Chromium-nickel-molybdenum gradient multilayer pvd coating resistant to hot-wet corrosion and method for producing same

Abstract

A chromium-nickel-molybdenum gradient multilayer PVD coating resistant to humid heat corrosion and its preparation method are disclosed, belonging to the field of metal surface protection technology. The coating is deposited on the surface of a metal substrate and comprises, from the inside out, a chromium transition layer, a chromium-nickel alloy intermediate layer, and a nickel-molybdenum alloy functional layer. The chromium transition layer has a thickness of 0.5 μm to 1.5 μm and a chromium content of not less than 95%. The chromium-nickel alloy intermediate layer has a thickness of 2.0 μm to 4.0 μm, in which the atomic percentage of nickel gradually increases from 5% to 10% near the chromium transition layer to 35% to 45% near the functional layer. The nickel-molybdenum alloy functional layer has a thickness of 1.0 μm to 3.0 μm, a molybdenum content of 15% to 25%, with the balance being nickel. The total coating thickness is 3.5 μm to 8.5 μm. The gradient intermediate layer alleviates thermal expansion mismatch stress, and the molybdenum element enhances the resistance to pitting corrosion in chlorine-containing humid heat environments. The multilayer structure extends the penetration path of corrosive media, making it suitable for long-term protection of metal components in marine equipment, aerospace, and energy equipment.

Description

Technical Field

[0001] This invention belongs to the field of metal surface protection technology, and relates to a chromium-nickel-molybdenum gradient multilayer PVD coating resistant to damp heat corrosion, its preparation method and application. Background Technology

[0002] Service environments such as marine atmosphere, salt spray, humid heat, and high temperature alternation can simultaneously cause problems such as surface oxidation, chloride ion pitting, thermal fatigue cracking of the film, and interface peeling. For key metal components in aerospace, marine equipment, energy equipment, and high-end manufacturing, the corrosion resistance of the base material itself is often insufficient to meet long-term service requirements. Therefore, it is usually necessary to prepare a protective coating on the surface of the metal substrate.

[0003] Existing chromium-based coatings, nickel-based coatings, and nickel-molybdenum or nickel-chromium-molybdenum alloy coatings all possess corrosion resistance or high-temperature resistance to a certain extent. Chromium contributes to the formation of a stable oxide film, nickel-based alloys provide a good foundation for corrosion resistance, and molybdenum can improve the stability of passivation films in chlorine-containing environments and enhance resistance to pitting corrosion. Physical vapor deposition (PVD) technology, with its advantages of low deposition temperature, dense film layers, controllable thickness, and suitability for preparing multilayer structures, has been widely used in the preparation of metal protective coatings.

[0004] However, traditional single-layer or simple double-layer coatings still have the following shortcomings: First, the difference in thermal expansion coefficient, elastic modulus, and crystal structure between the outer corrosion-resistant material and the metal substrate is significant, which can easily generate large interfacial stress under high-temperature cycling or alternating hot and cold conditions, leading to crack initiation, propagation, and even coating peeling. Second, although a single chromium layer has a certain degree of oxidation resistance, it may experience localized corrosion or defect penetration in high-humidity and chlorine-containing environments. Third, although direct deposition of nickel-molybdenum functional layers is beneficial to improving corrosion resistance, the film-substrate bonding and thermal stress buffering capacity are insufficient. Fourth, in existing multilayer corrosion-resistant coatings, abrupt changes in interlayer composition often lead to stress concentration, which is not conducive to stable service in long-term humid and high-temperature composite environments. Summary of the Invention

[0005] To address the deficiencies and shortcomings of existing technologies, the present invention aims to provide a chromium-nickel-molybdenum gradient multilayer PVD coating resistant to humid heat corrosion and its preparation method, thereby solving the problems of traditional single coatings or simple composite coatings being prone to film peeling, thermal fatigue cracking, chloride ion pitting, and rapid penetration of corrosive media along defects in humid heat, high temperature alternation, and salt spray environments.

[0006] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows:

[0007] A chromium-nickel-molybdenum gradient multilayer PVD coating resistant to humid heat corrosion is disclosed. The coating is deposited on the surface of a metal substrate and comprises, from the inside out, a chromium transition layer, a chromium-nickel alloy intermediate layer, and a nickel-molybdenum alloy functional layer. The chromium transition layer is directly deposited on the surface of the metal substrate and has a thickness of 0.5 μm to 1.5 μm. The chromium-nickel alloy intermediate layer is deposited on top of the chromium transition layer and has a thickness of 2.0 μm to 4.0 μm. The atomic percentage of nickel in the chromium-nickel alloy intermediate layer increases in the direction away from the metal substrate. The nickel-molybdenum alloy functional layer is deposited on top of the chromium-nickel alloy intermediate layer and has a thickness of 1.0 μm to 3.0 μm. The molybdenum content in the nickel-molybdenum alloy functional layer is 15% to 25%, with the balance being nickel and unavoidable impurities.

[0008] Preferably, the chromium transition layer is a pure chromium layer or a chromium-based substrate with chromium content not less than 95%.

[0009] Preferably, the atomic percentage of nickel in the chromium-nickel alloy interlayer gradually increases from 5% to 10% near the chromium transition layer to 35% to 45% near the nickel-molybdenum alloy functional layer.

[0010] Preferably, the chromium-nickel alloy interlayer is a linear continuous composition gradient layer, wherein the atomic percentage of nickel increases linearly and continuously in the direction away from the metal matrix.

[0011] Preferably, the chromium-nickel alloy intermediate layer consists of no less than 5 chromium-nickel sublayers, and the atomic percentage of nickel in each chromium-nickel sublayer increases sequentially in the direction away from the metal matrix, forming a step-like composition gradient.

[0012] Preferably, the metal matrix is ​​high-strength steel, stainless steel, nickel-based high-temperature alloy or titanium alloy.

[0013] Preferably, the total thickness of the coating is 3.5μm to 8.5μm, and a dense bonding interface is formed between the chromium transition layer, the chromium-nickel alloy intermediate layer and the nickel-molybdenum alloy functional layer.

[0014] A method for preparing a chromium-nickel-molybdenum gradient multilayer PVD coating resistant to humid heat corrosion, comprising the following steps: S1. Substrate pretreatment: The metal substrate is ground, polished and ultrasonically cleaned to remove surface oil and oxide scale, so that the surface roughness Ra of the metal substrate is no greater than 0.20μm. Then the metal substrate is placed in the physical vapor deposition vacuum chamber. S2. Ion etching: The physical vapor deposition vacuum chamber is evacuated to a vacuum level below 0.005 Pa, then argon gas is introduced, and a negative bias voltage of -50V to -150V is applied to the metal substrate for glow discharge cleaning for no less than 10 minutes. S3. Deposit of chromium transition layer: Using magnetron sputtering or arc ion plating technology, a chromium transition layer is deposited on the surface of a metal substrate using a chromium target as the target material. S4. Deposition of chromium-nickel alloy intermediate layer: Keep the chromium target current constant and increase the nickel target current. A chromium-nickel alloy intermediate layer is formed on the surface of the chromium transition layer by co-deposition of the chromium target and the nickel target. The atomic percentage of nickel in the chromium-nickel alloy intermediate layer increases in the direction away from the metal substrate. S5. Deposit a nickel-molybdenum alloy functional layer: Deposit a nickel-molybdenum alloy functional layer on the surface of a chromium-nickel alloy intermediate layer using a nickel-molybdenum alloy target, or by co-sputtering a nickel target and a molybdenum target. S6. Post-treatment: After deposition, the furnace is cooled to room temperature and then removed.

[0015] Preferably, in S4, the nickel target current is increased linearly or in stages.

[0016] Preferably, in steps S3 and S4, the temperature of the metal substrate is controlled between 200°C and 400°C during the deposition process, and the bias voltage of the metal substrate is controlled between -50V and -150V.

[0017] The above technical solution has the following beneficial effects: (1) The present invention provides a chromium-nickel-molybdenum gradient multilayer PVD coating resistant to humid heat corrosion and its preparation method. Through a specific hierarchical sequence of chromium transition layer, chromium-nickel alloy intermediate layer and nickel-molybdenum alloy functional layer, the three functions of film-substrate bonding, thermal stress buffering and resistance to chlorine-containing humid heat corrosion are respectively undertaken by different layers, and synergy is achieved through interlayer gradient transition.

[0018] (2) A chromium-nickel-molybdenum gradient multilayer PVD coating resistant to humid heat corrosion and its preparation method thereof, wherein the nickel content of the chromium-nickel alloy intermediate layer increases from the inside to the outside, avoiding abrupt interface between the chromium transition layer and the nickel-molybdenum alloy functional layer, which can reduce stress concentration caused by differences in thermal expansion coefficient and mechanical properties, and is beneficial to suppressing crack initiation and propagation under high temperature alternating conditions.

[0019] (3) A chromium-nickel-molybdenum gradient multilayer PVD coating resistant to humid heat corrosion and its preparation method thereof, wherein the molybdenum content in the nickel-molybdenum alloy functional layer is controlled at 15%-25%, which can utilize molybdenum element to improve the stability of passivation film in chlorine-containing corrosive media and enhance the anti-pitting corrosion ability in humid heat, salt spray and chlorine-containing environments.

[0020] (4) The present invention provides a chromium-nickel-molybdenum gradient multilayer PVD coating resistant to damp heat corrosion and its preparation method. The multilayer structure forms a barrier and extension effect on the penetration path of corrosive media. Even if there are minor defects on the surface, the chromium-nickel gradient intermediate layer and the chromium transition layer can still provide a barrier effect on the corrosive media, thereby improving the overall protection life.

[0021] (5) The present invention provides a chromium-nickel-molybdenum gradient multilayer PVD coating resistant to damp heat corrosion and its preparation method. It is prepared by PVD processes such as magnetron sputtering or arc ion plating. The deposition temperature is relatively low and the thickness is controllable, making it suitable for forming a micron-level dense protective coating on the surface of various metal substrates and complex parts. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the chromium-nickel-molybdenum gradient multilayer PVD coating of the present invention.

[0023] Figure 2 This is a schematic diagram showing the gradient of nickel content increasing along the thickness direction in the chromium-nickel alloy interlayer of the present invention.

[0024] The specific content of the present invention will be further explained in detail below with reference to comparative examples. Detailed Implementation

[0025] The present invention will be further described below with reference to embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Equivalent substitutions or conventional adjustments made by those skilled in the art to the deposition equipment, target type, process parameters, and substrate material without departing from the concept of the present invention should fall within the scope of protection of the present invention. Unless otherwise specified, "PVD" as used in the present invention includes magnetron sputtering, arc ion plating, and physical vapor deposition methods capable of multi-target co-deposition or composition gradient control.

[0026] Example 1 In this embodiment, a chromium-nickel-molybdenum gradient multilayer PVD coating is prepared on the surface of high-strength steel as the metal substrate.

[0027] First, the surface of the high-strength steel substrate is mechanically ground and polished to control the surface roughness Ra to no more than 0.20 μm. Then, it is ultrasonically cleaned with acetone, anhydrous ethanol and deionized water in sequence to remove oil, abrasive particles and surface oxide scale. After drying, it is placed in a physical vapor deposition vacuum chamber.

[0028] Next, the physical vapor deposition vacuum chamber is evacuated to a vacuum level below 0.005 Pa, and then argon gas is introduced to apply a negative bias voltage of -50V to -150V to the metal substrate for glow discharge cleaning for no less than 10 minutes to remove adsorbates on the substrate surface and activate the surface.

[0029] Then, using a pure chromium target (3N, purity ≥99.9%), a chromium transition layer was deposited on the substrate surface by magnetron sputtering, with the thickness of the chromium transition layer controlled at 0.8 μm. During the deposition process, the substrate temperature was controlled between 200℃ and 400℃, and the substrate bias voltage was controlled between -50V and -150V.

[0030] Subsequently, a chromium-nickel alloy interlayer was deposited using a co-sputtering method with chromium and nickel targets (both nickel and molybdenum targets were 3N5 with a purity ≥99.95%). During the deposition process, the chromium target current was kept constant while the nickel target current was increased linearly, so that the atomic percentage of nickel in the chromium-nickel alloy interlayer increased linearly and continuously from about 5% near the chromium transition layer to about 40% near the nickel-molybdenum alloy functional layer. The thickness of the chromium-nickel alloy interlayer was controlled to be 3.0 μm.

[0031] Finally, a nickel-molybdenum alloy functional layer is deposited using a nickel-molybdenum alloy target or a nickel and molybdenum target co-sputtering method, so that the molybdenum content in the functional layer is about 20% and the thickness is about 2.0 μm.

[0032] After deposition, the target source is turned off, and the furnace is cooled to room temperature before being removed, thus obtaining a chromium-nickel-molybdenum gradient multilayer PVD coating with a linear continuous compositional gradient intermediate layer.

[0033] Example 2 The difference between this embodiment and Embodiment 1 is that, after depositing a chromium transition layer on the substrate surface, a chromium-nickel alloy intermediate layer is prepared by adjusting the nickel target current in stages. The chromium-nickel alloy intermediate layer consists of five chromium-nickel sublayers, with the atomic percentage of nickel in each sublayer increasing sequentially away from the metal substrate: approximately 10% for the first sublayer, approximately 15% for the second, approximately 25% for the third, approximately 35% for the fourth, and approximately 40% for the fifth, forming a stepped composition gradient. This stepped composition gradient can achieve a thermal stress buffering effect similar to a continuous gradient while simplifying process control. The remaining steps and parameters are the same as in Embodiment 1.

[0034] Example 3 The difference between this embodiment and Embodiment 1 is that the metal substrate is a titanium alloy. The chromium transition layer improves the interfacial bonding between the coating and the titanium alloy surface. The remaining steps and parameters are the same as in Embodiment 1.

[0035] Example 4 The difference between this embodiment and Embodiment 1 is that the metal substrate is a nickel-based superalloy. The chromium-nickel alloy intermediate layer has good compositional compatibility with the substrate and the outer nickel-molybdenum functional layer, which helps to reduce interfacial mismatch during thermal cycling. The remaining steps and parameters are the same as in Embodiment 1.

[0036] This invention employs PVD technology to form a chromium-nickel-molybdenum gradient multilayer coating on a metal substrate. The process flow is clear, and the target materials and equipment are readily available. The coating thickness and composition gradient can be controlled by target current, target power, deposition time, and substrate bias voltage, making it suitable for mass production. This coating can be used in marine equipment, aerospace components, energy equipment, components operating in high-temperature and humid environments, and other metal parts that require simultaneous corrosion resistance, high-temperature oxidation resistance, and resistance to thermal fatigue spalling.

[0037] The above-described embodiments are merely preferred embodiments of the present invention and are not limited to the present invention. The chromium-nickel-molybdenum gradient multilayer PVD coating resistant to damp heat corrosion and its preparation method are not limited to the field of microwave absorption; the present invention can be used as a low infrared emissivity material for infrared stealth, a photocatalytic material, etc. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention that do not depart from the technical scope of the present invention, and applied to any field, constitute an infringement of the protection scope of the present invention and are included within the protection scope of the present invention.

Claims

1. A wet-heat corrosion resistant chromium-nickel-molybdenum gradient multilayer PVD coating, characterized in that, The coating is deposited on the surface of the metal substrate and includes, from the inside out, a chromium transition layer, a chromium-nickel alloy intermediate layer, and a nickel-molybdenum alloy functional layer. The chromium transition layer is directly deposited on the surface of the metal substrate and has a thickness of 0.5 μm to 1.5 μm. The chromium-nickel alloy interlayer is deposited on the chromium transition layer and has a thickness of 2.0 μm to 4.0 μm. The atomic percentage of nickel in the chromium-nickel alloy interlayer increases in the direction away from the metal substrate. The nickel-molybdenum alloy functional layer is deposited on the chromium-nickel alloy intermediate layer, with a thickness of 1.0 μm to 3.0 μm. The molybdenum content in the nickel-molybdenum alloy functional layer is 15% to 25%, with the balance being nickel and unavoidable impurities.

2. The Cr-Ni-Mo gradient multilayer PVD coating according to claim 1, characterized in that The chromium transition layer is a pure chromium layer or a chromium-based substrate with a chromium content of not less than 95%.

3. The Cr-Ni-Mo gradient multilayer PVD coating according to claim 1, characterized in that, The atomic percentage of nickel in the chromium-nickel alloy intermediate layer gradually increases from 5% to 10% near the chromium transition layer to 35% to 45% near the nickel-molybdenum alloy functional layer.

4. The Cr-Ni-Mo gradient multilayer PVD coating according to claim 3, characterized in that The chromium-nickel alloy intermediate layer is a linear continuous composition gradient layer, wherein the atomic percentage of nickel increases linearly and continuously in the direction away from the metal matrix.

5. The Cr-Ni-Mo gradient multilayer PVD coating according to claim 3, characterized in that The chromium-nickel alloy intermediate layer consists of no less than 5 chromium-nickel sublayers, and the atomic percentage of nickel in each chromium-nickel sublayer increases sequentially in the direction away from the metal matrix, forming a step-like composition gradient.

6. The Cr-Ni-Mo gradient multilayer PVD coating according to claim 1, characterized in that, The metal matrix is ​​high-strength steel, stainless steel, nickel-based high-temperature alloy, or titanium alloy.

7. The Cr-Ni-Mo gradient multilayer PVD coating according to any of claims 1 to 6, characterized in that The total thickness of the coating is 3.5μm to 8.5μm, and a dense bonding interface is formed between the chromium transition layer, the chromium-nickel alloy intermediate layer and the nickel-molybdenum alloy functional layer.

8. A method for preparing a chromium-nickel-molybdenum gradient multilayer PVD coating resistant to humid heat corrosion as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Substrate pretreatment: The metal substrate is ground, polished and ultrasonically cleaned to remove surface oil and oxide scale, so that the surface roughness Ra of the metal substrate is not greater than 0.20μm. Then the metal substrate is placed in the physical vapor deposition vacuum chamber. S2. Ion etching: The physical vapor deposition vacuum chamber is evacuated to a vacuum level below 0.005 Pa, then argon gas is introduced, and a negative bias voltage of -50V to -150V is applied to the metal substrate for glow discharge cleaning for no less than 10 minutes. S3. Deposit of chromium transition layer: Using magnetron sputtering or arc ion plating technology, a chromium transition layer is deposited on the surface of the metal substrate using a chromium target as the target material. S4. Deposit a chromium-nickel alloy intermediate layer: Keep the chromium target current constant and increase the nickel target current to form a chromium-nickel alloy intermediate layer on the surface of the chromium transition layer by co-depositing the chromium target and the nickel target. The atomic percentage of nickel in the chromium-nickel alloy intermediate layer increases in the direction away from the metal substrate. S5. Deposit a nickel-molybdenum alloy functional layer: Deposit a nickel-molybdenum alloy functional layer on the surface of the chromium-nickel alloy intermediate layer using a nickel-molybdenum alloy target, or by co-sputtering a nickel target and a molybdenum target. S6. Post-treatment: After deposition, the furnace is cooled to room temperature and then removed.

9. The preparation method according to claim 8, characterized in that, In step S4, the nickel target current is increased either linearly or in stages.

10. The preparation method according to claim 8, characterized in that, In steps S3 and S4, the temperature of the metal substrate is controlled between 200°C and 400°C during the deposition process, and the bias voltage of the metal substrate is controlled between -50V and -150V.

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