strengthening measure for improving friction, corrosion, and high-temperature oxidation properties of major mechanical components due to their high hardness, stable physical and chemical properties, and minimal impact on the mechanical and physical and chemical properties of the substrate itself. However, under alternating loads, hard coatings with weak strain capacity can form rapid cracks that cleave metal components, or plastic metal components with slip steps on their surfaces that promote crack propagation toward the coating surface, ultimately reducing the fatigue life of the metal components. This is primarily due to a mismatch between the hard coating and the substrate in physical properties such as surface flatness and critical fracture stress.

[0004] To address these issues, recent research has focused on the structural design of hard coatings. For example, by introducing a soft coating of appropriate thickness within the hard coating or adjusting the thickness ratio of the hard coating to the soft coating, the low toughness of the hard coating can be improved, which can passivate tip cracks that propagate from metal components, thereby increasing the fatigue life of the metal components.

[0005] However, the mismatch between the multi-layer hard coating structure and the metal component substrate is still relatively large. In particular, when the plated parts are subjected to fatigue service in a high-temperature environment, the mismatch between the hard coating and the metal components in physical properties such as surface flatness and critical fracture stress will further increase, and the ability to inhibit fatigue crack initiation and propagation will be reduced. Therefore, a new method to improve the fatigue life of metal components after preparing hard coatings is urgently needed. Summary of the Invention

[0006] In order to eliminate the above-mentioned defects, the purpose of the present invention is to provide a method for improving the fatigue life of metal parts after preparing a hard coating and a metal part surface structure for improving the fatigue life of metal parts, so as to improve the fatigue life of metal parts after preparing a hard coating and promote the application of hard coating in the surface modification of metal parts.

[0007] To achieve the above-mentioned object, the present invention provides a method for improving the fatigue life of a metal component after preparing a hard coating, comprising the following steps: (1) before preparing the hard coating, applying a strengthening technology to strengthen the metal component substrate so that a compressive stress strengthening layer with a compressive stress state is formed on the surface of the metal component; (2) applying a coating preparation technology to prepare a hard coating on the surface of the strengthened metal component substrate.

[0008] As a preferred embodiment, the strengthening technology can be a single strengthening technology or a combination of two or more single strengthening methods.

[0009] As a preferred embodiment, the single strengthening technology is one of the following strengthening technologies: laser shock strengthening, shot peening, vibration finishing, and ion implantation / penetration.

[0010] As a preferred embodiment, in step (1), after the surface of the metal component is strengthened, the compressive stress gradually decreases from the surface to the inside, and the compressive stress strengthening layer is controlled within 3 mm.

[0011] As a preferred embodiment, the hardness of the hard coating is not lower than the hardness of the substrate.

[0012] As a preferred embodiment, the steps (1) and (2) are respectively as follows: the step (1): using N ion immersion injection / infiltration technology to perform surface strengthening on the TC6 blade, a. placing the TC6 blade on a rotating rack, starting the rotation axis and adjusting it to the rotation axis number 1, closing the vacuum chamber, and waiting for the vacuum degree to reach 1×10-3Pa, turning on the heating tube to 450°C; b. argon ion glow cleaning: temperature 450°C, argon working pressure 1Pa, bias 1000V, cleaning time 40min; c. strengthening process parameters: temperature 450°C, nitrogen pressure 7.5Pa, substrate power supply voltage -500V, injection / infiltration time 30min; the step (2): preparing a TiAlCN coating or a TiAlCrN coating on the surface of the blade strengthened by step (1); in addition, the method further comprises the step (3): after completing the preparation of the above-mentioned TiAlCN coating, when the vacuum chamber temperature drops to 80°C, gradually closing the molecular pump and the mechanical pump, opening the air inlet valve, and taking out the TC6 blade.

[0013] As a preferred embodiment, the step (2) is as follows: a. preparing a TiN layer: using metal Ti as a target, nitrogen as a working gas, and a DC power supply as an arc source, a 1 μm thick TiN coating is prepared on the surface of the reinforced TC6 blade, and the process conditions include: temperature 450°C, arc flow 150A, working gas pressure 1Pa, and bias voltage -100V; b. preparing a (Ti, Al) N layer: using two targets, a metal Ti target and a Ti3Al1 target, as targets, nitrogen as a working gas, and a DC power supply as an arc source, a 2.5 μm thick (Ti, Al) N layer is prepared on the TiN layer, and the process conditions include: temperature 450°C, arc flow 80A for the Ti target and arc flow 160A for the Ti1Al3 target, working gas pressure 1Pa, and bias voltage -100V; c. preparing a TiCN layer: using metal Ti as a target, nitrogen and acetylene as working gases, and a DC power supply as an arc source, a 3 μm thick TiCN layer is prepared on the (Ti, Al) N layer. The process conditions include: temperature 450°C, target arc current 160A, working gas pressure 0.8Pa, acetylene and nitrogen partial pressure ratio PC2H2:PN2 gradually increased from 0.07 to 0.2, and bias voltage -100V.

[0014] As a preferred embodiment, the step (2) is as follows: a. preparing a transition layer Cr layer: using metal Cr as a target, argon as a working gas, and a DC power supply as an arc source, a 100 nm thick Cr transition layer is prepared on the surface of the reinforced TC6 blade, and the process conditions include: temperature 450°C, air pressure 1Pa, and substrate bias voltage -100V; b. preparing a TiAlCrN layer process: using a metal Cr target and a Ti3Al1 target as targets, nitrogen as a working gas, and a DC power supply as an arc source, a 3.5 μm TiAlCrN layer is prepared on the transition layer Cr layer, and the process conditions include: temperature 450°C, Cr target arc flow 70A, Ti1Al3 target arc flow 160A, and substrate bias voltage -100V; c. preparing a TiAlCrN layer: using a metal Cr target and a Ti3Al1 target as targets, nitrogen as a working gas, and a DC power supply as an arc source, a 3 μm TiAlCrN layer is prepared on the TiAlCrN layer. The process conditions for the TiAlCrN layer include: temperature 450°C, Cr target arc current 70A, Ti1Al3 target arc current 160A, and substrate bias voltage -60V.

[0015] On the other hand, the present invention provides a metal component surface structure for improving the fatigue life of metal components, including: a compressive stress strengthening layer located on the surface of the metal component substrate formed by strengthening the metal component substrate using a strengthening technology, wherein the stress state of the compressive stress strengthening layer is compressive stress; and a hard coating formed on the surface of the compressive stress layer.

[0016] As a preferred embodiment, the metal component is a TC6 blade, the thickness of the compressive stress strengthening layer is within 3 mm, and the compressive stress of the compressive stress strengthening layer gradually decreases from the surface to the inside of the TC6 blade substrate; the hard coating is a TiAlCN coating or a TiAlCrN coating.

[0017] From the perspective of mechanical property matching, the present invention performs a strengthening treatment on the surface of the metal component before preparing the hard coating, introduces surface compressive stress, and improves its matching with the mechanical properties of the hard coating.

[0018] The present invention introduces compressive stress on the surface of the plastic metal component, thereby coordinating the deformation matching between the plastic metal component and the hard coating. This can not only reduce the probability of the hard coating forming rapid cracks that cleave the metal component, but also inhibit the initiation, expansion, and overflow of fatigue cracks on the surface and subsurface of the plastic metal component, thereby improving the fatigue life of the metal component. In particular, when the plated component is in fatigue service under high-temperature conditions, the plasma immersion injection / infiltration strengthening technology can significantly inhibit the release of compressive stress on the substrate surface, improve the mechanical matching between the substrate and the hard coating at high temperatures, and extend the high-temperature fatigue life of the metal component after the hard coating is prepared. The present invention has a simple process, strong industrial operability, and can easily achieve uniform strengthening and fatigue life improvement of mechanical heterogeneous components, making it easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings in the following description are only used to explain the concept of the present invention.

[0020] Figure 1 The process flow chart corresponding to the method of the present invention;

[0021] Figure 2 Schematic diagram of the structure of a metal component after hard coating is prepared according to the present invention. DETAILED DESCRIPTION

[0022] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0023] The embodiments described herein are specific embodiments of the present invention and are used to illustrate the concept of the present invention. They are illustrative and exemplary and should not be construed as limiting the embodiments of the present invention or the scope of the present invention. In addition to the embodiments described herein, those skilled in the art may also adopt other obvious technical solutions based on the claims and the disclosure of the specification, including technical solutions that adopt any obvious substitutions and modifications to the embodiments described herein.

[0024] The drawings in this specification are schematic diagrams, which assist in explaining the concept of the present invention and schematically show the shapes of various parts and their mutual relationships.

[0025] The present invention provides a method for improving the fatigue life of metal parts after preparing a hard coating, which serves the actual working conditions of mechanical parts. The specific method flow chart is as follows: Figure 1 As shown in FIG, it includes two parts: strengthening the surface of the metal component substrate and preparing the hard coating. After the two-part process of strengthening the substrate surface and preparing the hard coating, the schematic diagram of the metal component structure after preparing the hard coating is shown in FIG. Figure 2 After the hard coating is prepared, the metal component consists of a base material 1, a compressive stress strengthening layer 2 on the surface of the base, and a hard coating 3.

[0026] Specific process sequence, such as Figure 1 As shown, first, a single strengthening technology such as laser shock strengthening, shot peening, vibration finishing, ion implantation / dip-penetration, or a combination of two or more of the above strengthening technologies is applied to strengthen the surface of the metal component substrate 1, thereby forming a surface strengthening layer 2 on the surface 1; then, a hard coating 3 is prepared on the strengthening layer 2 using a hard coating preparation method.

[0027] The strengthening technology may be a single strengthening technology or a combination of two or more single strengthening methods. Single strengthening technologies include but are not limited to: laser shock peening, shot peening, vibration finishing, and ion implantation / infiltration.

[0028] See also Figure 2 After strengthening treatment, the surface of the metal part obtains a compressive stress strengthening layer 2. The compressive stress of the compressive stress strengthening layer 2 gradually decreases from the surface to the inside, and the compressive stress strengthening layer is controlled within 3mm.

[0029] The hardness of the hard coating layer 3 is preferably not lower than the hardness of the base material 1 .

[0030] The composite method for improving the fatigue life of a hard coating provided by the present invention will be described in detail below with reference to examples.

[0031] Example 1 This embodiment is a method for improving the fatigue life of a TC6 blade after preparing a TiAlCN hard coating, and the steps are as follows:

[0032] (1) The surface of TC6 blades was strengthened by N ion immersion injection / infiltration technology.

[0033] a. Place the TC6 blade on the rotating frame and turn the rotation axis to 1. Close the vacuum chamber and wait until the vacuum reaches 1×10-3Pa. Then turn on the heating tube to 450℃.

[0034] b. Argon ion glow cleaning: temperature 450°C, argon working pressure 1Pa, bias 1000V, cleaning time 40min;

[0035] c. Strengthening process parameters: temperature 450℃, nitrogen pressure 7.5Pa, substrate power supply voltage -500V, injection / infiltration time 30min.

[0036] (2) Preparation of TiAlCN coating on the blade surface strengthened by (1):

[0037] a. TiN Layer Preparation: Using metallic Ti as the target, nitrogen as the working gas, and a DC power supply as the arc source, a 1μm-thick TiN coating was deposited on the surface of a reinforced TC6 blade. Process conditions included: temperature 450°C, arc current 150A, working pressure 1Pa, and bias voltage -100V.

[0038] b. (Ti,Al)N Layer Preparation Process: Using two targets, a metallic Ti target and a Ti3Al1 target, nitrogen as the working gas, and a DC power supply as the arc source, a 2.5μm thick (Ti,Al)N layer was deposited on the TiN layer. Process conditions included a temperature of 450°C, an arc current of 80A for the Ti target and 160A for the Ti1Al3 target, a working gas pressure of 1Pa, and a bias voltage of -100V.

[0039] c. TiCN Layer Deposition Process: Using metallic Ti as the target, nitrogen and acetylene as the working gases, and a DC power supply as the arc source, a 3μm thick TiCN layer was deposited on the (Ti,Al)N layer. Process conditions included: temperature of 450°C, target arc current of 160A, working pressure of 0.8Pa, acetylene / nitrogen partial pressure ratio PC2H2:PN2 gradually increased from 0.07 to 0.2, and bias voltage of -100V.

[0040] (3) After the TiAlCN coating is prepared, when the vacuum chamber temperature drops to 80°C, the molecular pump and mechanical pump are gradually turned off, the air inlet valve is opened, and the TC6 blade is removed.

[0041] On a vibration fatigue test platform, a maximum stress value of σmax = 500 MPa was applied, and the fatigue life of the TC6 blade after obtaining the N ion implantation / infiltration strengthened composite TiAlCN coating was increased by 55% compared with the TC6 blade after preparing the TiAlCN coating without implantation / infiltration strengthening.

[0042] Example 2: This example is a method for improving the fatigue life of a TC6 blade after preparing a TiAlCrN hard coating. The steps are as follows:

[0043] The difference between this example and Example 1 lies in the preparation of the coating, i.e., step (2). The other steps are the same as those in Example 1. The detailed steps of step (2) are as follows:

[0044] (2) Preparation of TiAlCrN coating on blade surface:

[0045] a. Cr transition layer preparation process: Using metallic Cr as the target, argon as the working gas, and a DC power supply as the arc source, a 100nm thick Cr transition layer was deposited on the surface of a reinforced TC6 blade. Process conditions included: temperature 450°C, pressure 1 Pa, and substrate bias voltage -100V.

[0046] b. TiAlCrN Layer Preparation Process: Using two targets, a metallic Cr target and a Ti3Al1 target, nitrogen as the working gas, and a DC power supply as the arc source, a 3.5μm TiAlCrN layer was deposited on the transition Cr layer. Process conditions included a temperature of 450°C, an arc current of 70A for the Cr target, 160A for the Ti1Al3 target, and a substrate bias of -100V.

[0047] c. TiAlCrN Layer Preparation Process: Using two targets, a metallic Cr target and a Ti3Al1 target, nitrogen as the working gas, and a DC power supply as the arc source, a 3μm TiAlCrN layer was deposited on the TiAlCrN layer. Process conditions included a temperature of 450°C, an arc current of 70A for the Cr target, an arc current of 160A for the Ti1Al3 target, and a substrate bias of -60V.

[0048] On a vibration fatigue test platform, a maximum stress value of σmax = 500 MPa was applied, and the fatigue life of the TC6 blade after obtaining the N ion implantation / infiltration strengthened composite TiAlCrN coating was increased by 220% compared with the TC6 blade after preparing the TiAlCrN coating without N ion implantation / infiltration strengthening.

[0049] The above describes a method for improving the fatigue life of a metal component after preparing a hard coating and an embodiment of a metal component surface structure for improving the fatigue life of a metal component, the purpose of which is to explain the spirit of the present invention. The specific features of the present invention can be specifically designed according to the effects of the features disclosed above, and these designs are all achievable by those skilled in the art. Moreover, the various technical features disclosed above are not limited to the combination with other features disclosed. Those skilled in the art can also make other combinations between the various technical features according to the purpose of the present invention, so as to achieve the purpose of the present invention.

Claims

1. A method for improving the fatigue life of a metal part after preparing a hard coating, characterized in that: The following steps are involved: (1) Before preparing the hard coating, the metal component substrate is strengthened by applying a strengthening technology to form a compressive stress strengthening layer on the surface of the metal component with a compressive stress state. After the surface of the metal component is strengthened, the compressive stress gradually decreases from the surface to the inside, and the compressive stress strengthening layer is controlled within 3 mm; (2) Apply coating preparation technology to prepare hard coating on the surface of reinforced metal component substrate, Wherein, the steps (1) and (2) are respectively: Step (1): using N ion immersion injection / infiltration technology to strengthen the surface of TC6 blades, a. Place the TC6 blade on the rotating frame, turn on the rotation axis and adjust it to rotation axis 1, close the vacuum chamber, and wait until the vacuum degree reaches 1×10 -3 Pa, turn on the heating tube to 450℃; b. Argon ion glow cleaning: temperature 450°C, argon working pressure 1Pa, bias 1000V, cleaning time 40min; c. Strengthening process parameters: temperature 450°C, nitrogen pressure 7.5 Pa, substrate power supply voltage -500 V, injection / infiltration time 30 min; The step (2) is to prepare a TiAlCN coating or a TiAlCrN coating on the surface of the blade strengthened in the step (1); In addition, the method further comprises step (3): after the above-mentioned TiAlCN or TiAlCrN coating is prepared, when the vacuum chamber temperature drops to 80°C, the molecular pump and the mechanical pump are gradually turned off, the air inlet valve is opened, and the TC6 blade is taken out.

2. The method according to claim 1, characterized in that The hardness of the hard coating is not lower than the hardness of the substrate.

3. The method according to claim 1, characterized in that The step (2) is: a. TiN layer preparation: Using metallic Ti as the target, nitrogen as the working gas, and a DC power supply as the arc source, a 1μm-thick TiN coating was deposited on the surface of a reinforced TC6 blade. Process conditions included: temperature 450°C, arc current 150A, working pressure 1Pa, and bias voltage -100V. b. Preparation of (Ti,Al)N layer: Using a metallic Ti target and a Ti3Al1 target as targets, nitrogen as the working gas, and a DC power supply as the arc source, a 2.5μm thick (Ti,Al)N layer was deposited on the TiN layer. Process conditions included: temperature of 450°C, arc current of 80A for the Ti target and 160A for the Ti1Al3 target, working gas pressure of 1Pa, and bias voltage of -100V. c. TiCN Layer Preparation: Using metallic Ti as the target, nitrogen and acetylene as the working gases, and a DC power supply as the arc source, a 3μm thick TiCN layer was deposited on the (Ti,Al)N layer. Process conditions included a temperature of 450°C, a target arc current of 160A, an operating pressure of 0.8Pa, an acetylene / nitrogen partial pressure ratio (PC2H2:PN2) gradually increasing from 0.07 to 0.2, and a bias voltage of -100V.

4. The method according to claim 1, wherein The step (2) is: a. preparing a transition layer Cr layer: using metal Cr as a target, argon as a working gas, and a DC power supply as an arc source, a 100 nm thick Cr transition layer is prepared on the surface of the reinforced TC6 blade. The process conditions include: temperature 450°C, pressure 1Pa, and substrate bias voltage -100V; b. TiAlCrN layer preparation process: Using two targets, a metallic Cr target and a Ti3Al1 target, nitrogen as the working gas, and a DC power supply as the arc source, a 3.5μm TiAlCrN layer was deposited on the transition Cr layer. The process conditions included: temperature of 450°C, arc current of 70A for the Cr target, arc current of 160A for the Ti1Al3 target, and substrate bias of -100V. c. Preparation of TiAlCrN layer: Using two targets, a metal Cr target and a Ti3Al1 target, nitrogen as the working gas, and a DC power supply as the arc source, a 3μm TiAlCrN layer was prepared on the TiAlCrN layer. The process conditions include: temperature 450°C, arc current 70A for the Cr target, arc current 160A for the Ti1Al3 target, and substrate bias voltage -60V.

5. A metal component surface structure for improving the fatigue life of a metal component, comprising: A compressive stress strengthening layer is formed on the surface of a metal component substrate by strengthening the metal component substrate using a strengthening technology. The stress state of the compressive stress strengthening layer is compressive stress. The metal component is a TC6 blade. The compressive stress strengthening layer is a nitrogen ion immersion / infiltration layer. The thickness of the compressive stress strengthening layer is within 3 mm. In addition, the compressive stress of the compressive stress strengthening layer gradually decreases from the surface to the interior of the TC6 blade substrate. A hard coating is formed on the surface of the compressive stress layer, wherein the hard coating is a TiAlCN coating or a TiAlCrN coating.

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