A high bond force composite coating for hydraulic valve stem surfaces and method of making same
Patent Information
- Application Number
- CN202611174948.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-04
- Publication Date
- 2026-09-25
AI Technical Summary
[0004]本发明针对现有液压阀杆表面涂层结合力不足的技术问题，提供一种用于液压阀杆表面的高结合力复合涂层及其制备方法
通过Cr(N)间隙固溶体与钢基体的BCC晶格匹配消除界面失配应力，通过Fe-Si金属间化合物纳米钉扎相实现化学键合，通过非晶Si晶界包裹层吸收和钝化应力，三重机制协同作用使涂层结合力显著提升。CrAlNSi复合层中非晶外壳包裹CrAlN纳米晶的核-壳结构，通过裂纹偏转和界面解耦机制有效吸收冲击能量，防止裂纹贯穿扩展，显著提升涂层的抗冲击疲劳寿命。
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Figure CN122811700A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of hydraulic valve stem surface coating technology, and in particular to a high-adhesion composite coating for hydraulic valve stem surfaces and its preparation method. Background Technology
[0002] Preparing a hard protective coating on the surface of a hydraulic valve stem is an effective way to extend its service life. Currently, various coating schemes for hydraulic valve stem surfaces have been disclosed in the prior art. For example, some existing technologies employ a multi-layer composite coating structure consisting of a gradient transition layer, a composite functional layer, and an amorphous carbon top layer, wherein the gradient transition layer is composed of a metal layer, a metal carbide layer, or a metal nitride layer.
[0003] However, the aforementioned existing technologies still have significant shortcomings in terms of the adhesion between the coating and the substrate, mainly in the following aspects: First, poor interface matching leads to lattice mismatch stress. Hydraulic valve stems commonly use body-centered cubic (BCC) substrate materials (such as 40Cr and 42CrMo alloy steel), while traditional hard coatings (such as CrN and TiN) have a face-centered cubic (FCC) structure. A significant difference in lattice constants between the two results in a large number of mismatched dislocations and lattice distortions at the interface. These microscopic defects are highly susceptible to becoming crack initiations under stress, leading to coating peeling. Second, the interlayer interface is abruptly different, resulting in stress concentration. In existing technologies, there is often a clear abrupt change in composition between the transition layer and the functional layer. The difference in thermal expansion coefficients generates significant residual thermal stress during coating cooling, weakening the interlayer bonding strength. Summary of the Invention
[0004] This invention addresses the technical problem of insufficient adhesion of existing coatings on the surface of hydraulic valve stems by providing a high-adhesion composite coating for the surface of hydraulic valve stems and its preparation method. This invention achieves high-strength bonding between the coating and the substrate through a dual-layer synergistic design of "interfacial reaction anchoring + nanocomposite reinforcement," while simultaneously ensuring impact resistance, wear resistance, and lubrication performance.
[0005] The Cr(N) interstitial solid solution maintains a BCC structure with a lattice mismatch of less than 1.5% with the steel substrate (BCC structure), far lower than the greater than 20% mismatch between traditional FCC structure coatings (such as TiN) and the steel substrate. This allows coating atoms to grow directly epitaxially on the substrate lattice, eliminating the weak link at the atomic scale.
[0006] Highly reactive free Si atoms are forcibly injected into the surface layer of a steel substrate (to a depth of 10-20 nm). The injected reactive Si atoms undergo a solid-state diffusion reaction with Fe atoms in the substrate to generate FeSi and / or Intermetallic compound nanoparticles (2-5 nm in diameter) are distributed in an island-like discrete form at the matrix interface. These Fe-Si compounds form strong chemical bonds that combine covalent and metallic bonds, with a binding strength far exceeding that of physical adsorption.
[0007] CrAlN nanocrystals embedded in amorphous materials in the CrAlNSi composite layer A core-shell structure is formed in the matrix.
[0008] When CrAlN grains are refined to 5-15 nm, there is almost no space within the grain to accommodate dislocation multiplication. External loads cannot be released through dislocation slip; only extremely large external forces can further indentation, resulting in extremely high shear strength. (Amorphous) The outer shell physically isolates adjacent grains from direct contact, preventing grain aggregation, growth, and recrystallization, thus maintaining the structural stability of the coating at high temperatures. When microcracks propagate to the interface between the grains and the amorphous outer shell, the residual compressive stress at the interface forces the cracks to deflect, dissipating energy along the grain boundaries and preventing the cracks from penetrating the entire coating, greatly enhancing its resistance to impact spalling.
[0009] Preferably, the thickness of the CrSiN composite layer is 150-350 nm, the thickness of the CrAlNSi composite layer is 2.5-4.0 μm, and the total thickness of the composite coating is controlled between 2.7-4.4 μm.
[0010] Preferably, the grain size of the Cr(N) interstitial solid solution is 5-15 nm, and the amorphous Si is wrapped in an amorphous film with a thickness of 1-3 nm at the grain boundaries of the Cr(N) interstitial solid solution.
[0011] Preferably, the grain size of the CrAlN nanocrystals is 5-15 nm.
[0012] Preferably, an Fe-Si intermetallic compound nano-pinned phase is formed at the interface between the CrSiN composite layer and the hydraulic valve stem substrate, wherein the Fe-Si intermetallic compound nano-pinned phase is FeSi and / or Its particle size is 2-5 nm, and it is distributed in an island-like discrete manner at a depth of 2-10 nm at the interface of the hydraulic valve stem matrix.
[0013] Preferably, in the CrAlNSi composite layer, the atomic ratio of Cr to Al is (1.2-2.0):1; the amorphous... The matrix is wrapped around the CrAlN nanocrystals in the form of a shell with a thickness of 1-3 nm, forming a core-shell structure.
[0014] The present invention also provides a method for preparing the above-mentioned composite coating, comprising the following steps: S1: Perform ion etching cleaning on the hydraulic valve stem substrate; S2: The CrSiN composite layer is deposited on the surface of the substrate using magnetron sputtering technology; S3: The CrAlNSi composite layer is deposited on the surface of the CrSiN composite layer using magnetron sputtering technology.
[0015] Preferably, in step S2, co-sputtering is performed using a Cr target and a Si target to deposit the CrSiN composite layer; the sputtering power of the Cr target is 612 kW, and the sputtering power of the Si target is 1.0-2.5 kW. The flow rate was 2-5 sccm, the deposition temperature was 300-400℃, and the deposition time was 5-10 min. During the magnetron sputtering deposition process... The flow rate was strictly controlled at an extremely low level of 2-5 sccm, at which point the target sputtering was in the transition mode region. Under these conditions, the number of N atoms deposited on the substrate surface was far lower than the number of Cr atoms (the Cr:N ratio was approximately 1:0.2-0.3), failing to meet the nitrogen content required for the CrN stoichiometric ratio (Cr:N=1:1). N atoms could not form stoichiometric CrN compounds with Cr, but instead existed as interstitial solid solutions in the body-centered cubic (BCC) lattice of Cr, forming Cr(N) interstitial solid solutions. Simultaneously, because Si has a much stronger affinity for N than Cr, in this extremely nitrogen-depleted environment, the limited number of N atoms were preferentially competed for by Si. However, due to the severe deficiency of total N, most of the Si could not obtain sufficient N to form N atoms. Instead, it exists as amorphous free silicon (a-Si), which is uniformly dispersed and wrapped around the boundaries of Cr(N) grains to form an amorphous film.
[0016] Preferably, in step S3, co-sputtering is performed using a CrAl alloy target and a Si target to deposit the CrAlNSi composite layer; the sputtering power of the CrAl alloy target is 6-12 kW, and the sputtering power of the Si target is 0.5-2.0 kW. Under the condition of uninterrupted plasma glow discharge, the deposition is carried out within 0.5-2 min. The flow rate was linearly increased from 2-5 sccm to 30-40 sccm, and the peak voltage of the pulsed negative bias was linearly reduced from -200V to -300V to -50V to -100V. Deposition temperature: 350-450℃ (preferably 400℃), deposition time: 90-150 min (preferably 120 min).
[0017] During magnetron sputtering deposition, Cr, Al, Si, and N atoms arrive at the substrate surface almost simultaneously. Because Si has a much stronger affinity for N than Cr / N and Al / N, Si atoms preferentially bind to N. However, under the non-equilibrium conditions of rapid PVD condensation, Unable to crystallize in time, it was forced to freeze into an amorphous state. Meanwhile, Cr and Al combine with the remaining N to form CrAlN solid solution nanocrystals. Since both CrN and AlN have NaCl-type face-centered cubic structures and similar lattice constants, they readily dissolve to form a single-phase solid solution. To reduce the total energy of the system, They automatically segregate and coat the surface of CrAlN nanocrystals, forming an amorphous shell.
[0018] Preferably, the process parameters for the ion etching cleaning process in step S1 are as follows: Ion etching, bias voltage -800 to -1000V, etching time 20~30 min.
[0019] Preferably, between steps S1 and S2, a further step S1-1 is included, which involves pre-treating the surface of the hydraulic valve stem substrate with metal ion implantation. This pre-treatment uses at least one metal ion selected from Ti, Cr, Mo, W, or V to implant the surface of the hydraulic valve stem substrate. The implantation energy is 20-60 keV, and the implantation dose is... .
[0020] High-energy metal ions penetrate the substrate surface, forming a substrate-metal hybrid layer with a depth of 20-80 nm. This eliminates the clear interface between the coating and the substrate, extending the bonding force from a two-dimensional interface to a three-dimensional gradient transition region. The implanted metal ions (such as Ti and Cr) can form M-Fe-Si (M = Ti, Cr, etc.) ternary intermetallic compounds with the Fe-Si pinned phase, which are interspersed with the Fe-Si binary pinned phase to form a denser composite pinned interface layer.
[0021] The present invention has the following beneficial effects: The coating's adhesion is significantly enhanced through a three-pronged mechanism: 1) eliminating interfacial mismatch stress by matching the Cr(N) interstitial solid solution with the BCC lattice of the steel substrate; 2) achieving chemical bonding through Fe-Si intermetallic compound nano-pinning phases; and 3) absorbing and passivating stress through an amorphous Si grain boundary encapsulation layer. The amorphous Si in the CrAlNSi composite layer... The core-shell structure encapsulating CrAlN nanocrystals effectively absorbs impact energy through crack deflection and interface decoupling mechanisms, preventing crack penetration and propagation, and significantly improving the impact fatigue life of the coating.
[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0023] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic flowchart illustrating a method for preparing a high-adhesion composite coating for the surface of a hydraulic valve stem, as proposed in this invention. Detailed Implementation
[0024] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.
[0025] A high-adhesion composite coating for the surface of a hydraulic valve stem, the high-adhesion composite coating being composed of a CrSiN composite layer and a CrAlNSi composite layer stacked sequentially from bottom to top on the surface of the hydraulic valve stem substrate. The CrSiN composite layer comprises Cr(N) interstitial solid solution and amorphous Si distributed freely at the grain boundaries of the Cr(N) interstitial solid solution. The CrSiN composite layer, by atomic percentage, contains 75%-82% Cr, 6%-10% Si, and 10%-16% N. The CrAlNSi composite layer comprises amorphous... The matrix, and the inlay in the amorphous The CrAlN nanocrystals in the matrix, wherein the CrAlNSi composite layer contains, by atomic percentage, 20%-30% Cr, 12%-20% Al, 40%-55% N, and 5%-12% Si.
[0026] like Figure 1 As shown, the present invention also provides a method for preparing the above-mentioned composite coating, comprising the following steps: S1: Perform ion etching cleaning on the hydraulic valve stem substrate; S2: The CrSiN composite layer is deposited on the surface of the substrate using magnetron sputtering technology; S3: The CrAlNSi composite layer is deposited on the surface of the CrSiN composite layer using magnetron sputtering technology.
[0027] The present invention will be further described below with reference to embodiments.
[0028] In the following embodiments, the hydraulic valve stem base material is 40Cr alloy steel.
[0029] Example 1
[0030] This embodiment provides a high-adhesion composite coating for the surface of a hydraulic valve stem and its preparation method.
[0031] The composite coating consists of a CrSiN composite layer and a CrAlNSi composite layer stacked sequentially from bottom to top on the surface of the hydraulic valve stem substrate.
[0032] The CrSiN composite layer has a thickness of 220 nm and, by atomic percentage, contains 78% Cr, 8% Si, and 14% N. Its microstructure consists of interstitial N atoms dissolved in the body-centered cubic lattice of Cr to form a Cr(N) interstitial solid solution (grain size approximately 10 nm), with amorphous Si encapsulating the Cr(N) grain boundaries as an amorphous film approximately 2 nm thick. FeSi and [other compounds] are formed at the interface between the CrSiN composite layer and the substrate. The nano-pinned phase (with a particle size of about 3 nm) is distributed in an island-like discrete manner at a depth of about 5 nm at the matrix interface.
[0033] The CrAlNSi composite layer has a thickness of 3.2 μm and, by atomic percentage, contains 25% Cr, 16% Al, 48% N, and 11% Si, with an atomic ratio of 1.56:1 for Cr to Al. Its microstructure consists of CrAlN nanocrystals (grain size approximately 10 nm) embedded in an amorphous substrate. In the matrix, amorphous A core-shell structure is formed by enclosing CrAlN nanocrystals with a shell of about 2 nm thickness.
[0034] The total thickness of the composite coating is approximately 3.42 μm.
[0035] 3. Preparation method Includes the following steps: S1: Perform ion etching cleaning on the hydraulic valve stem substrate. Place the substrate into the vacuum chamber of a magnetron sputtering coating machine and evacuate to a background vacuum level ≤5×10⁻⁶. -4 Pa, Ar gas is introduced, and a bias voltage of -900V is applied to perform... Ion etching for 25 minutes removes oil and natural oxide layer from the substrate surface.
[0036] S1-1 (Optional): After step S1 and before step S2, a metal vapor vacuum arc (MEVVA) ion source is used to perform ion implantation pretreatment on the substrate surface with Ti ions. The implantation energy is 40 keV and the implantation dose is [not specified]. .
[0037] S2: A CrSiN composite layer was deposited on the substrate surface using magnetron sputtering. Co-sputtering was performed using a Cr target (purity ≥99.9%) and a Si target (purity ≥99.999%), with a sputtering power of 8 kW for the Cr target and 1.5 kW for the Si target. gas (flow rate 80 sccm) and The gas is controlled by a closed-loop feedback control system for plasma emission spectroscopy (OEM). The flow rate was precisely locked at 3.5 ± 0.3 sccm to stabilize the target sputtering in the transition mode region. A pulsed negative bias was applied with a peak voltage of -250V, a frequency of 150 kHz, and a duty cycle of 20%. The deposition temperature was 350℃, and the deposition time was 6 min to deposit a CrSiN composite layer on the substrate surface.
[0038] S3: A CrAlNSi composite layer was deposited on the surface of the CrSiN composite layer using magnetron sputtering. Under the condition of uninterrupted plasma glow discharge, the deposition was completed within 1 minute. The flow rate was linearly increased from 3.5 sccm to 35 sccm, and the peak voltage of the pulsed negative bias was linearly reduced from -250V to -75V. Co-sputtering was performed using a CrAl alloy target (Cr:Al atomic ratio = 60:40) and a Si target, with a sputtering power of 8 kW for the CrAl alloy target and 1.0 kW for the Si target. The deposition temperature was 400℃ and the deposition time was 120 min, depositing a CrAlNSi composite layer on the surface of the CrSiN composite layer.
[0039] After deposition, the sample is slowly cooled to below 200°C in a vacuum environment and then removed.
[0040] Performance testing: (1) Adhesion test: The coating adhesion was tested by scratch method (Rockwell C indenter, loading rate 100 N / min), and the critical load Lc2 was 95 N.
[0041] (2) Hardness test: The hardness was 37.2 GPa, which was tested using a nanoindenter.
[0042] (3) Friction coefficient test: A ball-disc friction and wear tester (for grinding) was used. The ball has a load of 5 N, a linear velocity of 0.1 m / s, and a friction coefficient of 0.33.
[0043] Example 2
[0044] The difference between this embodiment and Embodiment 1 is as follows: the CrSiN composite layer has a Cr content of 75%, a Si content of 10%, and a N content of 15% (atomic percentage), with a thickness of 150 nm; the CrAlNSi composite layer has a Cr content of 20%, an Al content of 20%, a N content of 48%, and a Si content of 12% (atomic percentage), with a thickness of 2.5 μm. In the preparation method, the deposition time for step S2 is 5 min, and the deposition time for step S3 is 90 min. The rest is the same as in Embodiment 1.
[0045] Tests showed that the critical load for bonding force Lc2 was 82 N, the hardness was 35.8 GPa, and the coefficient of friction was 0.35.
[0046] Example 3
[0047] The difference between this embodiment and Embodiment 1 is as follows: the CrSiN composite layer has a Cr content of 82%, a Si content of 6%, and a N content of 12% (atomic percentage), with a thickness of 350 nm; the CrAlNSi composite layer has a Cr content of 30%, an Al content of 12%, a N content of 42%, and a Si content of 6% (atomic percentage), with a thickness of 4.0 μm. In the preparation method, the deposition time for step S2 is 10 min, and the deposition time for step S3 is 150 min. The rest is the same as in Embodiment 1.
[0048] Tests showed that the critical load for bonding force Lc2 was 88 N, the hardness was 36.5 GPa, and the coefficient of friction was 0.34.
[0049] Example 4
[0050] The difference between this embodiment and Embodiment 1 is that a metal ion implantation pretreatment step S1-1 is added between steps S1 and S2, in which Cr ions are used to implant ions into the substrate surface at an implantation energy of 50 keV and an implantation dose of [missing information]. The rest is the same as in Example 1.
[0051] Testing showed that the critical load Lc2 for bonding force increased to 125 N, an increase of approximately 32% compared to Example 1. The hardness was 37.5 GPa, and the coefficient of friction was 0.32.
[0052] Example 5
[0053] The difference between this embodiment and Embodiment 1 is that Ti ions are used in the metal ion implantation pretreatment step S1-1, the implantation energy is 30 keV, and the implantation dose is... The rest is the same as in Example 1.
[0054] The test results showed that the critical load Lc2 of the bonding force was 118 N, the hardness was 37.0 GPa, and the coefficient of friction was 0.33.
[0055] Comparative Example 1 The difference between this comparative example and Example 1 is that no CrSiN composite layer is deposited; instead, a CrAlNSi composite layer (3.2 μm thick, composition the same as in Example 1) is deposited directly on the substrate surface. Step S2 is omitted in the preparation method, and step S3 involves direct deposition on the substrate surface. The rest is the same as in Example 1.
[0056] Tests showed that the critical load for bonding strength, Lc2, was only 35 N, the hardness was 36.8 GPa, and the coefficient of friction was 0.34. This indicates that the "reaction anchoring" effect of the CrSiN composite layer plays a decisive role in improving the bonding strength.
[0057] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.
Claims
1. A high-adhesion composite coating for the surface of a hydraulic valve stem, characterized in that, The high-adhesion composite coating consists of a CrSiN composite layer and a CrAlNSi composite layer stacked sequentially from bottom to top on the surface of the hydraulic valve stem substrate. The CrSiN composite layer includes Cr(N) interstitial solid solution and non-static Si distributed freely at the grain boundaries of the Cr(N) interstitial solid solution. The CrSiN composite layer contains 75%-82% Cr, 6%-10% Si, and 10%-16% N by atomic percentage. The CrAlNSi composite layer includes amorphous... The matrix, and the inlay in the amorphous The CrAlN nanocrystals in the matrix, wherein the CrAlNSi composite layer contains, by atomic percentage, 20%-30% Cr, 12%-20% Al, 40%-55% N, and 5%-12% Si.
2. The high-adhesion composite coating for the surface of a hydraulic valve stem according to claim 1, characterized in that, The thickness of the CrSiN composite layer is 150-350 nm, the thickness of the CrAlNSi composite layer is 2.5-4.0 μm, and the total thickness of the composite coating is controlled between 2.7-4.4 μm.
3. The high-adhesion composite coating for the surface of a hydraulic valve stem according to claim 1, characterized in that, The grain size of the Cr(N) solid solution is 5-15 nm, and the amorphous Si is wrapped in an amorphous film with a thickness of 1-3 nm at the grain boundaries of the Cr(N) solid solution.
4. The high-adhesion composite coating for the surface of a hydraulic valve stem according to claim 1, characterized in that, The grain size of the CrAlN nanocrystals is 5-15 nm.
5. The high-adhesion composite coating for the surface of a hydraulic valve stem according to claim 1, characterized in that, Fe-Si intermetallic compound nano-pinning phases are formed at the interface between the CrSiN composite layer and the hydraulic valve stem substrate. These Fe-Si intermetallic compound nano-pinning phases are FeSi and / or Its particle size is 2-5 nm, and it is distributed in an island-like discrete manner at a depth of 2-10 nm at the interface of the hydraulic valve stem matrix.
6. A method for preparing a high-adhesion composite coating for the surface of a hydraulic valve stem as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Perform ion etching cleaning on the hydraulic valve stem substrate. S2. The CrSiN composite layer is deposited on the surface of the substrate using magnetron sputtering technology; S3. The CrAlNSi composite layer is deposited on the surface of the CrSiN composite layer using magnetron sputtering technology.
7. The preparation method according to claim 6, characterized in that, In step S2, the CrSiN composite layer is deposited by co-sputtering using a Cr target and a Si target; the sputtering power of the Cr target is 6-12 kW, and the sputtering power of the Si target is 1.0-2.5 kW. The flow rate was 2-5 sccm, the deposition temperature was 300-400℃, and the deposition time was 5-10 min. According to the preparation method of claim 6, the CrAl alloy target and the Si target are used as targets for co-sputtering to deposit the CrAlNSi composite layer; the sputtering power of the CrAl alloy target is 6-12 kW, and the sputtering power of the Si target is 0.5-2.0 kW. Under the condition of maintaining uninterrupted plasma glow discharge, the deposition is carried out within 0.5-2 min. The flow rate is linearly increased from 2-5 sccm to 30-40 sccm, and the peak voltage of the pulse negative bias is linearly reduced from -200V to -300V to -50V to -100V.
8. The preparation method according to claim 6, characterized in that, In step S1, the process parameters for the ion etching cleaning process are: Ar + Ion etching, bias voltage -800 to -1000V, etching time 20-30 min.
9. The preparation method according to claim 6, characterized in that, Between steps S1 and S2, a further step S1-1 is included: pre-treatment of the hydraulic valve stem substrate surface by metal ion implantation. At least one metal ion selected from Ti, Cr, Mo, W, or V is used to implant the hydraulic valve stem substrate surface with an implantation energy of 20-60 keV and an implantation dose of [missing information]. ).