Brake disc surface gradient wear-resistant layer and preparation method thereof

Abstract

The invention discloses a brake disc surface gradient wear-resistant layer and a preparation method thereof, and belongs to the technical field of brake disc coatings, and the brake disc surface gradient wear-resistant layer sequentially comprises a transition layer, a heat-resistant layer, a wear-resistant bottom layer and a wear-resistant surface layer from bottom to top; a preparation raw material of the transition layer is a heat-resistant alloy; the preparation raw materials of the heat-resistant layer are heat-resistant alloy and quaternary carbide; and the wear-resistant bottom layer and the wear-resistant surface layer are prepared from wear-resistant alloy and quaternary carbide. The preparation method comprises the steps that S2, transition layer raw material powder is welded to the surface of the brake disc through plasma surfacing, and a transition layer can be formed on the surface of the brake disc after annealing; s3, heat-resistant layer raw material powder is deposited on the surface of the transition layer through laser cladding to form a heat-resistant layer; and S4, sequentially depositing the wear-resistant bottom layer raw material powder and the wear-resistant surface layer raw material powder on the surface of the heat-resistant layer through laser cladding, and tempering to obtain the gradient wear-resistant layer on the surface of the brake disc. The gradient wear-resistant layer on the surface of the brake disc has good strength performance and good wear resistance at high temperature.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of brake disc coating, and particularly relates to a brake disc surface gradient wear-resistant layer and a preparation method thereof. BACKGROUND

[0002] The automobile brake disc is a core component of the braking system, and its performance directly affects driving safety and service life. At present, the mainstream brake disc material is gray cast iron, which has low cost and good thermal conductivity, but has problems of insufficient wear resistance and poor high-temperature oxidation resistance. During braking, the surface temperature of the brake disc instantaneously rises, and at the same time, it bears high-frequency friction and wear and thermal shock, which easily causes cracks, excessive wear and even failure, and thus needs to be replaced regularly.

[0003] In the prior art, in order to improve the performance of the brake disc, surface coating technology is often used, such as plasma spray welding, laser cladding and the like to prepare a wear-resistant layer. However, the traditional coating has the following defects: the bonding strength between the coating and the gray cast iron substrate is low, the interface is prone to peeling due to poor material compatibility; a single coating is difficult to balance the heat resistance and wear resistance, and is prone to softening or oxidation at high temperature; the distribution of carbide reinforcing phases is uneven, resulting in large fluctuations in the performance of the coating; and the preparation process parameters and material properties are not matched, which easily causes defects such as pores and cracks. SUMMARY

[0004] The application provides a brake disc surface gradient wear-resistant layer and a preparation method thereof to overcome the above technical problems. The brake disc surface gradient wear-resistant layer provided by the application has good strength performance and good high-temperature wear resistance.

[0005] The application solves the above technical problems through the following technical solutions.

[0006] The application discloses a brake disc surface gradient wear-resistant layer, which comprises, from bottom to top, a transition layer, a heat-resistant layer, a wear-resistant bottom layer and a wear-resistant surface layer. The preparation raw material of the transition layer is a heat-resistant alloy; the preparation raw material of the heat-resistant layer is a heat-resistant alloy and a quaternary carbide; and the preparation raw material of the wear-resistant bottom layer and the wear-resistant surface layer is a wear-resistant alloy and a quaternary carbide. According to mass percentage, the composition of the heat-resistant alloy comprises 9% to 15% of Cr, 2.0% to 4.0% of Al, 2.5% to 5.0% of Mo and 1.8% to 3.2% of Ni. According to mass percentage, the composition of the wear-resistant alloy comprises 14% to 20% of Cr, 3.5% to 7.0% of Ni and 2.0% to 4.0% of Mo. The composition of the quaternary carbide is (Nb a Ti b W c Ta 1-a-c)C; wherein, in terms of molar ratio, a=0.10~0.20, b=0.10~0.20, c=0.10~0.20.

[0007] According to some embodiments of the present application, the brake disc is made of gray cast iron; In terms of mass fraction, the composition of the heat-resistant alloy is: 0.12%~0.28% C, 10%~13% Cr, 2.2%~3.2% Al, 3.2%~4.2% Mo, 1.8%~3.2% Ni, 1.4%~2.6% Si, 0.7%~1.3% Mn, 0.4%~0.9% Nb, 0.4%~1.1% Cu, and the balance is Fe and inevitable impurities. In terms of mass fraction, the composition of the wear-resistant alloy is: 0.15%~0.20% C, 16.0%~18.0% Cr, 4.0%~6.0% Ni, 2.5%~3.5% Mo, 0.8%~1.2% V, 0.5%~0.8% Ti, 0.05%~0.1% B, 0.03%~0.05% Ce, and the balance is Fe and inevitable impurities.

[0008] The composition of the quaternary carbide is (Nb a Ti b W c Ta 1-a-c )C; wherein, in terms of molar ratio, a=0.10~0.20, b=0.10~0.20, c=0.10~0.20.

[0009] According to some embodiments of the present application, in terms of mass fraction, the raw material for preparing the heat-resistant layer is 15~25% quaternary carbide and the balance is heat-resistant alloy; preferably, the raw material for preparing the heat-resistant layer is 18~22% quaternary carbide and the balance is heat-resistant alloy. The heat-resistant alloy has good compatibility with the gray cast iron matrix, and combined with the high-temperature stability of the quaternary carbide, it resists the softening and oxidation of the coating at the moment of high temperature during braking.

[0010] According to some embodiments of the present application, in terms of mass fraction, the raw material for preparing the wear-resistant bottom layer is 25~35% quaternary carbide and the balance is wear-resistant alloy; preferably, the raw material for preparing the wear-resistant bottom layer is 28~32% quaternary carbide and the balance is wear-resistant alloy. The wear-resistant alloy realizes the functional progression from transition heat resistance to high wear resistance through the gradient increase of carbide content.

[0011] According to some embodiments of the present application, in terms of mass fraction, the raw material for preparing the wear-resistant surface layer is 35~45% quaternary carbide and the balance is wear-resistant alloy; preferably, the raw material for preparing the wear-resistant bottom layer is 38~42% quaternary carbide and the balance is wear-resistant alloy.

[0012] According to some embodiments of the present application, the thickness of the transition layer is 0.3-0.6 mm, preferably 0.4-0.5 mm.

[0013] According to some embodiments of the present application, the thickness of the heat-resistant layer, the wear-resistant surface layer and the wear-resistant bottom layer is 0.7-1.5 mm, preferably 0.8-1.2 mm.

[0014] According to some embodiments of the present application, the hardness HV0.5 of the brake disc is ≥550, preferably 570-610 at 25℃.

[0015] According to some embodiments of the present application, the hardness HV0.5 of the brake disc is ≥460, preferably 480-505 at 500℃.

[0016] According to some embodiments of the present application, the wear rate of the surface gradient wear-resistant layer of the brake disc is ≤1.1E-4 mm 3 / N·m, preferably 7.5E-5-9.2E-5 mm 3 / N·m The preparation method of the aforementioned surface gradient wear-resistant layer of the brake disc comprises the following steps: S1. Raw material preparation: grind the heat-resistant alloy, the wear-resistant alloy and the quaternary carbide, then mix the powders according to the required ratio of each layer to obtain the transition layer raw material powder, the heat-resistant layer raw material powder, the wear-resistant bottom layer raw material powder and the wear-resistant surface layer raw material powder; S2. Preparation of the transition layer: the transition layer raw material powder is plasma surfacing on the surface of the brake disc, and the transition layer is formed on the surface of the brake disc after annealing; S3. Preparation of the heat-resistant layer: the heat-resistant layer raw material powder is deposited on the surface of the aforementioned transition layer by laser cladding to form the heat-resistant layer; S4. Preparation of the wear-resistant layer: the wear-resistant bottom layer raw material powder and the wear-resistant surface layer raw material powder are deposited on the surface of the aforementioned heat-resistant layer by laser cladding in sequence, and the surface gradient wear-resistant layer of the brake disc is obtained after tempering.

[0017] In S1, the brake disc needs to be pretreated, i.e. the gray cast iron disc is deoiled at 380-420℃ for 1-2 h, and then sandblasted with brown corundum so that the surface roughness Ra of the brake disc is 5-10 μm.

[0018] In S1, the D50 of the quaternary carbide is 20-50 μm.

[0019] In S1, the preparation method of the quaternary carbide: TiO2 powder, Nb2O5 powder, Ta2O5 powder, W powder and carbon black are sintered at 2200-2300℃ for 4-6 h.

[0020] In S1, the D50 of the heat-resistant alloy is 80~120μm.

[0021] In S1, the D50 of the wear-resistant alloy is 50~80μm.

[0022] In S2, the transition layer is made of plasma welding. The high bonding strength of the welding ensures the metallurgical bond between the transition layer and the substrate, while the protective gas reduces porosity.

[0023] In S2, the voltage for plasma welding is 18~22V, preferably 19~21V.

[0024] In S2, the plasma welding speed is 150~200 mm / min, preferably 160~190 mm / min.

[0025] In S2, the plasma welding is performed under a protective atmosphere of 2-6 vol% H2 and the remainder argon, with a flow rate of 14-22 L / min; preferably, the plasma welding is performed under a protective atmosphere of 3-5 vol% H2 and the remainder argon, with a flow rate of 16-18 L / min.

[0026] In S2, the annealing is performed in a vacuum furnace; the vacuum degree is ≤5×10⁻⁶. -3 Below Pa; hold at 550~650℃ for 1~3h, then cool with the furnace to below 200℃ before unloading. Preferably, hold at 580~620℃ for 1.5~2.5h, then cool with the furnace to below 200℃ before unloading.

[0027] In S3 and S4, the high energy density of the laser is used to precisely control the temperature of the molten pool, avoiding excessive burning of the quaternary carbides and achieving coating densification.

[0028] In S3, the power of the laser cladding is 2.0~3.0kW, preferably 2.4~2.6kW.

[0029] In S3, the scanning speed of the laser cladding is 600~700mm / min, preferably 620~680mm / min.

[0030] In S3, the powder feeding rate of the laser cladding is 12~20g / min, preferably 15~17g / min.

[0031] In S3, the temperature of the molten pool for laser cladding is 1600~1750℃, preferably 1660~1700℃.

[0032] In S4, the power of the laser cladding is 2.5~3.5kW, preferably 2.8~3.4kW; In S4, the scanning speed of the laser cladding is 400~600mm / min, preferably 450~550mm / min.

[0033] In S4, the powder feeding rate of the laser cladding is 18~24 g / min, preferably 18~22 g / min.

[0034] In S4, the temperature of the molten pool for laser cladding is 1700~1780℃, preferably 1700~1740℃.

[0035] In S4, the tempering is performed by cooling to 180-240°C at a cooling rate of 0.5-2.5°C / s; preferably, the tempering is performed by cooling to 200-220°C at a cooling rate of 1.0-2.0°C / s.

[0036] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0037] Compared with the prior art, the beneficial effects of the present invention are: 1. The four-layer gradient structure of the present invention achieves a smooth transition of performance from substrate to transition to heat resistance to wear resistance, which avoids the interface peeling between the traditional coating and the substrate, and takes into account both high temperature heat resistance and room temperature wear resistance, thus meeting the requirements of high frequency friction and instantaneous high temperature extreme working conditions of brake disc.

[0038] 2. The combined process of plasma welding and laser cladding utilizes the high bonding strength and efficiency of plasma welding, while the precise temperature control of laser cladding ensures coating densification and retention of the reinforcing phase. Combined with the optimization of parameters such as annealing and tempering, the coating defect rate is reduced, and the preparation cost is lowered. Attached Figure Description

[0039] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0040] Figure 1 This is a schematic diagram of the structure of the gradient wear-resistant layer on the surface of the brake disc of the present invention.

[0041] Figure 2 This is a scanning electron microscope image of the gradient wear-resistant layer on the surface of the brake disc prepared in Example 1.

[0042] Explanation of reference numerals in the attached diagram: 1. Brake disc; 2. Transition layer; 3. Heat-resistant layer; 4. Wear-resistant bottom layer; 5. Wear-resistant surface layer. Detailed Implementation

[0043] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0044] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0045] The "range" disclosed in this invention is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be combined arbitrarily; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is understood that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this invention, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein; "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer greater than or equal to 2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0047] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0048] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0049] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0050] Unless otherwise specified, the term "or" is inclusive in this invention. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0051] The raw material information used in the following examples is as follows: The brake disc is made of gray cast iron, grade HT250; The heat-resistant alloy has a D50 of 98 μm by mass fraction, and its composition is 0.17% C, 12.8% Cr, 2.75% Al, 3.42% Mo, 2.47% Ni, 1.58% Si, 0.86% Mn, 0.57% Nb, 0.83% Cu, with the balance being Fe and unavoidable impurities. The wear-resistant alloy has a D50 of 63 μm by mass fraction, and its composition is 0.16% C, 17.2% Cr, 5.3% Ni, 2.79% Mo, 0.91% V, 0.74% Ti, 0.085% B, 0.048% Ce, with the balance being iron and unavoidable impurities. The preparation process of quaternary carbides: TiO2 powder, Nb2O5 powder, Ta2O5 powder, W powder, and carbon black are ball-milled and mixed for 10 hours to obtain a mixture; the mixture is poured into a mold and pressed under a 100t press for 4 minutes, then heated to 2300℃ in a carbon tube furnace and sintered at this temperature for 5 hours. After cooling to room temperature in the furnace, a block is obtained; the block is ball-milled to obtain a composition of (Ti 0.15 Nb 0.15 Ta 0.15 W 0.55 The carbon black is a quaternary carbide with a D50 of 25 μm. The molar ratio of carbon in carbon black to the total molar ratio of titanium, tantalum, niobium, and tungsten in the powder is 1:1. Example 1 In this embodiment, the gradient wear-resistant layer on the brake disc surface consists of, from bottom to top, a transition layer, a heat-resistant layer, a wear-resistant underlayer, and a wear-resistant surface layer. See the schematic diagram below. Figure 1 The thickness of the transition layer is 0.47 mm, and the thicknesses of the heat-resistant layer, wear-resistant underlayer, and wear-resistant surface layer are 0.88 mm. See the scanning electron microscope image for details. Figure 2 ; The transition layer is made of heat-resistant alloy; The raw materials for preparing the heat-resistant layer consist of 20 wt% heat-resistant alloy and the balance quaternary carbides; The raw materials for preparing the wear-resistant bottom layer consist of 30wt% wear-resistant alloy and the balance quaternary carbide; The raw materials for preparing the wear-resistant surface layer consist of 40wt% wear-resistant alloy and the balance quaternary carbides.

[0052] The method for preparing the gradient wear-resistant layer on the surface of the brake disc in this embodiment is as follows: S1. Raw material preparation: After ball milling heat-resistant alloy, wear-resistant alloy and quaternary carbide, the raw materials prepared above are mixed according to the required ratio of each layer to obtain transition layer raw material powder, heat-resistant layer raw material powder, wear-resistant bottom layer raw material powder and wear-resistant surface layer raw material powder respectively. The brake disc was kept at 400℃ for 1 hour to remove oil, and then sandblasted with brown corundum to make the surface roughness Ra of the brake disc 6.7μm.

[0053] S2. Preparation of transition layer: The transition layer raw material powder is plasma-deposited onto the surface of the brake disc under the protection of 4.3 vol% H2 and the balance argon gas. The flow rate of the protection gas is 18 L / min, the plasma deposition voltage is 20 V, and the plasma deposition speed is 180 mm / min. After welding, anneal in a vacuum furnace with a vacuum degree ≤5×10 -3 Under Pa, the temperature is kept at 610℃ for 2 hours, and then cooled in the furnace to below 200℃ before being taken out of the furnace, which can form a transition layer on the surface of the brake disc. S3. Preparation of heat-resistant layer: Heat-resistant layer raw material powder is deposited on the surface of the above transition layer by laser cladding. The laser cladding power is 2.5kW, the scanning speed is 650mm / min, the powder feeding rate is 15g / min, and the molten pool temperature is 1680℃, and then the heat-resistant layer is formed. S4. Preparation of wear-resistant layer: The wear-resistant bottom layer raw material powder and the wear-resistant top layer raw material powder are sequentially deposited on the surface of the above heat-resistant layer by laser cladding. The laser cladding power is 3.2kW, the scanning speed is 490mm / min, the powder feeding rate is 20.5g / min, and the molten pool temperature is 1720℃. The brake disc surface gradient wear-resistant layer is obtained by cooling it to 220℃ at a cooling rate of 2.0℃ / s for tempering, and then naturally cooling it to room temperature (25℃).

[0054] Example 2 The difference between this embodiment and Embodiment 1 is as follows: The raw materials for preparing the heat-resistant layer consist of 15 wt% heat-resistant alloy and the balance quaternary carbide; The other raw materials, structure, steps and parameters are the same as in Example 1.

[0055] Example 3 The difference between this embodiment and Embodiment 1 is as follows: The raw materials for preparing the wear-resistant bottom layer consist of 40wt% wear-resistant alloy and the balance quaternary carbide; The raw materials for preparing the wear-resistant surface layer consist of 50 wt% wear-resistant alloy and the balance quaternary carbides.

[0056] The other raw materials, structure, steps and parameters are the same as in Example 1.

[0057] Example 4 The difference between this embodiment and Embodiment 1 is as follows: In this embodiment, the thickness of the transition layer of the gradient wear-resistant layer on the brake disc surface is 0.3 mm, and the thickness of the heat-resistant layer, the wear-resistant bottom layer, and the wear-resistant top layer is 1.2 mm. The other raw materials, structure, steps and parameters are the same as in Example 1.

[0058] Example 5 The difference between this embodiment and Embodiment 1 is as follows: During the preparation of the heat-resistant layer in S3, the power of laser cladding is 2.0kW; During the preparation of the wear-resistant layer in S4, the power of laser cladding is 3.0kW; The other raw materials, structure, steps and parameters are the same as in Example 1.

[0059] Example 6 The difference between this embodiment and Embodiment 1 is as follows: In S4, the temperature is cooled to 200°C and tempered at a rate of 5°C / s. The other raw materials, structure, steps and parameters are the same as in Example 1.

[0060] Comparative Example 1 The difference between this comparative example and Example 1 is as follows: This comparative example does not contain a transition layer, and therefore does not include step S2. All other raw materials, structures, steps, and parameters are the same as in Example 1.

[0061] Comparative Example 2 The difference between this comparative example and Example 1 is as follows: This comparative example does not contain a heat-resistant layer, and therefore does not include step S3. Other raw materials, structures, steps and parameters are the same as in Example 1.

[0062] Comparative Example 3 The difference between this comparative example and Example 1 is as follows: (Ti 0.3 Nb 0.3 W 0.4 C, other raw materials, structures, steps and parameters are the same as in Example 1.

[0063] Comparative Example 4 The difference between this comparative example and Example 1 is as follows: S2. The transition layer is also prepared by laser cladding instead of plasma welding. The laser cladding power of S2 is 2.2 kW, the scanning speed is 580 mm / min, and the powder feeding rate is 15 g / min. Other raw materials, structures, steps and parameters are the same as in Example 1.

[0064] Comparative Example 5 The difference between this comparative example and Example 1 is as follows: In the preparation of the transition layer in S2, the transition layer is formed without annealing after welding; other raw materials, structures, steps and parameters are the same as in Example 1.

[0065] Test case The performance of the gradient wear-resistant layer on the surface of the brake disc prepared in the above embodiments and comparative examples was tested, and the test results are shown in Table 1.

[0066] The Vickers hardness test was performed according to GB / T 4340.3-2025, with test temperatures of 25℃ and 500℃; the HV0.5 of the brake disc at 25℃ was 218. The wear rate was measured using a UMT-2 reciprocating friction and wear tester from Bruker (Bruker UMT, USA); SiN balls were used as the grinding pair, the friction load was 2000N, the friction frequency was 900Hz, the friction radius was 2mm, and the time was set to 30s. The friction coefficients at 25°C and 500°C were tested using a friction coefficient tester.

[0067]

[0068] Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this invention can be purchased commercially or prepared using existing methods. The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this invention. It should be understood that the above descriptions are merely specific embodiments of this invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A surface gradient wear layer for a brake disc, characterised in that, From bottom to top are transition layer, heat-resistant layer, wear-resistant bottom layer and wear-resistant surface layer; The transition layer is made of heat-resistant alloy; The heat-resistant layer is made of heat-resistant alloy and quaternary carbide; The wear-resistant bottom layer and the wear-resistant surface layer are made of wear-resistant alloy and quaternary carbide; The heat-resistant alloy comprises, by mass percentage, 9-15% Cr, 2.0-4.0% Al, 2.5-5.0% Mo, 1.8-3.2% Ni; The wear-resistant alloy comprises, by mass percentage, 14-20% Cr, 3.5-7.0% Ni, 2.0-4.0% Mo; The composition of the quaternary carbide is (Nb a Ti b W c Ta 1-a-c )C; wherein, in terms of molar ratio, a=0.10~0.20, b=0.10~0.20, c=0.10~0.

20.

2. A brake disc surface gradient wear layer according to claim 1, wherein, At least one of the following conditions a-d is met: a. The brake disc is made of gray cast iron; b. The heat-resistant alloy comprises, by mass percentage, 0.12-0.28% C, 10-13% Cr, 2.2-3.2% Al, 3.2-4.2% Mo, 1.8-3.2% Ni, 1.4-2.6% Si, 0.7-1.3% Mn, 0.4-0.9% Nb, 0.4-1.1% Cu, and the balance of Fe and inevitable impurities; c. The wear-resistant alloy comprises, by mass percentage, 0.15-0.20% C, 16.0-18.0% Cr, 4.0-6.0% Ni, 2.5-3.5% Mo, 0.8-1.2% V, 0.5-0.8% Ti, 0.05-0.1% B, 0.03-0.05% Ce, and the balance of Fe and inevitable impurities; d. the quaternary carbide has a composition of (Nb a Ti b W c Ta 1-a-c )C, in a molar ratio of a = 0.10-0.16, b = 0.10-0.16, and c = 0.10-0.

16.

3. A brake disc surface gradient wear layer according to claim 2, wherein, At least one of the following conditions a-c is met: a. The heat-resistant layer is made of 15-25% quaternary carbide and the balance of heat-resistant alloy by mass percentage; preferably, the heat-resistant layer is made of 18-22% quaternary carbide and the balance of heat-resistant alloy; b. The wear-resistant bottom layer is made of 25-35% quaternary carbide and the balance of wear-resistant alloy by mass percentage; preferably, the wear-resistant bottom layer is made of 28-32% quaternary carbide and the balance of wear-resistant alloy; c. The wear-resistant surface layer is made of 35-45% quaternary carbide and the balance of wear-resistant alloy by mass percentage; preferably, the wear-resistant bottom layer is made of 38-42% quaternary carbide and the balance of wear-resistant alloy.

4. The brake disc surface gradient wear layer of claim 1, wherein, At least one of the following conditions a-b is met: a. The thickness of the transition layer is 0.3-0.6 mm, preferably 0.4-0.5 mm; b. The thickness of the heat-resistant layer, the wear-resistant surface layer and the wear-resistant bottom layer is 0.7-1.5 mm, preferably 0.8-1.2 mm.

5. The brake disc surface gradient wear layer of claim 1, wherein, At least one of the following conditions a-c is met: a. The hardness HV0.5 of the brake disc at 25℃ is ≥550; b. The hardness HV0.5 of the brake disc at 500℃ is ≥460; c. the brake disc surface gradient wear layer has a wear rate of <1.1E-4 mm 3 / N·m.

6. A method of producing a surface gradient wear layer for a brake disc as claimed in any one of claims 1 to 5, wherein, The method comprises the following steps: S1. Raw material preparation: grind the heat-resistant alloy, wear-resistant alloy and quaternary carbide for standby, and mix the powders according to the required proportion of each layer to obtain transition layer raw material powder, heat-resistant layer raw material powder, wear-resistant bottom layer raw material powder and wear-resistant surface layer raw material powder respectively; S2. Preparing the transition layer: the transition layer raw material powder is plasma surfacing to the surface of the brake disc, and the transition layer is formed on the surface of the brake disc after annealing; S3. Preparing the heat-resistant layer: the heat-resistant layer raw material powder is deposited on the surface of the transition layer by laser cladding to form the heat-resistant layer; S4. Preparing the wear-resistant layer: the wear-resistant bottom layer raw material powder and the wear-resistant surface layer raw material powder are sequentially deposited on the surface of the heat-resistant layer by laser cladding, and the surface gradient wear-resistant layer of the brake disc is obtained after tempering.

7. A method of producing a surface gradient wear layer for a brake disc as claimed in claim 6, characterised in that, The S1 satisfies at least one of the following conditions a-e: a. The brake disc needs to be pretreated, that is, the gray cast iron disc is deoiled at 380-420℃ for 1-2h, and then sandblasted with brown corundum, so that the surface roughness Ra of the brake disc is 5-10μm; b. The D50 of the quaternary carbide is 20-50μm; c. The preparation method of the quaternary carbide: TiO2 powder, Nb2O5 powder, Ta2O5 powder, W powder and carbon black are sintered at 2200-2300℃ for 4-6h; d. The D50 of the heat-resistant alloy is 80-120μm; e. The D50 of the wear-resistant alloy is 50-80μm.

8. A method of producing a surface gradient wear layer for a brake disc as claimed in claim 6, characterised in that, The S2 satisfies at least one of the following conditions a-d: a. The voltage of the plasma surfacing is 18-22V, preferably 19-21V; b. The speed of the plasma surfacing is 150-200mm / min, preferably 160-190mm / min c. The plasma surfacing is carried out under the protection of 2-6vol% H2 and the balance of argon as the protective gas, and the flow rate of the protective gas is 14-22L / min; preferably, the plasma surfacing is carried out under the protection of 3-5vol% H2 and the balance of argon as the protective gas, and the flow rate of the protective gas is 16-18L / min; d. The annealing is processed in a vacuum furnace; the vacuum degree is ≤5x10 -3 Pa; annealing at 550-650℃ for 1-3h, and then furnace cooling to below 200℃ before discharging; preferably, annealing at 580-620℃ for 1.5-2.5h, and then furnace cooling to below 200℃ before discharging.

9. The method of claim 6, wherein the surface gradient wear layer is formed by a process comprising: The S3 satisfies at least one of the following conditions a-d: ​ a. The power of the laser cladding is 2.0-3.0kW, preferably 2.4-2.6kW; b. The scanning speed of the laser cladding is 600-700mm / min, preferably 620-680mm / min; c. The powder feeding rate of the laser cladding is 12-20g / min, preferably 15-17g / min; d. The molten pool temperature of the laser cladding is 1600-1750℃, preferably 1660-1700℃.

10. The method of claim 6, wherein the surface gradient wear layer is formed by a process comprising: The S4 satisfies at least one of the following conditions a-e: ​ a. The power of the laser cladding is 2.5-3.5kW, preferably 2.8-3.4kW; b. The scanning speed of the laser cladding is 400-600mm / min, preferably 450-550mm / min; c. The powder feeding rate of the laser cladding is 18-24g / min, preferably 18-22g / min; d. The molten pool temperature of the laser cladding is 1700-1780℃, preferably 1700-1740℃; e. the tempering is cooling to 180 to 240°C at a cooling rate of 0.5 to 2.5°C / s; preferably, the tempering is cooling to 200 to 220°C at a cooling rate of 1.0 to 2.0°C / s.

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