Method for preparing carbide coating on surface of bipolar plate

Abstract

The invention provides a method for preparing a carbide coating on the surface of a bipolar plate, and relates to the technical field of metal surface treatment. According to the method for preparing the carbide coating on the surface of the bipolar plate, the bipolar plate base body is preheated and activated, then the Ti metal transition layer and the TiC ceramic coating are prepared based on the magnetron sputtering technology, stress between the TiC ceramic coating and the bipolar plate base body is eliminated by applying the Ti metal transition layer, and the problems that the carbide coating on the surface of the base body is corroded, falls off and the like are solved; therefore, the prepared coating has the advantages of high hardness, good corrosion resistance, good chemical stability and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface treatment, and in particular relates to a method for preparing a carbide coating on the surface of a bipolar plate. Background Art

[0002] In the prior art, metal carbides used in the field of fuel cells can be used as modified materials applied to the surface of stainless steel bipolar plates due to their high electrical conductivity and high chemical stability. However, metal carbide coatings are easily corroded and fall off in some highly corrosive media, and are relatively brittle. Under stress, they are prone to cracking, which accelerates failure and further affects the conductivity. In addition, the technology of applying a single-layer carbide coating on the surface of metal parts is prone to internal stress due to the thin carbide layer prepared and the poor thermal expansion matching between the carbide and the metal matrix, which leads to the carbide coating falling off and other problems, further deteriorating the conductivity. Therefore, how to achieve application in the field of fuel cells and prepare a carbide coating on the metal surface so that it can meet both the high corrosion protection requirements and the conductivity requirements is a technical problem that needs to be solved urgently by those skilled in the art.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] The present invention aims to provide a method for preparing a carbide coating on the surface of a bipolar plate, so as to improve the above-mentioned problems existing in the prior art.

[0005] In order to achieve the above purpose, the following technical solutions are adopted:

[0006] The first object of the present invention is to provide a method for preparing a carbide coating on the surface of a bipolar plate, comprising the following steps:

[0007] S1. The bipolar plate substrate is placed in a magnetron sputtering device, and then the bipolar plate substrate is preheated under vacuum conditions, and then argon gas is introduced to bombard and activate it;

[0008] S2. Depositing a Ti metal transition layer on the surface of the activated bipolar plate substrate by magnetron sputtering technology;

[0009] S3. Depositing a TiC ceramic coating on the surface of the Ti metal transition layer away from the bipolar plate substrate by magnetron sputtering technology to form a composite coating comprising a Ti metal transition layer and a TiC ceramic coating on the surface of the bipolar plate substrate.

[0010] Further, based on the above technical solution of the present invention, the bipolar plate substrate includes a stainless steel substrate;

[0011] And / or, before the bipolar plate substrate is placed in the magnetron sputtering device, the method further includes the steps of grinding, cleaning, drying and sandblasting the surface of the bipolar plate substrate.

[0012] Furthermore, on the basis of the above technical solution of the present invention, sandpaper with different mesh sizes is used to polish the surface of the bipolar plate substrate step by step;

[0013] And / or, sand blasting with 80-200 grit blasting grit.

[0014] Further, on the basis of the above technical solution of the present invention, in step S1, the preheating temperature is 380-420°C, and the preheating time is 15-25min;

[0015] And / or, in step S1, the activation time is 35-45 min, and the argon flow rate is 45-55 ml / min.

[0016] Furthermore, based on the above technical solution of the present invention, in step S2, a Ti target is used as a sputtering target during magnetron sputtering to deposit a Ti metal transition layer in an argon atmosphere.

[0017] Furthermore, on the basis of the above technical solution of the present invention, in step S2, at least one of the following process parameters is adopted in the process of magnetron sputtering deposition of the Ti metal transition layer: the argon flow rate is 45-55 ml / min, preferably 50 ml / min; and / or, the gas pressure is 0.1-0.3 Pa; and / or, the Ti target current is 40-50 A; and / or, the negative bias voltage loaded on the bipolar plate substrate is -200 to -300 V; and / or, the deposition time is 10 to 20 min.

[0018] Furthermore, on the basis of the above technical solution of the present invention, in step S3, a TiC target is used as a sputtering target in a magnetron sputtering process to deposit a TiC ceramic coating in an argon atmosphere.

[0019] Further, on the basis of the above technical solution of the present invention, in step S3, at least one of the following process parameters is adopted in the process of magnetron sputtering deposition of TiC ceramic coating: argon flow rate is 45-55ml / min, preferably 50ml / min; and / or, gas pressure is 0.1-0.3Pa; and / or, TiC target current is 75-85A; and / or, negative bias voltage loaded on bipolar plate substrate is -300~-400V; and / or, deposition time is 1-1.5h.

[0020] Further, based on the above technical solution of the present invention, the thickness of the Ti metal transition layer is 0.2-0.3 μm;

[0021] And / or, the thickness of the TiC ceramic coating is 6-8 μm.

[0022] The second object of the present invention is to provide a composite coating on the surface of a bipolar plate, which is prepared by the method for preparing a carbide coating on the surface of a bipolar plate provided by the first object of the present invention;

[0023] The composite coating comprises a Ti metal transition layer and a TiC ceramic coating arranged sequentially from the inside to the outside on the surface of the bipolar plate substrate;

[0024] Preferably, the composite coating has a composition gradient structure.

[0025] Compared with the prior art, the technical solution of the present invention has at least the following technical effects:

[0026] (1) The present invention provides a method for preparing a carbide coating on the surface of a bipolar plate. The bipolar plate substrate is first preheated and activated, and then a Ti metal transition layer and a TiC ceramic coating are prepared based on a magnetron sputtering technology. By applying the Ti metal transition layer, the stress between the carbide layer (TiC ceramic coating) and the bipolar plate substrate is eliminated, and the problem of corrosion and shedding of the carbide coating on the substrate surface is solved, so that the prepared coating has the advantages of high hardness, good corrosion resistance and good chemical stability.

[0027] (2) The present invention provides a composite coating on the surface of a bipolar plate, wherein the composite coating includes a Ti metal transition layer and a TiC ceramic coating sequentially arranged on the surface of a bipolar plate substrate from the inside to the outside, wherein the Ti metal transition layer effectively reduces the difference in physical and chemical properties between the bipolar plate substrate and the TiC ceramic coating, thereby avoiding the situation where the TiC ceramic coating is directly in contact with the bipolar plate substrate and is prone to cracking and poor interface bonding, so that the TiC ceramic coating can be better integrated with the bipolar plate substrate through the intermediate metal transition layer (Ti metal transition layer), having good bonding performance, and the TiC ceramic coating itself also has good electrical conductivity, thereby effectively solving the problem of the prior art of preparing a ceramic coating on a bipolar plate substrate, which is prone to cracking and thus accelerates failure, causing the carbide coating to fall off, and further affecting the electrical conductivity and deteriorating the electrical conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The polarization curve of a stainless steel substrate having only a TiC ceramic coating formed on the surface in a dilute H2SO4 solution in the prior art;

[0029] Figure 2 This is the polarization curve of the stainless steel substrate with the composite coating formed on the surface of the present invention in a dilute H2SO4 solution. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. The process parameters of the following embodiments that do not specify specific conditions are usually based on conventional conditions.

[0031] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0032] In order to better solve the density problem of the fusion of metal materials and ceramic coatings in the prior art, which leads to the decrease of the corrosion resistance and conductivity of the overall structure, the present invention is specially proposed.

[0033] According to a first aspect of the present invention, there is provided a method for preparing a carbide coating on the surface of a bipolar plate, comprising the following steps:

[0034] S1. The bipolar plate substrate is placed in a magnetron sputtering device, and then the bipolar plate substrate is preheated under vacuum conditions, and then argon gas is introduced to bombard and activate it;

[0035] S2. Depositing a Ti metal transition layer on the surface of the activated bipolar plate substrate by magnetron sputtering technology;

[0036] S3. Depositing a TiC ceramic coating on the surface of the Ti metal transition layer away from the bipolar plate substrate by magnetron sputtering technology to form a composite coating comprising a Ti metal transition layer and a TiC ceramic coating on the surface of the bipolar plate substrate.

[0037] Specifically, in step S1 of the present invention, the bipolar plate substrate is preheated under vacuum conditions, which is conducive to a better combination of the bipolar plate substrate and the coating. Then, argon gas is introduced to bombard and activate the substrate, which is conducive to improving the deposition effect of the subsequent coating and obtaining a coating with better deposition quality.

[0038] In step S2 and step S3 of the present invention, a Ti metal transition layer and a TiC ceramic coating are prepared based on magnetron sputtering technology, respectively. The Ti metal transition layer effectively weakens the difference in physical and chemical properties between the bipolar plate substrate and the TiC ceramic coating, and avoids the situation that the TiC ceramic coating is prone to cracks and poor interface bonding when it directly contacts the bipolar plate substrate, so that the TiC ceramic coating can be better integrated with the bipolar plate substrate through the Ti metal transition layer, and has good bonding performance. The TiC ceramic coating itself also has good electrical conductivity, thereby well solving the problem of easy cracks and accelerated failure caused by preparing the ceramic coating on the bipolar plate substrate in the prior art, resulting in the carbide coating falling off, thereby affecting the electrical conductivity and deteriorating the electrical conductivity.

[0039] As an optional implementation of the technical solution of the present invention, the bipolar plate substrate is a metal substrate, preferably a stainless steel substrate.

[0040] As an optional implementation of the technical solution of the present invention, before the bipolar plate substrate is placed in the magnetron sputtering device, it also includes the steps of grinding, cleaning, drying and sandblasting the surface of the bipolar plate substrate.

[0041] Among them, the grinding of the bipolar plate substrate is mainly to remove its surface oxide layer. The subsequent sandblasting is mainly to ensure the surface uniformity of the subsequent deposition.

[0042] As an optional implementation of the technical solution of the present invention, sandpapers with different mesh sizes (such as 300 mesh, 500 mesh, 1000 mesh, and 1500 mesh sandpaper) are used to polish the surface of the bipolar plate substrate step by step.

[0043] As an optional implementation of the technical solution of the present invention, 80-200 mesh sand blasting sand is used for sand blasting to ensure the uniformity of the surface of the bipolar plate substrate after sand blasting.

[0044] As an optional implementation scheme of the technical solution of the present invention, in step S1, the preheating temperature is 380-420°C, for example, 380°C, 390°C, 400°C, 410°C or 420°C, preferably 400°C, and the preheating time is 15-25min, for example, 15min, 18min, 20min, 22min or 25min, preferably 20min.

[0045] If the preheating temperature or preheating time exceeds the above range, a better coating deposition effect cannot be obtained.

[0046] As an optional implementation scheme of the technical solution of the present invention, in step S1, the activation time is 35-45 min, for example, 35 min, 38 min, 40 min, 42 min or 45 min, preferably 40 min, and the argon flow rate is 45-55 ml / min, for example, 45 ml / min, 48 ml / min, 50 ml / min, 52 ml / min or 55 ml / min, etc., preferably 50 ml / min.

[0047] If the activation time or the argon flow rate exceeds the above numerical range, a good activation effect may not be achieved. As an optional implementation of the technical solution of the present invention, in step S2, a Ti target is used as a sputtering target during magnetron sputtering to deposit a Ti metal transition layer in an argon atmosphere.

[0048] The present invention deposits the Ti metal transition layer under an argon atmosphere, which can ensure that the deposited coating has good compactness and can effectively improve the bonding between layers. The Ti metal transition layer, as an intermediate layer, has better bonding with both the bipolar plate substrate and the external TiC ceramic coating, and will not cause the coating to fall off. Compared with other atmospheres, such as nitrogen, titanium nitride will be generated when titanium and nitrogen are combined, and other impurities may be generated during the generation process. Titanium nitride itself will affect the compactness of the coating, and titanium nitride will also affect the bonding of the interface between the coatings (such as the bonding between titanium nitride and the bipolar plate substrate, and the bonding between titanium nitride and the external TiC ceramic coating), which ultimately leads to the shedding of the coating.

[0049] As an optional implementation of the technical solution of the present invention, in step S2, at least one of the following process parameters is used during magnetron sputtering deposition of the Ti metal transition layer:

[0050] The argon gas flow rate is 45-55 ml / min, for example, 45 ml / min, 48 ml / min, 50 ml / min, 52 ml / min or 55 ml / min, etc., preferably 50 ml / min;

[0051] and / or, the air pressure is 0.1-0.3 Pa, for example, 0.1 Pa, 0.2 Pa or 0.3 Pa, etc., preferably 0.1 Pa;

[0052] and / or, the Ti target current is 40-50A, for example, 40A, 42A, 44A, 45A, 48A or 50A, etc., preferably 40A;

[0053] and / or, the bipolar plate substrate is loaded with a negative bias voltage of -200 to -300 V;

[0054] And / or, the deposition time is 10-20 min, for example, 10 min, 12 min, 15 min, 16 min, 18 min or 20 min, etc., preferably 15 min.

[0055] By further limiting the above process parameters, the magnetron sputtering coating deposition effect is improved. At the same time, by controlling the changes of the above process parameters during magnetron sputtering, the coating can have a composition gradient structure, for example, a gradient coating with dense top and sparse bottom can be formed.

[0056] As an optional implementation of the technical solution of the present invention, in step S3, a TiC target is used as a sputtering target during magnetron sputtering to deposit a TiC ceramic coating in an argon atmosphere.

[0057] As an optional implementation of the technical solution of the present invention, in step S3, at least one of the following process parameters is used during magnetron sputtering deposition of the TiC ceramic coating:

[0058] The argon gas flow rate is 45-55 ml / min, for example, 45 ml / min, 48 ml / min, 50 ml / min, 52 ml / min or 55 ml / min, etc., preferably 50 ml / min;

[0059] And / or, the air pressure is 0.1-0.3 Pa, such as 0.1 Pa, 0.2 Pa or 0.3 Pa;

[0060] and / or, the TiC target current is 75-85A, for example, 75A, 78A, 80A, 82A or 85A, etc., preferably 80A;

[0061] and / or, the TiC target power is 1000W;

[0062] and / or, the bipolar plate substrate is loaded with a negative bias voltage of -300 to -400 V;

[0063] And / or, the deposition time is 1-1.5 h, for example, 1 h, 1.2 h or 1.5 h, etc., preferably 1 h.

[0064] By further limiting the above process parameters, the process is made simple and controllable, and the quality of the deposited coating is better. The coating can also have a composition gradient structure by controlling the changes in the above process parameters during magnetron sputtering, for example, the density of the coating gradually increases or decreases from the inside to the outside.

[0065] As an optional implementation of the technical solution of the present invention, the thickness of the Ti metal transition layer is 0.2 to 0.3 μm. The thickness of the Ti metal transition layer should not be too thin (less than 0.2 μm), otherwise it cannot achieve the corresponding performance effect; the thickness of the Ti metal transition layer should not be too thick (more than 0.3 μm), otherwise it is easy to generate internal stress, resulting in cracks in the coating. Therefore, the typical but non-restrictive thickness of the Ti metal transition layer is 0.2 μm, 0.22 μm, 0.24 μm, 0.25 μm, 0.26 μm, 0.28 μm or 0.3 μm, etc.

[0066] As an optional embodiment of the technical solution of the present invention, the thickness of the TiC ceramic coating is 6-8 μm. Typical but non-limiting thicknesses of the TiC ceramic coating are 6 μm, 6.2 μm, 6.5 μm, 6.8 μm, 7 μm, 7.2 μm, 7.5 μm, 7.8 μm or 8 μm.

[0067] As a preferred embodiment of the technical solution of the present invention, the method for preparing a carbide coating on the surface of a bipolar plate comprises the following steps:

[0068] S1. The metal substrate is polished with 300 mesh, 500 mesh, 1000 mesh, and 1500 mesh sandpaper in a grinding machine to remove the surface oxide layer, wiped with acetone and blown dry, and then placed in an ultrasonic device for ultrasonic cleaning. After the cleaning is completed, it is blown dry and sandblasted until it loses its gloss, wherein the sandblasting grit size is between 80 and 200;

[0069] Place the treated metal substrate on the support of the magnetron sputtering equipment and evacuate the magnetron sputtering chamber to 1×10 -4 Pa, and turn on the power to preheat the metal substrate to 400°C and maintain it for 20 minutes, then introduce 99.99% pure argon gas to bombard the metal substrate surface for 40 minutes to activate the metal substrate surface, and the Ar flow rate is controlled at 50ml / min.

[0070] S2. After the metal substrate surface is activated, turn on the power of the Ti target, apply a negative bias voltage to the bipolar plate substrate, and magnetron sputter deposit a Ti metal transition layer on the metal substrate surface. During the magnetron sputtering process of depositing the Ti metal transition layer, the Ar flow rate is 50 ml / min, the gas pressure is 0.1-0.3 Pa, the Ti target current is 40-50 A, the negative bias voltage loaded on the metal substrate is -200--300 V, the deposition time is 10-20 min, and the thickness of the Ti metal transition layer is 0.2-0.3 μm.

[0071] S3. After obtaining a Ti metal transition layer with a thickness of 0.2 to 0.3 μm, turn on the power of the TiC target, and use magnetron sputtering technology to deposit a TiC ceramic coating on the Ti metal transition layer to form a final composite coating. In the process of forming and depositing the TiC ceramic coating by magnetron sputtering, the Ar flow rate is 50 ml / min, the gas pressure is 0.1 to 0.3 Pa, the negative bias voltage loaded by the magnetron sputtering TiC ceramic coating is -300 to -400 V, the magnetron sputtering TiC target power is 1000 W, the TiC target current is 80 A, the deposition time is 1 hour, and the thickness of the TiC ceramic coating is 6 to 8 μm.

[0072] According to a second aspect of the present invention, there is also provided a carbide coating on the surface of a bipolar plate, which is prepared by the method for preparing a carbide coating on the surface of a bipolar plate provided by the first object of the present invention;

[0073] The composite coating comprises a Ti metal transition layer and a TiC ceramic coating which are sequentially arranged on the surface of the bipolar plate substrate from the inside to the outside.

[0074] As an optional embodiment of the present invention, the composite coating has a composition gradient structure.

[0075] By applying a Ti metal transition layer, the stress between the TiC ceramic coating and the bipolar plate substrate is eliminated, and the problems of corrosion and shedding of the carbide coating on the substrate surface are solved, so that the prepared coating has the advantages of high hardness, good corrosion resistance and good chemical stability.

[0076] The present invention will be further described in detail below with reference to specific embodiments and comparative examples.

[0077] Example 1

[0078] This embodiment provides a method for preparing a carbide coating on the surface of a bipolar plate, comprising the following steps:

[0079] S1. The stainless steel substrate is polished with a polishing machine and 300 mesh, 500 mesh, 1000 mesh and 1500 mesh sandpaper are used to polish and remove the surface oxide layer. After wiping with acetone and blowing dry, it is placed in an ultrasonic device for ultrasonic cleaning. After cleaning, it is blown dry and sandblasted until it loses its luster. The sandblasting grit size is between 80-200.

[0080] Place the treated stainless steel substrate on the support of the magnetron sputtering equipment and evacuate the magnetron sputtering chamber to 1×10 -4 Pa, and turn on the power to preheat the stainless steel substrate to 400℃ and maintain it for 20min, then introduce argon gas with a purity of 99.99% to bombard the surface of the stainless steel substrate for 40min, so as to activate the surface of the stainless steel substrate, and the Ar flow rate is controlled at 50ml / min.

[0081] S2. After step S1, turn on the power of the Ti target, apply a negative bias voltage to the stainless steel substrate, and deposit a Ti metal transition layer on the surface of the stainless steel substrate by magnetron sputtering. During the process of forming and depositing the Ti metal transition layer by magnetron sputtering, the Ar flow rate is 50 ml / min, the gas pressure is 0.1 Pa, the Ti target current is 40 A, the negative bias voltage loaded on the stainless steel substrate is -200 to -300 V, the deposition time is 15 min, and the thickness of the Ti metal transition layer is 0.2 μm.

[0082] S3. After obtaining a Ti metal transition layer with a thickness of 0.2 μm, turn on the power of the TiC target, and use magnetron sputtering technology to deposit a TiC ceramic coating on the Ti metal transition layer to form a final composite coating. In the process of forming and depositing the TiC ceramic coating by magnetron sputtering, the Ar flow rate is 50 ml / min, the gas pressure is 0.1 Pa, the negative bias voltage loaded by the magnetron sputtering TiC ceramic coating is -300 V, the magnetron sputtering TiC target power is 1000 W, the TiC target current is 80 A, the deposition time is 1 h, and the thickness of the TiC ceramic coating is 6 μm.

[0083] Example 2

[0084] This embodiment provides a method for preparing a carbide coating on the surface of a bipolar plate, comprising the following steps:

[0085] S1. The stainless steel substrate is polished with a polishing machine and 300 mesh, 500 mesh, 1000 mesh and 1500 mesh sandpaper are used to polish and remove the surface oxide layer. After wiping with acetone and blowing dry, it is placed in an ultrasonic device for ultrasonic cleaning. After cleaning, it is blown dry and sandblasted until it loses its luster. The sandblasting grit size is between 80-200.

[0086] Place the treated stainless steel substrate on the support of the magnetron sputtering equipment and evacuate the magnetron sputtering chamber to 1×10 -4 Pa, and turn on the power to preheat the stainless steel substrate to 400℃ and maintain it for 20min, then introduce argon gas with a purity of 99.99% to bombard the surface of the stainless steel substrate for 40min, so as to activate the surface of the stainless steel substrate, and the Ar flow rate is controlled at 50ml / min.

[0087] S2. After step S1, turn on the power of the Ti target, apply a negative bias voltage to the stainless steel substrate, and deposit a Ti metal transition layer on the surface of the stainless steel substrate by magnetron sputtering. During the process of forming and depositing the Ti metal transition layer by magnetron sputtering, the Ar flow rate is 50 ml / min, the gas pressure is 0.1 Pa, the Ti target current is 40 A, the negative bias voltage loaded on the stainless steel substrate is -200 V, the deposition time is 20 min, and the thickness of the Ti metal transition layer is 0.3 μm.

[0088] S3. After obtaining a Ti metal transition layer with a thickness of 0.3 μm, turn on the power of the TiC target, and use magnetron sputtering technology to deposit a TiC ceramic coating on the Ti metal transition layer to form a final composite coating. In the process of forming and depositing the TiC ceramic coating by magnetron sputtering, the Ar flow rate is 50 ml / min, the gas pressure is 0.2 Pa, the negative bias voltage loaded by the magnetron sputtering TiC ceramic coating is -400 V, the magnetron sputtering TiC target power is 1000 W, the TiC target current is 80 A, the deposition time is 1 h, and the thickness of the TiC ceramic coating is 7 μm.

[0089] Example 3

[0090] This embodiment provides a method for preparing a carbide coating on the surface of a bipolar plate, comprising the following steps:

[0091] S1. The stainless steel substrate is polished with a polishing machine and 300 mesh, 500 mesh, 1000 mesh and 1500 mesh sandpaper are used to polish and remove the surface oxide layer. After wiping with acetone and blowing dry, it is placed in an ultrasonic device for ultrasonic cleaning. After cleaning, it is blown dry and sandblasted until it loses its luster. The sandblasting grit size is between 80-200.

[0092] Place the treated stainless steel substrate on the support of the magnetron sputtering equipment and evacuate the magnetron sputtering chamber to 1×10 -4 Pa, and turn on the power to preheat the stainless steel substrate to 400℃ and maintain it for 20min, then introduce argon gas with a purity of 99.99% to bombard the surface of the stainless steel substrate for 40min, so as to activate the surface of the stainless steel substrate, and the Ar flow rate is controlled at 50ml / min.

[0093] S2. After step S1, turn on the power of the Ti target, apply a negative bias voltage to the stainless steel substrate, and deposit a Ti metal transition layer on the surface of the stainless steel substrate by magnetron sputtering. During the process of forming and depositing the Ti metal transition layer by magnetron sputtering, the Ar flow rate is 50 ml / min, the gas pressure is 0.1 Pa, the Ti target current is 40 A, the negative bias voltage loaded on the stainless steel substrate is -200 V, the deposition time is 15 min, and the thickness of the Ti metal transition layer is 0.26 μm.

[0094] S3. After obtaining a Ti metal transition layer with a thickness of 0.26 μm, turn on the power of the TiC target, and use magnetron sputtering technology to deposit a TiC ceramic coating on the Ti metal transition layer to form a final composite coating. In the process of forming and depositing the TiC ceramic coating by magnetron sputtering, the Ar flow rate is 50 ml / min, the gas pressure is 0.3 Pa, the negative bias voltage loaded by the magnetron sputtering TiC ceramic coating is -400 V, the magnetron sputtering TiC target power is 1000 W, the TiC target current is 80 A, the deposition time is 1 h, and the thickness of the TiC ceramic coating is 8 μm.

[0095] Comparative Example 1

[0096] This comparative example provides a method for preparing a carbide coating on the surface of a bipolar plate, which is a comparative example of Example 1. Compared with Example 1, this comparative example does not set a Ti metal transition layer between the stainless steel substrate and the TiC ceramic coating, and specifically includes the following steps:

[0097] S1. The stainless steel substrate is polished with a polishing machine and 300 mesh, 500 mesh, 1000 mesh and 1500 mesh sandpaper are used to polish and remove the surface oxide layer. After wiping with acetone and blowing dry, it is placed in an ultrasonic device for ultrasonic cleaning. After cleaning, it is blown dry and sandblasted until it loses its luster. The sandblasting grit size is between 80-200.

[0098] Place the treated stainless steel substrate on the support of the magnetron sputtering equipment and evacuate the magnetron sputtering chamber to 1×10 -4 Pa, and turn on the power to preheat the stainless steel substrate to 400℃ and maintain it for 20min, then introduce argon gas with a purity of 99.99% to bombard the surface of the stainless steel substrate for 40min, so as to activate the surface of the stainless steel substrate, and the Ar flow rate is controlled at 50ml / min.

[0099] S2. After step S1, turn on the power of the TiC target, and use magnetron sputtering technology to deposit a TiC ceramic coating on the surface of the stainless steel substrate. In the process of forming and depositing the TiC ceramic coating by magnetron sputtering, the Ar flow rate is 50 ml / min, the gas pressure is 0.1 Pa, the negative bias voltage loaded by the magnetron sputtering TiC ceramic coating is -300 V, the magnetron sputtering TiC target power is 1000 W, the TiC target current is 80 A, the deposition time is 1 h, and the thickness of the TiC ceramic coating is 6 μm.

[0100] In order to compare the technical effects of the above embodiments and comparative examples, the following experimental examples are specially designed.

[0101] The stainless steel substrate with only TiC ceramic coating formed on the surface prepared in Comparative Example 1 and the stainless steel substrate with composite coating formed on the surface provided in Example 1 were tested in a fuel cell simulation environment (0.3M dilute H2SO4 solution). The polarization curves of the two substrates are shown as follows: Figure 1 and Figure 2 shown. Figure 1 and Figure 2 The polarization curve results in Fig. 3 show that the composite coating improves the corrosion resistance of the base metal, especially under acidic conditions, the effect is more obvious.

[0102] Compared with the metal substrate, the corrosion potential of the composite coating is increased by more than 250 mV relative to the metal substrate (the optimal corrosion potential is increased to more than 260 mV). It can be seen that the application of metal stainless steel materials in the field of fuel cells is promoted by applying the coating.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are within the scope of protection of the pending claims of the present invention.

Claims

1. A method for preparing a carbide coating on the surface of a bipolar plate, characterized in that: The following steps are involved: S1. The bipolar plate substrate is placed in a magnetron sputtering device, and then the bipolar plate substrate is preheated under vacuum conditions, and then argon gas is introduced to bombard and activate it; S2. Depositing a Ti metal transition layer on the surface of the activated bipolar plate substrate by magnetron sputtering technology; S3. Depositing a TiC ceramic coating on the surface of the Ti metal transition layer away from the bipolar plate substrate by magnetron sputtering technology to form a composite coating comprising a Ti metal transition layer and a TiC ceramic coating on the surface of the bipolar plate substrate.

2. The method for preparing a carbide coating on the surface of a bipolar plate according to claim 1, characterized in that: The bipolar plate substrate comprises a stainless steel substrate; And / or, before the bipolar plate substrate is placed in the magnetron sputtering device, the method further includes the steps of grinding, cleaning, drying and sandblasting the surface of the bipolar plate substrate.

3. The method for preparing a carbide coating on the surface of a bipolar plate according to claim 2, characterized in that: The surface of the bipolar plate substrate is polished step by step using sandpaper of different mesh sizes; And / or, sand blasting with 80-200 grit blasting grit.

4. The method for preparing a carbide coating on the surface of a bipolar plate according to claim 1, characterized in that: In step S1, the preheating temperature is 380-420°C and the preheating time is 15-25 minutes; And / or, in step S1, the activation time is 35-45 min, and the argon flow rate is 45-55 ml / min.

5. The method for preparing a carbide coating on the surface of a bipolar plate according to claim 1, characterized in that: In step S2, a Ti target is used as a sputtering target during magnetron sputtering, and a Ti metal transition layer is deposited in an argon atmosphere.

6. The method for preparing a carbide coating on the surface of a bipolar plate according to claim 5, characterized in that: In step S2, during the magnetron sputtering deposition of the Ti metal transition layer, at least one of the following process parameters is used: the argon flow rate is 45-55 ml / min, preferably 50 ml / min; and / or the gas pressure is 0.1-0.3 Pa; and / or the Ti target current is 40-50 A; and / or the negative bias voltage loaded on the bipolar plate substrate is -200 to -300 V; and / or the deposition time is 10-20 min.

7. The method for preparing a carbide coating on the surface of a bipolar plate according to claim 1, characterized in that: In step S3, a TiC target is used as a sputtering target material during magnetron sputtering, and a TiC ceramic coating is deposited in an argon atmosphere.

8. The method for preparing a carbide coating on the surface of a bipolar plate according to claim 7, characterized in that: In step S3, during the magnetron sputtering deposition of the TiC ceramic coating, at least one of the following process parameters is used: an argon flow rate of 45-55 ml / min, preferably 50 ml / min; and / or a gas pressure of 0.1-0.3 Pa; and / or a TiC target current of 75-85 A; and / or a negative bias voltage of -300 to -400 V loaded on the bipolar plate substrate; and / or a deposition time of 1-1.5 h.

9. The method for preparing a carbide coating on the surface of a bipolar plate according to any one of claims 1 to 8, characterized in that: The thickness of the Ti metal transition layer is 0.2-0.3 μm; And / or, the thickness of the TiC ceramic coating is 6-8 μm.

10. A composite coating on the surface of a bipolar plate, characterized in that: The method for preparing a carbide coating on the surface of a bipolar plate according to any one of claims 1 to 9 is used to prepare the carbide coating; The composite coating comprises a Ti metal transition layer and a TiC ceramic coating arranged sequentially from the inside to the outside on the surface of the bipolar plate substrate; Preferably, the composite coating has a composition gradient structure.

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