Brake disc with gradient wear-resistant ceramic composite coating

Abstract

The invention discloses a brake disc with a gradient wear-resistant ceramic composite coating, and belongs to the technical field of automobile brake systems. The brake disc comprises a brake disc base body, and three layers of gradient composite coatings with different functions are sequentially prepared on the friction surface of the brake disc base body through a laser cladding technology and are respectively a combination transition layer, a hard supporting layer and a functional ceramic layer from inside to outside. The bonding transition layer is made of Fe-based or Ni-based alloy, metallurgical bonding with a matrix is achieved, and thermal stress is relieved; the hard supporting layer uses Co-based or Ni-based high-temperature alloy as a binding phase, hard ceramic particles such as WC and SiC are distributed in a dispersed mode, and rigid supporting and heat conduction are provided. The functional ceramic layer is compounded with Al2O3, ZrO2, SiC and a solid lubricant, and has the characteristics of high hardness, high-temperature stability and antifriction. The problems that a traditional brake disc is poor in abrasion resistance and prone to heat fading, and a coating is prone to stripping are effectively solved, the braking performance is remarkably improved, and the service life is remarkably prolonged.

Description

Technical Field

[0001] This invention belongs to the field of automotive braking system technology, specifically relating to a brake disc with a special gradient wear-resistant coating prepared by laser cladding technology. Background Technology

[0002] Brake discs are the core component of a car's braking system, and their performance directly affects driving safety. Currently, most brake discs are made of gray cast iron, which, while advantageous in terms of cost and manufacturing process, suffers from poor wear resistance, susceptibility to rust, and thermal fade at high temperatures, such as a decrease in the coefficient of friction. To improve performance, existing technologies include spraying wear-resistant coatings onto the brake disc surface or performing heat treatment. However, these methods result in coatings with weak adhesion to the substrate, making them prone to peeling, and the coating properties are limited, failing to meet the requirements of complex operating conditions.

[0003] Laser cladding technology, as an advanced surface modification technique, can produce dense coatings that are metallurgically bonded to the substrate. However, designing the composition and structure of the coating to ensure good bonding with the cast iron substrate, excellent wear resistance, friction reduction, and thermal shock resistance, while also achieving good compatibility with the mating component, brake pads, remains a pressing problem to be solved. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a multi-layer gradient ceramic composite coating brake disc with a reasonable structural design, clearly defined functions of each layer, and significant synergistic effects. This brake disc exhibits extremely high wear resistance, a stable coefficient of friction, and excellent high-temperature performance.

[0005] This invention includes the following technical solutions: A brake disc with a gradient wear-resistant ceramic composite coating includes a brake disc substrate. Its innovation lies in the sequential cladding of three functionally different ceramic composite coating layers onto the friction surface of the brake disc substrate using laser cladding technology, forming a gradient composite structure. These three coating layers, from the inside out, are: a bonding transition layer, a hard support layer, and a functional ceramic layer.

[0006] Preferably, the innermost layer is a bonding transition layer, which is made of Fe-based or Ni-based alloy that matches the thermal expansion coefficient of the cast iron matrix. By optimizing alloying elements (such as B and Si) to lower the melting point and improve wettability, a strong metallurgical bond with the matrix is ​​ensured, and internal stress caused by thermal expansion differences is alleviated.

[0007] Preferably, the intermediate hard support layer uses Co-based or Ni-based high-temperature alloys as the binder phase and disperses high volume fraction of hard carbide ceramic particles (such as WC, SiC) to form the rigid skeleton of the coating, which mainly undertakes the functions of resisting plastic deformation, resisting abrasive wear and supporting the outer layer.

[0008] Preferably, the outermost layer is a functional ceramic layer, with Co-based or Ni-based cermet as the matrix, and a composite of high volume fraction oxide ceramics (such as Al2O3, ZrO2) and solid lubricant. This layer directly participates in friction and has high hardness, excellent high temperature stability, stable friction coefficient and certain self-lubricating and friction-reducing properties. It is the core functional layer that ensures the long-term wear resistance and heat fade resistance of the brake disc.

[0009] Optionally, a transition layer may be incorporated, the composition of which, by weight percentage, is: Fe balance, Cr 15-20%, Ni 8-12%, B 3.0-4.5%, Si 3.5-4.5%, C 0.6-1.0%, with a layer thickness controlled at 0.15-0.25 mm. This layer achieves excellent self-fluxing and wettability through its rich B and Si elements. Its core function is to form a strong metallurgical bond with the cast iron matrix and to alleviate thermal stress.

[0010] Optionally, a hard support layer is provided, with the metal binder phase consisting of the remainder Co, 28-32% Cr, 4-5% W, and 1.0-1.4% C, and composited with 10-20% WC and 5-10% silicon carbide (SiC) as a hard ceramic phase, with a layer thickness of 0.30-0.50 mm. In this layer, WC and the extremely hard SiC together form a rigid skeleton that resists abrasive wear, while the excellent thermal conductivity of SiC can effectively promote the diffusion of frictional heat to the lower and lateral layers, and suppress the generation of surface hot spots and hot cracks.

[0011] Optionally, a functional ceramic layer is located on the outermost layer. Its metallic binder phase consists of the remainder Co, 25-28% Cr, 5-7% Mo, 1.0-1.5% Si, and 0.5-0.8% C, and is composited with 10-20% Al2O3, 5-10% ZrO2, and 8-15% silicon carbide (SiC) as the functional ceramic phase. Simultaneously, 3-5% CaF2 or h-BN is added as a solid lubricant, with a layer thickness of 0.25-0.35 mm. This layer is crucial for performance: Al2O3 provides basic hardness and high-temperature oxidation resistance; ZrO2 significantly improves the coating's thermal shock resistance through a phase transformation toughening mechanism; and SiC serves as a high-temperature strength pillar and thermal conductivity network, maintaining extremely high strength and hardness above 1400°C, effectively resisting high-temperature softening and wear. Its high thermal conductivity, combined with the solid lubricant, ensures that the friction surface has a stable and excellent coefficient of friction and wear resistance under extreme conditions.

[0012] This invention also discloses a method for preparing the above-mentioned brake disc with a gradient wear-resistant ceramic composite coating, comprising the following steps: S1 Pretreatment steps: Surface cleaning and preheating of the brake disc substrate; S2 laser cladding steps: Laser cladding technology is used to sequentially clad a bonding transition layer, a hard support layer, and a functional ceramic layer on the pretreated substrate; S3 post-processing steps: slow cooling and surface finishing of the clad brake disc.

[0013] Furthermore, in the above preparation method, the laser cladding step is performed using a high-power laser under a protective atmosphere, and the thickness of each layer is controlled within the range described above.

[0014] The present invention also discloses a braking system, including a brake disc and brake pads that cooperate with the brake disc, wherein the brake disc is a brake disc with a gradient wear-resistant ceramic composite coating as described in the present invention.

[0015] The present invention also discloses a vehicle including a braking system, wherein the braking system is the braking system described above.

[0016] Compared with the prior art, the present invention has the following outstanding advantages: 1. Strong bonding and high reliability: Through the optimized transition layer, a high-strength metallurgical bond between the coating and the substrate is achieved, and thermal stress is effectively relieved, fundamentally preventing coating peeling.

[0017] 2. Excellent resistance to thermal degradation: By constructing a highly efficient heat-conducting network with SiC as the core in the coating, the heat dissipation capacity is significantly improved, local high temperature is avoided, and the stability of braking performance at high temperatures is ensured.

[0018] 3. Balanced comprehensive performance: Through the synergistic effect of multiphase ceramics (Al2O3, ZrO2, SiC) and solid lubricants, as well as gradient structure design, the coating has multiple advantages such as high wear resistance, high toughness, impact resistance and self-lubrication.

[0019] In summary, this invention, through its innovative gradient composite coating design, successfully solves the key problems of easy wear, heat fade, and coating peeling of traditional brake discs, providing a reliable solution for achieving high-performance, long-life braking systems. Attached Figure Description

[0020] Figure 1 A schematic diagram of the brake disc with a gradient wear-resistant ceramic composite coating according to the present invention. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1 A method for preparing a brake disc with a gradient wear-resistant ceramic composite coating includes the following steps: 1. Matrix pretreatment: The gray cast iron brake disc of grade HT250 was selected as the base.

[0023] The friction surface is roughened by sandblasting with brown fused alumina sand to achieve a surface roughness of Ra ≈ 6.3 μm, and oil and oxide scale are thoroughly removed.

[0024] The pretreated substrate is placed in a preheating furnace and kept at 300°C for 2 hours to reduce the thermal stress of subsequent laser cladding.

[0025] 2. Preparation of composite powder: The transition layer powder is made of Fe-based self-fluxing alloy, with the following composition by weight percentage: Fe balance, Cr 18%, Ni 10%, B 3.8%, Si 4.0%, and C 0.8%. The powder particle size ranges from 45 to 106 μm.

[0026] Hard support layer powder: A Co-based high-temperature alloy is used as the binder phase, and its composition by weight percentage is: Co balance, Cr 30%, W 4.5%, C 1.2%. This binder phase powder is mechanically mixed with 15 wt.% WC powder (particle size 2 μm) and 8 wt.% SiC powder (particle size 30 μm) for no less than 4 hours.

[0027] Functional ceramic layer powder: Co-based cermet is used as the binder phase, and its composition by weight percentage is: Co balance, Cr 26%, Mo 6%, Si 1.2%, C 0.6%. 15 wt.% Al2O3 (1 μm particle size), 8 wt.% ZrO2 (stabilized yttrium oxide, 0.5 μm particle size), 12 wt.% SiC (10 μm particle size), and 4 wt.% h-BN solid lubricant (10 μm particle size) are incorporated into this binder powder and thoroughly mixed.

[0028] 3. Laser cladding for gradient coatings: It employs a 3 kW fiber laser, equipped with a coaxial powder feeder and an inert gas protection system (argon, purity ≥99.99%).

[0029] Process parameters: laser power 2800 W, scanning speed 6 mm / s, spot diameter 3 mm, overlap rate 40%.

[0030] Cladding sequence: First, a bonding transition layer is clad onto the preheated substrate using a single-pass cladding process, with a controlled layer thickness of 0.20 mm.

[0031] After the transition layer is completed, a hard support layer is clad onto its surface, with the total layer thickness controlled at 0.40 mm.

[0032] Finally, a functional ceramic layer is clad onto the rigid support layer, with a controlled layer thickness of 0.30 mm.

[0033] The entire cladding process is carried out in a sealed processing chamber to ensure that the oxygen content is below 100 ppm.

[0034] 4. Post-processing: The brake discs that have been clad are immediately transferred to insulating sand and slowly cooled to room temperature (cooling rate of about 20°C / hour) to fully release residual stress.

[0035] Finally, the coated surface is precision ground using a diamond grinding wheel to ensure dimensional accuracy and surface roughness Ra ≤ 0.8 μm. The resulting product illustration is shown below. Figure 1 As shown.

[0036] Example 2 Brake disc fabrication based on Ni-based alloy system The main difference between this embodiment and Embodiment 1 is that a Ni-based system is used to combine the transition layer and the functional ceramic layer.

[0037] Bonding transition layer: A Ni-based alloy is used, with the following composition (by weight percentage): Ni balance, Cr 16%, Fe 5%, B 3.5%, Si 4.2%, C 0.7%. The layer thickness is controlled at 0.18 mm. This composition also exhibits excellent wettability and bonding strength with the gray cast iron matrix.

[0038] Rigid support layer: Same as in Example 1.

[0039] Functional ceramic layer: The binder phase is changed to Ni-based (Ni balance, Cr 25%, Mo 5%, Fe 5%). The composite ceramic phase and the type and ratio of solid lubricant are the same as in Example 1. The solid lubricant is CaF2.

[0040] The preparation process and parameters are basically the same as those in Example 1.

[0041] Example 3 Thick-coated brake discs suitable for heavy-duty vehicles This embodiment aims to verify the applicability of the present invention under heavy-load conditions.

[0042] The composition system of each layer is the same as that in Example 1.

[0043] Layer thickness control: The bonding transition layer was increased to 0.25 mm, the rigid support layer to 0.50 mm, and the functional ceramic layer to 0.35 mm. The total coating thickness reached 1.1 mm.

[0044] Process adjustments: To obtain a thicker, defect-free coating, the laser cladding parameters were adjusted appropriately: the laser power was increased to 3200 W, the powder feeding rate was increased accordingly, and the scanning speed was slightly reduced to 5 mm / s.

[0045] Example 4 Braking systems including the aforementioned brake discs and their vehicle applications The gradient-coated brake disc prepared in Example 1 was assembled into the front ventilated disc brake of a certain model SUV.

[0046] The matching component is a low-metal formula brake pad.

[0047] The braking system was integrated into the vehicle for subsequent road performance testing.

[0048] Test case To verify the beneficial effects of the present invention, comparative tests are conducted below.

[0049] Test sample: Sample A (of the present invention): Gradient ceramic composite coated brake disc prepared in Example 1.

[0050] Sample B (traditional comparative example): HT250 gray cast iron brake disc without any coating treatment.

[0051] Sample C (existing technology comparative example): Brake disc with an Al2O3-13%TiO2 ceramic coating (coating thickness approximately 0.3 mm) prepared using atmospheric plasma spraying (APS) technology.

[0052] Test Example 1 Coating bond strength and toughness assessment Test methods: The coating bond strength tensile test was conducted according to ASTM C633 standard; acoustic emission technology was used to monitor crack formation during the indentation test and to evaluate the coating toughness.

[0053] The results are shown in Table 1: Table 1 Evaluation of Coating Bond Strength and Toughness Conclusion: This invention achieves a metallurgical bonding strength far exceeding that of thermal spray coatings through laser cladding and gradient design, and the coating system also exhibits good toughness and strong impact resistance.

[0054] Test Example 2 Abrasion resistance tests at room temperature and high temperature Test method: Disc-block friction and wear test was conducted on an MM-2000 wear testing machine. The load was 100 N, the sliding speed was 0.84 m / s, and the total sliding distance was 10 km. High-temperature testing was conducted at 400°C. Wear was measured by weighing.

[0055] The results are shown in Table 2: Table 2 Abrasion resistance tests at room temperature and high temperature Conclusion: The brake disc of the present invention exhibits excellent and stable wear resistance at both room temperature and high temperature, with wear amount far lower than that of traditional cast iron and ordinary ceramic coating.

[0056] Test Example 3 Thermal degradation resistance and frictional stability test Test method: Continuous emergency braking was simulated on an inertial braking test bench. The initial braking speed was 100 km / h, the braking deceleration was 0.45g, and the braking cycle was repeated 10 times. The friction coefficient at the end of each braking cycle was recorded.

[0057] result: Conclusion: Sample A exhibited a highly stable coefficient of friction and an extremely low decay rate (<5%) throughout the test, demonstrating excellent resistance to thermal degradation. Samples B and C, however, both showed significant thermal degradation.

[0058] Test Example 4 Thermal conductivity and thermal management capability assessment Test methods: The thermal diffusivity of the coating material was measured using the laser flash method; the temperature field distribution on the surface of the brake disc was recorded using an infrared thermal imager during bench testing.

[0059] result: The thermal diffusivity of sample A (functional ceramic layer) is about 60% higher than that of sample C (Al2O3-TiO2 coating).

[0060] Conclusion: The SiC introduced in this invention constructs an effective heat-conducting network inside the coating, which significantly improves heat dissipation capacity and avoids local overheating, which is the key to achieving resistance to thermal degradation.

[0061] Test Example 5 Real-world road durability and mating component compatibility testing Test method: Test vehicles equipped with various sample brake discs were subjected to a 50,000-kilometer durability test under comprehensive urban road conditions. After the test, the wear of the brake discs and brake pads was measured.

[0062] The results are shown in Table 3: Table 3. Real-vehicle road durability and mating component compatibility test sample Average wear depth of brake disc (mm) Wear of paired brake pads (mm) A   0.08       0.35       B   0.75       0.55       C   0.22 (but localized peeling occurred) 0.68 (abnormal wear) Conclusion: The brake disc of this invention (sample A) not only has a service life far exceeding that of traditional products, but also has stable friction characteristics due to the presence of solid lubricant on its surface, which can effectively reduce wear on the brake pads. It achieves the systematic advantage of "protecting itself while taking care of its counterpart", resulting in significant comprehensive economic benefits.

[0063] It is worth noting that the above description of the embodiments focuses on illustrating the technical solution of the present invention, rather than precisely defining its scope of protection. Those skilled in the art should understand that appropriate adjustments and optimizations can be made based on the technical details disclosed in the embodiments of the present invention, or equivalent substitutions can be implemented for individual or even all technical elements. Such adjustments and substitutions will not deviate from the core essence of the technical solution of the present invention and should be included within the technical protection scope of the embodiments of the present invention. In short, the protection of the present invention should not be limited to the concrete presentation of the above embodiments, but broadly covers all equivalent changes and improvements that do not depart from its basic concept. In summary, the protection definition of the present invention should be based on the statement of the claims, and the above embodiments are only used as a reference guide for understanding the present invention.

Claims

1. A brake disc having a gradient wear resistant ceramic composite coating comprising a brake disc substrate (4) characterised in that: On the friction surface of the brake disc substrate (4), three layers of ceramic composite coatings with different functions are prepared in sequence by laser cladding technology to form a gradient composite structure, from inside to outside, in sequence, a bonding transition layer (1), a hard support layer (2) and a functional ceramic layer (3).

2. The brake disc of claim 1, wherein: The bonding transition layer (1) adopts Fe-based or Ni-based alloy, and the composition is as follows in terms of weight percentage: Fe balance, Cr 15-20%, Ni 8-12%, B 3.0-4.5%, Si 3.5-4.5%, C 0.6-1.0%, and the layer thickness is 0.15-0.25 mm.

3. The brake disc of claim 1, wherein: The hard support layer (2) uses Co-based or Ni-based high-temperature alloy as the binder phase, and is compounded with 10-20% WC and 5-10% SiC as the hard ceramic phase, and the layer thickness is 0.30-0.50 mm.

4. The brake disc of claim 1, wherein: The functional ceramic layer (3) uses Co-based or Ni-based cermet as the binder phase, and is compounded with 10-20% Al2O3, 5-10% ZrO2, 8-15% SiC and 3-5% solid lubricant, the solid lubricant is CaF2 or h-BN, and the layer thickness is 0.25-0.35 mm.

5. The brake disc of claim 1, wherein: The total thickness of the gradient composite coating is 0.7-1.1 mm.

6. The brake disc of claim 1, wherein: The brake disc substrate (4) is gray cast iron material.

7. A method of manufacturing a brake disc having a gradient wear resistant ceramic composite coating according to any one of claims 1 to 6, characterised in that, The method comprises the following steps: S1 pretreatment step: surface cleaning and preheating of the brake disc substrate; S2 laser cladding step: using laser cladding technology to sequentially clad the bonding transition layer, the hard support layer and the functional ceramic layer on the pretreated substrate; S3 post-treatment step: slow cooling treatment and surface finishing of the cladded brake disc.

8. The method of claim 7, wherein, The laser cladding step is carried out under a protective atmosphere using a high-power laser, and the thickness of each layer is controlled within the range described in claims 2-4.

9. A brake system comprising a brake disc and a brake pad cooperating with the brake disc, characterized in that The brake disc is a brake disc with a gradient wear-resistant ceramic composite coating as claimed in any one of claims 1-6.

10. A vehicle comprising a brake system, characterized in that The brake system is a brake system as claimed in claim 9.

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