JP2006318652A - Solid oxide type fuel cell separator material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid oxide type fuel cell separator material which excels in an electrical conductivity at 600°C or more and steam oxidation resistance, and in which a Cr evaporation is also suppressed. <P>SOLUTION: The solid oxide type fuel cell separator material is a separator material in which a TiN coating layer having a thickness of 0.05-100 μm is formed to a ferrite stainless steel of 11-40 mass% of Cr, and a Ti concentration of the TiN coating layer is adjusted to more than 40 atom%. The ferrite stainless steel contains C: below 0.1 mass%, N: below 0.1 mass%, Si: below 1.5 mass%, Mn: below 1.5 mass%, P: below 0.10 mass%, and S: below 0.01 mass%, in addition to the Cr. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solid oxide fuel cell separator material that is excellent in electrical conductivity and oxidation resistance in a high temperature range of 600 ° C. or higher and suppresses chromium poisoning.

In order to cope with the depletion of fossil fuels typified by petroleum and the global warming phenomenon caused by CO ₂ emissions, there is a demand for practical use of a new system that replaces the conventional power generation system. A typical new power generation system is a fuel cell, which is expected to be deployed as a clean power generation system in distributed power sources, automotive power sources, and the like.
Various fuel cells have been introduced in the past. Among them, the solid oxide fuel cell (SOFC) has the highest energy efficiency and is a power generation system that is expected to be put to practical use.

  In conventional solid oxide fuel cells (SOFC), ceramics are mainly used as constituent members because of a high operating temperature of about 1000 ° C., and it has been very difficult to use metal materials. However, in recent years, it has become possible to lower the operating temperature to about 600 to 800 ° C. by improving the solid electrolyte membrane. Along with the decrease in operating temperature, metal materials such as high Cr / high Ni austenitic stainless steel having excellent high-temperature oxidation resistance can be applied.

The required properties of a solid oxide fuel cell (SOFC) separator material with reduced operating temperature are good electrical conductivity (less than 30 mΩ · cm ² ), oxidation resistance, and ceramics in the temperature range of 600 to 800 ° C. The thermal expansion coefficient (about 13 × 10 ⁻⁶ (1 / K) at room temperature to 800 ° C.) equivalent to that of the system solid oxide. For applications where start / stop is frequently repeated, heat fatigue resistance is also required.

  High Cr / High Ni austenitic stainless steel, which has excellent resistance to steam oxidation at high temperatures, has a very high coefficient of thermal expansion. Therefore, in applications where start-up and stop are frequently repeated, heat caused by thermal expansion / contraction Due to deformation and scale peeling, it cannot be used as a separator material for solid oxide fuel cells (SOFC). On the other hand, ferritic stainless steel is suitable as a separator material for solid oxide fuel cells because it exhibits a thermal expansion coefficient comparable to that of an electrolyte.

For example, C: 0.2 mass% or less, Si: less than 0.2 mass%, Mn: 1.0 mass% or less, Cr: 11-30 mass%, Ni: 2 mass% or less, Al: 1 mass% or less , Zr: not more than 1% by mass, Y: not more than 0.5% by mass and / or rare earth elements: not more than 0.2% by mass is known as a ferritic stainless steel for solid oxide fuel cell separators (patents) Reference 1). This stainless steel forms an oxide film with good electrical conductivity in the temperature range of 750 to 950 ° C., shows good oxidation resistance and scale peeling resistance even after prolonged use, and has a difference in thermal expansion from the electrolyte. Small is also an advantage.
JP 2003-105503 A

However, when a solid stainless steel material is used for the separator, an oxide is generated during the use of the solid oxide fuel cell, and the electrical resistance of the contact portion is increased. In order to eliminate power generation loss due to an increase in electrical resistance, it is necessary to further reduce the electrical conductivity of the separator material. Moreover, since all of the conventional stainless steels introduced as separators for solid oxide fuel cells basically have a high Cr content, an oxide scale with a high Cr concentration is likely to be generated. In the separator environment of a solid oxide fuel cell exposed to a steam atmosphere at 600 to 800 ° C., Cr on the oxide scale reacts with the water vapor to evaporate, and the solid oxide electrolyte is easily poisoned.
Although the reaction of Cr / water vapor can be suppressed by applying Ag or the like to the stainless steel surface, it is not economical because expensive noble metal elements are consumed. Therefore, the solid oxide fuel cell must be used while allowing the Cr to evaporate to some extent.

As a means for maintaining good oxidation resistance at high temperatures without requiring the use of expensive noble metal elements, it is known to apply a conductive oxide coating to stainless steel. For example, there is a solid oxide fuel cell using stainless steel coated with ZrO ₂ as a separator (Patent Document 2). Although ZrO ₂ coating provides good oxidation resistance, it has a high electrical resistance at high temperatures and is difficult to apply to the conductive part of the separator. In a polymer electrolyte fuel cell (PEFC) having a low operating temperature, a TiN coating containing an oxidation-inhibiting element (Patent Document 3) is known, but a film having a composition showing good electrical conduction at an operating temperature of 100 ° C. or lower is used. As will be described later, in the high temperature range of 600 ° C. or higher, many of them exhibit high electrical resistance, and the knowledge at room temperature is not helpful at all.
Japanese Patent Laid-Open No. 9-67672 Japanese Patent Laid-Open No. 2002-75398

As described above, steam oxidation resistance necessary for use in a high temperature range of 600 ° C. or higher, good electrical conductivity at high temperature, and durability in a solid oxide fuel cell environment where Cr evaporation must be suppressed Until now, no substantial study has been conducted on sex.
By specifying the Cr content of the ferritic stainless steel used for the base material and the type and composition of the ceramic film covering the base material surface, the present invention is resistant to steam oxidation, electrical conductivity at high temperatures, and resistance to Cr. An object of the present invention is to provide a solid oxide fuel cell separator material excellent in evaporability.

  The present invention uses a ferritic stainless steel containing Cr: 11 to 40% by mass as a base material, and forms a coating layer having a thickness of 0.05 to 100 μm covering the base material surface. The coating layer is characterized by being TiN having a Ti concentration of 40 atomic% or more. The Cr concentration and the V, Zr, Al concentration of the TiN coating layer are limited to Cr <10 atomic% and V + Zr + Al <10 atomic% as required.

The ferritic stainless steel used for the base material is preferably Cr: 11-40 mass%, C: 0.1 mass% or less, N: 0.1 mass% or less, Si: 1.5 mass% or less, Mn: 1.5% by mass or less, P: 0.10% by mass or less, S: 0.01% by mass or less, and the balance substantially has a composition of Fe.
As needed, Mo: 0.1-4.0 mass%, W: 0.1-4.0 mass%, Nb: 0.05-0.80 mass%, Ti: 0.03-0.50 mass %, Cu: 0.1 to 4.0% by mass, Zr: 0.03 to 0.50% by mass, Ta: 0.03 to 0.50% by mass, Al: 0.02 to 0.20% by mass, Y: 0.0005-0.1% by mass, REM (rare earth elements such as La, Ce, Nd): 0.0005-0.1% by mass, Ca: 0.0005-0.01% by mass, B: 0 One kind or two kinds or more of 0.0002 to 0.01% by mass can be contained.

Effects and embodiments of the invention

  When solid stainless steel is applied to the separator, when exposed to the high-temperature steam atmosphere (600 to 800 ° C.) of the fuel cell, oxidation progresses easily, and the electrical resistance of the conductive portion increases. Function is impaired. Moreover, the solid electrolyte is poisoned by the evaporated Cr. It is considered that an increase in electrical resistance and poisoning of the solid electrolyte are suppressed by applying a coating showing conductivity at high temperatures to stainless steel. Therefore, the inventors focused on a method of forming a TiN coating layer on ferritic stainless steel.

The electrical resistance of the main component Cr ₂ O ₃ of the oxide film formed on the stainless steel surface is about 10 ³ to 10 ² at 700 ° C., and TiN shows an electrical resistance lower than Cr ₂ O ₃ at the same 700 ° C. Further, the TiN coating layer is provided with good oxidation resistance by using a ferritic stainless steel of Cr: 11 mass% or more as a base material, and also has an action of suppressing evaporation of Cr due to steam oxidation.

In a solid polymer electrolyte fuel cell having an operating temperature as low as about 80 ° C., there is a TiN-coated separator material (Patent Document 3), but a TiN coating layer containing an oxidation-inhibiting element is shown in Example 1 described later. In contrast, when exposed to a high temperature atmosphere of 600 ° C. or higher, the electrical conductivity is significantly increased. The increase in electrical conductivity is thought to be due to the fact that Al and V, which are effective as an oxidation inhibitor on the low temperature side, form an oxide film with high electrical resistance on the high temperature side.
In this regard, the TiN coating layer having a Ti concentration of 40 atomic% or more maintains good electrical conductivity in the temperature range of 600 to 800 ° C., and effectively suppresses evaporation of Cr due to steam oxidation. The effect of Ti concentration on maintaining high electrical conductivity and suppressing Cr evaporation is unpredictable from the solid polymer electrolyte type separator for fuel cells, and becomes prominent at 47 atomic% or more.

  When forming a TiN coating layer on stainless steel for a separator, the stability of the TiN coating layer is emphasized, and in particular, the TiN coating layer is required not to peel off. By the way, when austenitic stainless steel with a large thermal expansion coefficient is used as the base material, thermal stress is generated between the TiN coating layer and the base material, and the TiN coating layer peels off during use, especially when it is repeatedly started and stopped. Resulting in. On the other hand, when ferritic stainless steel having a Cr content of less than 11% by mass is used as the base material, although the coefficient of thermal expansion is small, the oxidation rate is fast and sometimes abnormal oxidation occurs. Abnormal oxidation can be prevented by setting the Cr content of the ferritic stainless steel to 11% by mass or more.

  The TiN coating layer is also required to have stability after a long time. There is a concern that Ti is more stable in oxide in the environment of use, diffuses between the base material component and the coating layer, and becomes a layer different from the initial TiN after a long time. However, when the present inventors investigated the structure of the coating layer after a long period of time, the TiN coating layer was transformed into a mixed layer of Fe, Ti spinel-based oxide and TiN, but the base layer diffused into the coating layer. The material component was mainly Fe, and it was found that no outward diffusion of Cr to the TiN side occurred. The coating layer after alteration is Fe and Ti spinel oxides and residual materials having electrical conductivity equal to or higher than that of Mn and Cr oxides produced when solid stainless steel is used as a separator material. Since it is made of TiN, good electrical conductivity is maintained, and it is also effective in suppressing Cr evaporation. The suppression of Cr diffusion by the TiN coating layer is an effect that cannot be predicted from the TiN coating layer applied to the solid polymer fuel cell separator material, and imparts characteristics suitable for the solid oxide fuel cell to the separator material.

Hereinafter, the components, contents, and TiN coating layers of the ferritic stainless steel used for the base material of the solid oxide fuel cell separator will be described individually.
[C, N: 0.1% by mass or less]
Although it is an effective component for improving high-temperature strength, especially creep properties, excessive addition significantly reduces the workability and low-temperature toughness of ferritic stainless steel. Moreover, it reacts with TI and Nb to easily generate carbonitrides, and reduces solute Ti and solute Nb effective in improving high temperature strength. Therefore, in this component system, it is preferable that the C and N contents are small, and the upper limit is set to 0.1% by mass in both cases.

[Si: 1.5% by mass or less]
It is an effective alloy component for stabilizing chromium-based oxides, and also exhibits an effect of improving the steam oxidation resistance. However, if an excessive amount of silicon exceeding 1.0% by mass is contained, a SiO ₂ oxide layer having a high electric resistance is formed on the surface layer of the substrate, and the electric conductivity is lowered. Excessive Si content reduces the low-temperature toughness of ferritic stainless steel, and also causes surface flaws on the steel sheet, thereby reducing productivity.
[Mn: 1.5% by mass or less]
Although it is a component that improves the scale peelability of ferritic stainless steel, if an excessive amount of Mn exceeding 1.5% by mass is contained, the steel material becomes hard, and the workability and low temperature toughness deteriorate.
[S: 0.01 mass% or less]
It is a component that adversely affects hot workability and weld hot cracking resistance, and also serves as a starting point for abnormal oxidation. Therefore, the S content is preferably as low as possible, and the upper limit is set to 0.01% by mass.

[Cr: 11-40% by mass]
It is an indispensable alloy component for imparting the necessary corrosion resistance, oxidation resistance and electrical conductivity to stainless steel. In order to ensure steam oxidation resistance and good electrical conductivity at around 600 ° C., the Cr content was set to 11% by mass or more. In particular, when considering exposure to a water vapor atmosphere, a Cr content of 20% by mass or more is preferable. However, excessive addition of Cr adversely affects the workability, low temperature toughness, and 475 ° C. embrittlement susceptibility of ferritic stainless steel, so the upper limit of Cr content was set to 40% by mass.

[Mo, W, Cu: 0.1-4.0% by mass]
Mo and W are alloy components that improve high temperature strength and heat fatigue resistance by solid solution strengthening and Cu by solid solution strengthening or precipitation strengthening, where creep strength due to lamination or thermal fatigue due to repeated start / stop is a problem , Added as needed. However, since the steel material is excessively hardened when excessively added, the upper limit is set to 4.0% by mass in any case.

[Nb: 0.05 to 0.80 mass%, Ti: 0.03 to 0.50 mass%, Zr: 0.05 to 0.50 mass%, V: 0.03 to 0.50 mass%, Ta : 0.03 to 0.50% by mass]
It is an alloy component added as necessary, and further improves the high temperature strength of ferritic stainless steel by solid solution strengthening or precipitation strengthening. The effect of improving the high-temperature strength is observed with addition of 0.03% by mass or more. However, since excessive addition leads to hardening of the steel material, the upper limit of each was set to 0.80% by mass for Nb and 0.50% by mass for Ti, Zr, V, and Ta.

[Al: 0.02-0.20 mass%]
In addition to being added as a deoxidizer in the steelmaking stage, it is an optional component that significantly improves high-temperature oxidation resistance by forming an oxide film of Al ₂ O ₃ on the substrate surface. The effect of addition of Al becomes remarkable at 0.02% by mass or more, but excessive addition reduces workability and weldability and impairs the electrical conductivity of the separator, so the upper limit was made 0.20% by mass.

[Y: 0.0005-0.1% by mass, REM: 0.0005-0.1% by mass, Ca: 0.0005-0.01% by mass]
Any of these is an alloy component that is added as necessary, and is dissolved in the oxide film to increase the film strength and further improve the steam oxidation resistance of the ferritic stainless steel. The effects of improving steam oxidation resistance are all significant at 0.0005% by mass or more, but excessive addition hardens the steel material, and surface flaws are likely to occur during production, leading to an increase in production cost. The upper limit of each of Y and REM was 0.1% by mass, and Ca was 0.01% by mass.

[B: 0.0005 to 0.01% by mass]
It is an alloy component that improves the hot workability of stainless steel, and is added as necessary. The effect of improving hot workability becomes significant at 0.0005 mass% or more, but excessive addition deteriorates the hot workability and the surface properties of the steel sheet, so 0.01 mass% was made the upper limit.
[Other ingredients]
The present invention does not particularly define other alloy components, but it is preferable to reduce general impurities such as P, O, and Ni as much as possible. Normally, P is regulated to 0.1% by mass or less, O: 0.02% by mass or less, and Ni: 2.0% by mass or less. However, when a high level of workability and weldability is required. P, O, and Ni are more strictly regulated. Further, Re effective for improving strength, Sn effective for improving free machinability, and elements such as Co, Hf, and Sc effective for improving hot workability, if necessary, Re: 2.0 mass%, Sn: 1.0% by mass, Co: 2.0% by mass, Hf: 1.0% by mass, and Sc: 0.1% by mass can be added to the upper limit.

[TiN coating layer]
The TiN coating layer can be formed by a general method such as sputtering or arc deposition, and a coating layer having good characteristics is produced by any method. In order to sufficiently exhibit the coating effect, the thickness of the TiN coating layer is set to 0.05 μm or more. The thicker the TiN coating layer, the better the characteristics such as steam oxidation resistance and electrical conductivity. However, an excessively thick film causes an increase in manufacturing cost, so the upper limit is set to 100 μm. Preferably, the thickness of the TiN coating layer is adjusted in the range of 0.1 to 10 μm.

  Moreover, by setting the Ti concentration of the coating layer to 40 atomic% or more, good electrical conductivity is maintained in the temperature range of 600 to 800 ° C., and oxidative evaporation of Cr is effectively suppressed. The upper limit of the Ti concentration is not particularly limited, but the upper limit is about 60 atomic% in the method of forming a normal TiN coating layer. In order to provide better electrical conductivity, it is preferable to select a Ti concentration in the range of 47 to 60 atomic%.

  Patent Document 3 discloses that the addition of an oxidizing element to the TiN coating layer is effective in PEFC. However, in the case of SOFC exposed to a high temperature atmosphere of 600 ° C. or higher, the added oxidizing element is electrically An oxide having low conductivity is formed. In particular, when the sum of the V, Zr, and Al concentrations of the coating layer exceeds 10 atomic%, the electrical conductivity is greatly reduced. Therefore, if necessary, the sum of the V, Zr, and Al concentrations of the coating layer is restricted to less than 10 atomic%, and in order to obtain higher electrical conductivity, the sum of the V, Zr, and Al concentrations is set to 2 atomic% or less. It is preferable. Regarding the Cr concentration, when the Cr concentration exceeds 10 atomic%, Cr evaporates in the water vapor atmosphere, and the performance of the solid electrolyte tends to decrease. Therefore, if necessary, the concentration of Cr added to the TiN coating layer is restricted to less than 10 atomic%, and the Cr concentration of the TiN coating layer should be 2 atomic% or less in order to suppress the evaporation of Cr over a longer period. Is preferred.

  Various ferritic stainless steels shown in Table 1 were melted in a 30 kg vacuum melting furnace and cast into ingots. After forging, rough rolling, hot rolling, annealing / pickling, cold rolling, finishing annealing, pickling, a cold rolled annealing / pickling plate with a thickness of 1.5 mm is manufactured, and the hairline finish specified in JIS G4305 did.

A coating layer was formed by sputtering on both surfaces of a stainless steel plate of steel type No. 4 that was hairline finished. In the sputtering method, a stainless steel plate is arranged between a target (cathode) set in a vacuum chamber and an anode plate, the vacuum chamber is evacuated to a high vacuum of 10 ⁻³ Pa or less, and then a vacuum of about 10 ⁻¹ Pa is obtained. Ar gas was introduced so that Then, a voltage of −500 V was applied to the target to generate plasma, and Ar ions accelerated by the voltage were collided with the target. At the same time as sputtering of the target with Ar ions, a mixed gas (reactive gas) of N ₂ or N ₂ and C ₂ H ₂ was introduced into the system to form a coating layer having a predetermined composition on the stainless steel surface. Table 2 shows combinations of target and reaction gas used.

A test piece of 20 mm × 20 mm was cut out from the stainless steel plate on which the coating layer was formed, and the electrical resistance at high temperature was measured.
In the measurement of the high-temperature electric resistance, a platinum electrode for supplying current was attached to each of the solid oxide discs made of yttria-stable zirconia having a radius of 10 mm sandwiching the test piece from both sides. A load was applied to the platinum electrode to adjust the surface pressure of the contact surface between the test piece and the yttria-stable zirconia solid oxide disk to 1.9 kg / cm ² , and the temperature was raised to 750 ° C. in the atmosphere and held for 1000 hours. Thereafter, a constant current of 10 mA was passed between the platinum electrodes, and the potential difference between the yttria-stable zirconia solid oxide disks sandwiching the test piece was measured.
The electrical resistance of the test piece was obtained from the measured value of the potential difference, and converted into electrical resistivity (area resistivity). In separator applications, an electrical resistivity of 30 mΩ · cm ² or less is good, and an electrical resistivity exceeding 30 mΩ · cm ² is evaluated as poor. The measurement results of electrical resistivity are shown in Table 3 together with the composition and thickness of the coating layer.

As can be seen from the test results in Table 3, all of the test pieces formed with coating layers (film symbols A to D) having a Ti concentration of 40 atomic% or more had an electrical resistivity of 30 mΩ · cm ² or less, particularly Ti Concentration: A test piece provided with a coating layer (film symbols A to C) of 47 atomic% or more showed a low electric resistance of less than ²⁰ mΩ · cm ² . The V, Zr, Al concentration and Cr concentration of the TiN coating layer were also low values of 2 atomic% or less in total.

On the other hand, the test pieces provided with other coating layers (film symbols E to H) all have electrical resistivity significantly exceeding 30 mΩ · cm ² , and the required characteristics are not satisfied, making them unsuitable as separator materials. Met. The coating layers E to H contained 10 atomic% or more of V, Zr and / or Al in total. In the coating layer I containing 11 atomic% of Cr, the electrical resistivity was as good as 30 μΩ · cm ² or less, but the Cr evaporation resistance was unsuitable as described later.

After the coating layer was formed on the stainless steel plate of Table 1 by the same sputtering method as in Example 1, it was cut into a 25 mm × 35 mm test piece and subjected to a high temperature steam oxidation test.
In the high temperature steam oxidation test, the test piece was left in an atmosphere of 800 ° C., 50 vol% H ₂ O + 50 vol% air for 300 hours, assuming an atmosphere to which the heat exchanger of the fuel cell is exposed. After 300 hours, the weight of the test piece was measured and compared with the weight before the test. Weight change before and after the test: The steam oxidation resistance of the separator is evaluated with 1 mg / cm ² or less being good (◯) and a weight change exceeding 1 mg / cm ² being poor (x). For some test pieces, the Cr concentration of the coating layer on the surface of the test piece after the steam oxidation test was quantified from the surface layer by WDS (EPMA). In order to correspond to the presence or absence of Cr evaporation, the test piece having a Cr concentration exceeding 10 atomic% was judged as x, and the test piece having 10 atomic% or less was judged as ◯.

  About some test pieces, the presence or absence of Cr evaporation was also investigated. Since Cr evaporates as water-soluble hexavalent chromium in a water vapor atmosphere, all the exhaust gas in the furnace containing water vapor is trapped in 500 ml of water during the test, and the amount of water-soluble chromium contained in the trapped condensed water is After the oxidation test, it was analyzed by spectrophotometry. The Cr evaporation resistance was evaluated with a test piece having a water-soluble chromium content of 0.1 ppm or less as good (◯) and a test piece exceeding 0.1 ppm as poor (×).

As seen in Table 4, all of the test pieces (steel types No. 1 to 11 and film symbols A to D) in which a coating layer of Ti: 40 atomic% or more was provided on stainless steel of Cr: 11 mass% or more. It can be seen that the increase in oxidation is as small as 1 mg / cm ² or less, and it has the necessary characteristics as a solid oxide fuel cell separator material. The amount of Cr eluted from the condensed water was also as low as 0.1 ppm or less, and it was confirmed that it was effective in suppressing chromium poisoning.

On the other hand, in the case of Cr: 11 mass% or more of ferritic stainless steel (steel types No. 4, 11, 12), any test piece that does not form a coating layer has a small oxidation gain of 1 mg / cm ² or less. Water-soluble chromium exceeding 0.1 ppm was detected, and was unsuitable as a solid oxide fuel cell separator material. In addition, in a ferritic stainless steel (steel type Nos. 13 to 15) with Cr: less than 11% by mass, even when a TiN coating layer (film symbol A) with Ti: 40 atomic% or more is applied, the chromium of the base material is insufficient. Therefore, oxidation progressed remarkably, and the increase in oxidation greatly exceeded 1 mg / cm ² , so that it was unsuitable as a solid oxide fuel cell separator material. In the coating layer I having a Cr concentration of 11 atomic%, although the increase in oxidation was small, elution of Cr exceeding 0.1 ppm was detected in the condensed water due to the excessive amount of Cr in the surface layer.
In addition, the display "-" in the column of Cr density | concentration after a steam oxidation test of Table 4, and Cr evaporation resistance shows the test piece which did not analyze surface layer Cr density | concentration or the amount of water-soluble chromium.

  As described above, by forming a TiN coating layer of Ti: 40 atomic% or more on Cr: 11-40 mass% ferritic stainless steel, it exhibits good electrical conductivity and steam oxidation resistance at high temperatures. Since the evaporation of Cr is also suppressed, a separator material suitable for a solid oxide fuel cell can be obtained. The use of the separator material improves the performance and durability of the solid oxide fuel cell without the need for consuming expensive metals such as Ag. Is promoted. Moreover, since the ferritic stainless steel provided with the TiN coating layer is excellent in Cr evaporation resistance, it is not limited to the separator material application and is used in a high-temperature steam atmosphere where Cr evaporation is a concern from the viewpoint of environmental pollution. Expansion into a wide range of fields such as applications that require electrical conductivity at high temperatures is also expected.

Claims (5)

  Cr: 11 to 40% by mass of ferritic stainless steel as a base material, and a TiN coating layer having a film thickness of 0.05 to 100 μm and a Ti concentration of 40 atomic% or more is formed on the surface of the base material. Solid oxide fuel cell separator material.   2. The solid oxide fuel cell separator according to claim 1, wherein the TiN coating layer has a Cr concentration and a V, Zr, and Al concentration of Cr <10 atomic% and V + Zr + Al <10 atomic%.   Base material is Cr: 11-40 mass%, C: 0.1 mass% or less, N: 0.1 mass% or less, Si: 1.5 mass% or less, Mn: 1.5 mass% or less, P: 0 The solid oxide fuel cell separator material according to claim 1 or 2, which is ferritic stainless steel containing not more than .10% by mass and S: not more than 0.01% by mass.   The base material is further Mo: 0.1-4.0% by mass, W: 0.1-4.0% by mass, Nb: 0.05-0.80% by mass, Ti: 0.03-0.50% by mass. %, Cu: 0.1 to 4.0% by mass, Zr: 0.03 to 0.50% by mass, V: 0.03 to 0.50% by mass, Ta: 0.03 to 0.50% by mass, The solid oxide fuel cell separator material according to claim 3, which is a ferritic stainless steel containing one or two or more of Al: 0.02 to 0.20 mass%.   The substrate is further Y: 0.0005-0.1% by mass, REM: 0.0005-0.1% by mass, Ca: 0.0005-0.01% by mass, B: 0.0002-0.01% by mass. 5. The solid oxide fuel cell separator material according to claim 3, which is a ferritic stainless steel containing 1% or 2%.