JP2014037579A - Method for forming heat-shielding coat, and member coated with heat-shielding coat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a heat-shielding coat that is excellent in separation resistance at a high temperature, and to provide a member coated with a heat-shielding coat.SOLUTION: The method for forming a heat-shielding coat includes: forming a bond coat layer comprising an alloy in which Ce is added to an MCrAl or MCrAlY where M is one or more elements selected from Fe, Ni and Co, on the surface of a metal substrate by a cold spray method; forming a top coat layer comprising ceramics on the bond coat layer by atmospheric pressure plasma spraying; and, after forming the top coat layer, growing a wedge-shaped thermally-grown oxide on the bond coat layer with a heat treatment at 1050°C to 1300°C.

Description

  The present invention relates to a method for forming a heat shielding coating and a heat shielding coating-coated member.

  In the initial stage of a gas turbine such as a power plant, the turbine inlet temperature (TIT) was as low as about 800 ° C. and the thermal efficiency was about 30%. However, in recent years, the TIT has reached the 1300 ° C. to 1500 ° C. class, and the thermal efficiency has improved to over 50%. In addition, the use of the combined cycle method enables further improvement in efficiency. Such an increase in TIT has been brought about by advances in cooling technology and improvement of materials in high-temperature parts such as combustors, stationary blades and moving blades. However, since the limit of TIT rise is approaching only by cooling technology and turbine blade material development, it is indispensable to apply a thermal barrier coating (TBC: Thermal Barrier Coating) to the turbine blade. .

  The heat shielding film is a technique for suppressing the temperature rise of the base material by coating the surface of the heat-resistant alloy base material with a ceramic having a low thermal conductivity. Since the turbine rotor blade generally cools the inside, a temperature gradient exists between the surface and the inside. For this reason, by applying a ceramic coating, it is possible to suppress heat conduction and lower the substrate surface temperature.

  A general heat shielding film has a bond coat layer (BC: Bond Coat) made of an MCrAlY alloy (M is one or more elements selected from Fe, Ni, Co) on a Ni-based superalloy substrate. It is formed with a thickness of about 100 μm by low pressure plasma spray (LPPS) or high velocity flame spraying (HVOF), and the yttria stabilized zirconia is formed on the bond coat layer. A top coat layer (TC: Top Coat) made of (YSZ: Yttria Stabilized Zirconia) is applied to atmospheric pressure plasma spray (APS: Air Plasma Spray) or electron beam physical vapor deposition (EB-PVD: Electror). The n Beam-Physical Vapor Deposition), is made to form in a thickness of about 250-300 (e.g., see Non-Patent Document 1 or 2).

  The heat shielding film is expected to be subjected to centrifugal force and vibration due to high-speed rotation, corrosion due to combustion gas, and the like in a high temperature environment. Moreover, since it is exposed to the heat cycle environment accompanying the start / stop of the turbine, there is a risk of peeling or dropping due to aging. When the heat shielding film is peeled off, the substrate is directly exposed to a high temperature environment, which may lead to serious destruction. One factor that governs the degrading degradation of such a thermal barrier coating is the formation of thermally grown oxide (TGO) at the interface between the topcoat layer and the bondcoat layer after prolonged use in a high temperature environment. And growing.

  Therefore, in order to control the generation behavior of the thermally grown oxide and improve the peelability of the heat shielding film, the present inventors have added a trace amount of Ce and Si (0.5 wt%) to the bond coat layer made of CoNiCrAlY. (Ce, 1.0 wt% Si) is added (for example, see Non-Patent Document 3 or Patent Document 1). It has been confirmed that the heat-shielding film has improved peeling resistance due to the wedge-fastening effect of the thermally grown oxide formed so as to be embedded in the bond coat layer.

  Note that when the bond coat layer is formed by LPPS, there is a problem that a thermal effect occurs and a vacuum chamber is required. For this reason, an attempt is made to form a bond coat layer by a cold spray (CS) method in which a film is formed by flying particles at a high speed and greatly deforming the particles (for example, Patent Document 2). Or see 3). Further, it has been reported that the growth rate of the thermally grown oxide is slower in the bond coat layer applied by the cold spray method than in the bond coat layer applied by LPPS (for example, see Non-Patent Document 4). In forming a bond coat layer by a conventional cold spray (CS) method, a CoNiCrAlY alloy is used as a bond coat material. However, materials that can be constructed by LPPS are not necessarily constructable by the CS method. Therefore, when other materials are used, it is necessary to examine the possibility of film formation and the optimum conditions.

Hideyuki Arikawa, Keiyo Kojima, "Heat-resistant coating of gas turbine materials", Surface technology, 2001, Vol.52, No.1, p.11-15 Hideaki Kaneko, Taiji Torigoe, Masahiko Tsumoka, Koji Takahashi, Daisuke Izutsu, `` Technology for improving the reliability of industrial gas turbine thermal barrier coatings '', Journal of the Gas Turbine Society of Japan, 2002, Vol. 30, No. 6, p. 514-518 Toshiki Kato, Kazuhiro Ogawa, Tetsuo Shoko, “Development of thermal barrier coating with excellent peel resistance”, Thermal Spray, 2002, Vol.39, No.2, p.52-57 Atsushi Nakano and Kazuhiro Ogawa, “Influenceof Specimen Shape and Bond Coating Process on Thermally Grown Oxide Growth at the Thermal Barrier Coating / Bond Coating Interface”, Proceedings of ATEM’11,2011, Japan Society of Mechanical Engineers, No.11-203

Japanese Patent No. 3700766 JP 2004-76157 A JP 2011-132565 A

  In recent years, in order to improve thermal efficiency, the turbine inlet temperature (TIT) of gas turbines tends to increase. In order to cope with the next-generation gas turbine that is considered to have a further increase in TIT than the present one, the one having superior peeling resistance at a higher temperature than the heat shielding coating described in Non-Patent Document 3 and Patent Document 1 It is considered necessary.

  The present invention has been made paying attention to such a problem, and an object of the present invention is to provide a method for forming a heat shielding film and a heat shielding film-coated member having excellent peeling resistance at high temperatures.

  The method for forming a heat shielding film according to the present invention is an alloy in which Ce is added to MCrAl or MCrAlY (M is one or more elements selected from Fe, Ni, Co) on the surface of a metal substrate by a cold spray method. A bond coat layer is formed, and a ceramic top coat layer is formed on the bond coat layer, followed by heat treatment at 1050 ° C. to 1300 ° C. to form a wedge-shaped thermally grown oxide on the bond coat layer. It is characterized by growing.

  In the method for forming a heat-shielding film according to the present invention, a bond coat layer is formed by a cold spray method, so that the growth rate of thermally grown oxide (TGO) is slower than that of a bond coat layer formed by LPPS, and peel resistance is improved. It is possible to obtain an excellent heat shielding film. Further, by adding Ce to MCrAl or MCrAlY of the bond coat layer and performing a heat treatment at 1050 ° C. to 1300 ° C., the wedge-shaped TGO can be grown even when the TGO grows inside the bond coat layer. Since the wedge-shaped TGO thus grown causes thermal stress dispersion, it is possible to further improve the peel resistance of the heat shielding film at a high temperature. Note that if the heat treatment temperature exceeds 1300 ° C., melting, structural change or the like occurs, so the heat treatment temperature is set to 1300 ° C. or less.

  Further, in a CoNiCrAlY alloy generally used as a bond coat material, a composite oxide YAG is generated at the interface between the top coat layer and the bond coat layer, and the interface strength is reduced by this oxide. For this reason, when the bond coat layer is made of an alloy obtained by adding Ce to MCrAl, the wedge-shaped TGO grows uniformly and significantly as compared with the case where the bond coat material contains Y, and the top Generation of the composite oxide YAG at the interface between the coat layer and the bond coat layer can be prevented, and the peel resistance of the heat shielding coating can be further improved.

  The heat shielding coating member according to the present invention has a metal substrate and a heat shielding coating formed on the surface of the metal substrate, and the heat shielding coating is MCrAl or MCrAlY (M is Fe, Ni, A bond coat layer formed by a cold spray method made of an alloy obtained by adding Ce to one or more elements selected from Co), and a top coat layer made of ceramics formed on the bond coat layer. A heat treatment is performed at 1050 ° C. to 1300 ° C. to grow a wedge-shaped thermally grown oxide on the bond coat layer.

  The heat shielding film covering member according to the present invention is suitably formed by the method for forming a heat shielding film according to the present invention. Since the heat-shielding coating member according to the present invention has a bond coat layer formed by a cold spray method, the heat-shielding coating has excellent peel resistance. Further, since Ce is added to MCrAl or MCrAlY of the bond coat layer and heat treatment is performed at 1050 ° C. to 1300 ° C., the peel resistance at a high temperature of the heat shielding coating can be further improved. Further, when the bond coat layer is made of an alloy obtained by adding Ce to MCrAl, the wedge-shaped TGO is uniformly and significantly grown as compared with the case where the bond coat material contains Y, It is possible to prevent the composite oxide YAG from being generated at the interface between the top coat layer and the bond coat layer, and to further improve the peel resistance of the heat shielding coating.

  ADVANTAGE OF THE INVENTION According to this invention, the formation method and heat shielding film coating | coated member of the heat shielding film excellent in the peeling resistance in high temperature can be provided.

(A) The heat shielding coating member of the embodiment using CoNiCrAl + Ce as the bond coat material, (b) CoNiCrAlY + Ce, (c) The top of the comparative example using CoNiCrAlY as the bond coat material at a heat treatment time of 1000 hours It is a scanning electron microscope (SEM) image of the interface (TC / BC interface) of a coat layer and a bond coat layer. It is a SEM image of the TC / BC interface in heat processing time (a) 0 hours and (b) 1000 hours of the heat shielding film covering member of the embodiment of the present invention using CoNiCrAl + Ce as a bond coat material. An SEM image of a TC / BC interface at a heat treatment time of 1000 hours and an EDX element mapping of four kinds of elements in the image region of the heat shielding coating member according to the embodiment of the present invention using CoNiCrAl + Ce as a bond coat material It is. SEM image of TC / BC interface with heat treatment time of 1000 hours and EDX element mapping of four kinds of elements in the image area of the heat shielding coating coated member of the embodiment of the present invention using CoNiCrAlY + Ce as the bond coat material It is. A SEM image of a TC / BC interface with a heat treatment time of 300 hours, and four kinds of elements in the image region, as a comparative example for the heat shielding coating member according to the embodiment of the present invention using CoNiCrAlY as a bond coat material This is an EDX element mapping. It is a side view which shows the general view of the four-point bending test method with respect to the heat shielding film coating | coated member of embodiment of this invention, and a comparative example. It is a graph which shows the four-point bending test result after the heat aging treatment for 100 hours in 1100 degreeC atmospheric environment of the heat shielding film coating | coated member of embodiment of this invention, and a comparative example. (A) Heat shielding film covering member according to the embodiment of the present invention using (b) CoNiCrAlY + Ce as a bond coat material, (c) Comparative example using CoNiCrAlY as a bond coat material in an atmospheric environment at 1100 ° C. It is a SEM image in the peeling point after the four-point bending test after 100-hour thermal aging treatment.

Embodiments of the present invention will be described below.
The heat shielding coating member according to the embodiment of the present invention is formed as follows by the method for forming a heat shielding coating according to the embodiment of the present invention. That is, first, a bond coat layer made of an alloy in which Ce is added to MCrAl or MCrAlY (M is one or more elements selected from Fe, Ni, Co) by a cold spray method on the surface of a metal substrate. It is formed with a thickness of about 100 μm. The metal substrate is, for example, a heat resistant alloy Ni-base superalloy. The bond coat material is, for example, a CoNiCrAl + Ce alloy or a CoNiCrAlY + Ce alloy.

  Next, a top coat layer made of ceramic is formed to a thickness of 250 to 300 μm on the bond coat layer by atmospheric pressure plasma spraying (APS). The topcoat layer is, for example, yttria stabilized zirconia (YSZ). After forming the topcoat layer, heat treatment is performed at about 1100 ° C. In this way, the heat shielding film covering member of the embodiment of the present invention can be formed.

  In the method for forming a heat shielding film according to the embodiment of the present invention, since the bond coat layer is formed by a cold spray method, the growth rate of TGO (thermally grown oxide) is slower than the bond coat layer formed by LPPS, A heat shielding film having excellent peeling resistance can be obtained. Further, when Ce is added to MCrAl or MCrAlY of the bond coat layer and heat treatment is performed at about 1100 ° C., wedge-shaped TGO can be grown even when TGO grows inside the bond coat layer. Since the wedge-shaped TGO thus grown causes thermal stress dispersion, it is possible to further improve the peel resistance of the heat shielding film at a high temperature.

  Further, when the bond coat layer is made of an alloy obtained by adding Ce to MCrAl, the wedge-shaped TGO is uniformly and significantly grown as compared with the case where the bond coat material contains Y, It is possible to prevent the composite oxide YAG from being generated at the interface between the top coat layer and the bond coat layer, and to further improve the peel resistance of the heat shielding coating.

  A bond coat layer having a thickness of about 100 μm was formed on the surface of the metal substrate by a cold spray method, and a top coat layer having a thickness of about 300 μm was formed on the bond coat layer by APS. As the metal substrate, a 3 mm thick polycrystalline Ni-base superalloy (Inconel 738LC) was used. CoNiCrAl + Ce (hereinafter “Example 1”) and CoNiCrAlY + Ce (hereinafter “Example 2”) were used as bond coat materials. For comparison, a material using CoNiCrAlY (“AMDRY 9951” manufactured by SULZER METCO) (hereinafter “Comparative Example”) was also formed as a bond coat material. The chemical composition of each bond coat material is shown in Table 1. As the top coat material, 8 wt% YSZ (“METCO 204NS” manufactured by SULZER METCO) was used.

  Using the formed heat-shielding coating member of each bond coat material, observation of the formation state of TGO (thermally grown oxide) and a four-point bending test were performed.

[Observation of TGO generation state]
The heat shielding film covering member using each bond coat material was cut into 10 mm in length, 10 mm in width, and 3 mm in thickness by machining, and subjected to heat aging treatment. The thermal aging treatment was performed at 1000 ° C. in an atmospheric environment in a high temperature electric furnace (“FO401” manufactured by Yamato Scientific). The interface (TC / BC interface) between the top coat layer and the bond coat layer after the thermal aging treatment was observed with a scanning electron microscope (SEM), and the generation state of TGO in each bond coat material was evaluated. . For SEM observation, a field emission scanning electron microscope (“FE-SEM S-4700” manufactured by HITACHI) was used.

  Moreover, in order to identify the oxide which comprises TGO (thermally grown oxide), the qualitative elemental analysis was performed with the energy dispersive X-ray spectrometer (EDX). For the EDX analysis, an EDX analyzer (manufactured by EDAX) mounted on a field emission scanning electron microscope (“FE-SEM S-4700”) was used.

  FIG. 1 shows an SEM image of the TC / BC interface of each bond coat material at a heat treatment time of 1000 hours. Moreover, the SEM image of the TC / BC interface in the heat treatment time of 0 hour and 1000 hours of CoNiCrAl + Ce of Example 1 is shown in FIG. Furthermore, the EDX element mapping by the EDX analysis at the heat treatment time of 1000 hours or 300 hours for each bond coat material is shown in FIGS. 3 to 5, respectively. In any of FIGS. 1 to 5, the upper side in the figure is a top coat (TC) layer, and the lower side is a bond coat (BC) layer.

  In CoNiCrAl + Ce of Example 1 and CoNiCrAlY + Ce of Example 2, as shown in FIGS. 1A, 1B, and 2, as the heat treatment time proceeds, wedge-shaped TGO grows so as to disperse inside the bond coat layer. I was able to confirm. This is presumably because Ce oxide becomes a diffusion path, oxygen penetrates into the bond coat layer, and the wedge-shaped TGO grows. Since this wedge-shaped TGO causes thermal stress dispersion, it is considered that the peel resistance of the heat shielding coating is improved.

  In addition, CoNiCrAl + Ce and CoNiCrAlY + Ce were different in the growth of wedge-shaped TGO, and it was confirmed that CoNiCrAl + Ce was growing significantly. Further, TGO grew at any location in CoNiCrAl + Ce, but it was confirmed that CoNiCrAlY + Ce had different wedge-shaped TGO growth rates depending on the location. These differences are thought to be due to the presence or absence of Y. Due to the difference in growth of the wedge-shaped TGO, CoNiCrAl + Ce is considered to have higher peeling resistance than CoNiCrAlY + Ce.

  On the other hand, in the CoNiCrAlY of the comparative example which is a conventional material, as shown in FIG. 1C, it was confirmed that a thin TGO grew at the TC / BC interface as the heat treatment time increased. Further, as shown in FIG. 3, it was confirmed that the grown TGO had a substantially uniform thickness regardless of the location.

In CoNiCrAl + Ce of Example 1 and CoNiCrAlY + Ce of Example 2, as shown in FIG. 3 and FIG. 4, white points considered to be CeO ₂ of Ce oxide in the bond coat layer at the initial stage of heat treatment. It was confirmed that the existence existed. In addition, the presence of Cr oxide was observed in the TGO, but no oxide was confirmed in the upper part of the TGO. On the other hand, in CoNiCrAlY which does not contain Ce of the comparative example, as shown in FIG. 5, TGO is considered to be an Al oxide. In addition, the presence of a mixed oxide layer in which oxides of Co, Ni, and Cr were mixed was confirmed on the TGO.

[Four-point bending test]
The heat-shielding coating member using each bond coat material was cut into a length of 50 mm, a width of 5 mm, and a thickness of 3.4 mm by machining, and the atmospheric environment at 1000 ° C. for 500 hours and the atmospheric environment at 1100 ° C. Under the heat aging treatment of 100 hours under. A four-point bending test was performed by the method shown in FIG. 6 using each test piece after the heat aging treatment. A material fatigue tester (“810 Material Test System” manufactured by MTS) was used for the four-point bending test. The distance between the fulcrum points of the jigs on both sides of the test piece was set to 34 mm and 15 mm, respectively, and the tensile stress was set to act on the heat shielding coating side. The displacement speed of the jig on the metal substrate side was made constant at 0.01 mm / sec, and a load was applied until peeling was confirmed.

  A strain gauge (“KFG-2N-120-C1-11L1M2R” manufactured by Kyowa Dengyo) is attached to the surface of the test piece on the metal substrate side, and acoustic emission (AE) is applied to the side surface of one jig on the heat shielding coating side. : Acoustic Emission) sensor was attached, and the compressive strain and AE signal on the surface of the metal substrate were measured. For the measurement of AE, an AE workstation (“DiSP AE Workstation” manufactured by PHYSICAL ACOUSTIC) was used.

  Here, when peeling of the heat shielding film occurs in the four-point bending test, the cumulative AE count obtained by sequentially accumulating the AE counts rapidly rises. Therefore, the sudden rise point of the cumulative AE count is defined as the peeling occurrence point. By measuring the amount of compressive strain on the surface of the metal substrate at the separation occurrence point, it is possible to quantitatively evaluate the separation resistance when a tensile load acts on the heat shielding coating.

  FIG. 7 shows the results of a four-point bending test after thermal aging treatment for 100 hours in an air environment at 1100 ° C. Moreover, the SEM image of the peeling point after a four-point bending test is shown in FIG.

  When thermal aging treatment is performed for 100 hours in an atmospheric environment at 1100 ° C., as shown in FIG. 7, the CoNiCrAl + Ce of Example 1 has the best peeling resistance, and the peeling resistance of the CoNiCrAlY of the comparative example is The lowest was confirmed. As shown in FIG. 8A, it was confirmed that CoNiCrAl + Ce had a wedge-shaped TGO uniformly grown at the peeling position, and this was considered to have improved peeling resistance. Moreover, as shown in FIG.8 (b), it was confirmed that the wedge-shaped TGO has grown partially about CoNiCrAlY + Ce of Example 2. FIG. From this, it is considered that CoNiCrAlY + Ce has a peeling resistance higher than that of the comparative example CoNiCrAlY and lower than that of CoNiCrAl + Ce. Moreover, as shown in FIG.8 (c), it is confirmed that CoNiCrAlY of a comparative example has peeled from the upper part of TGO, and it is thought that the mixed oxide layer is a starting point of peeling.

From the above results, considering the next-generation gas turbine that is considered to increase the TIT (turbine inlet temperature), the bond coat material has the highest peel resistance when subjected to thermal aging treatment at 1100 ° C. The obtained CoNiCrAl + Ce is the most effective and is slightly inferior to the peel resistance, but CoNiCrAlY + Ce is also considered effective. In addition, it is considered that the strength at a high temperature of the heat shielding film can be increased by performing heat treatment at 1100 ° C. in advance on the heat shielding film using CoNiCrAl + Ce or CoNiCrAlY + Ce as the bond coat material.

Claims (2)

  A bond coat layer made of an alloy obtained by adding Ce to MCrAl or MCrAlY (M is one or more elements selected from Fe, Ni, Co) is formed on the surface of the metal substrate by a cold spray method, Forming a top coat layer made of ceramics on the layer and then performing a heat treatment at 1050 ° C. to 1300 ° C. to grow a wedge-shaped thermally grown oxide on the bond coat layer; Method. A metal substrate and a heat shielding film formed on the surface of the metal substrate;
The heat shielding film includes a bond coat layer formed by a cold spray method made of an alloy obtained by adding Ce to MCrAl or MCrAlY (M is one or more elements selected from Fe, Ni, Co), and the bond coat And a top coat layer made of ceramics formed on the layer, and heat-treated at 1050 ° C. to 1300 ° C. to grow a wedge-shaped thermally grown oxide on the bond coat layer. Film covering member.