Surface alloy coating composite material used for high temperature resistant material, coating and preparation method thereof

Abstract

The present invention provides a surface alloy coating composite material for a high temperature resistant material, a coating and a manufacturing method thereof, wherein the surface alloy coating composite material is made of metal alloy powder having a face-centered cubic structure and enamel powder, and a component percentage thereof is as follows: 10-70 wt % is the metal alloy powder, and remaining is the enamel powder; the metal alloy powder is selected from at least one type of NiCrAIX, NiCrX and NiCoCrAIX, wherein X is at least one type of hafnium, zirconium, a rare earth element and mixed rare earth, and the mixed rare earth can be two types or more than two types of rare earth elements that are used together or a rare earth element and one type or multiple types of Na, K, Ca, Sr and Ba that are used in a combined way.

Claims

1. A method for manufacturing a coating, wherein the coating is made of a surface alloy coating composite material, wherein the surface alloy coating composite material is used for a thermal resistant material, wherein the surface alloy coating composite material is made of metal alloy powder with a face-centered cubic structure and enamel powder, and a component percentage thereof is as follows: 10-70 wt % is the metal alloy powder, and the remaining is the enamel powder; the metal alloy powder is at least one type selected from the group consisting of NiCrAIX, NiCrX and NiCoCrAIX, wherein the diameter of the metal alloy powder is 0.1 m-15 m, wherein X is at least one type of hafnium, zirconium, a rare earth element and mixed rare earth, and the mixed rare earth is two types or more than two types of rare earth elements that are used together, or a rare earth element and one type or multiple types of Na, K, Ca, Sr and Ba that are used in a combined way; the surface alloy coating composite material contains: 10 wt %40 wt % Cr, 0-30 wt % Al, 0.1 wt %5 wt % X, and the total amount of Cr, Al and X are 25 wt %45 wt %, wherein the amount of Co is no more than the amount of Ni, wherein the metal alloy powder or the metal alloy powder and a hardness-reinforcing phase are uniformly distributed in a base matrix made of the enamel powder to define a metal alloy-enamel coating, a metal alloy-enamel-hardness-reinforcing phase coating or a composite coating comprising a metal alloy-enamel coating and a metal alloy-enamel-hardness-reinforcing phase coating provided on the surface of an alloy, wherein the softening temperature of the base matrix made of the enamel powder is 600 C.-900 C., wherein the coefficient of thermal extension of the surface alloy coating composite material is 7.010.sup.6K.sup.-12.010.sup.6K.sup.1, wherein the method for manufacturing the coating comprises the steps of: (A) mixing evenly the metal alloy powder and the enamel powder; (B) spray-coating the mixed powder on the surface of a component made of a material; and (C) treating the sprayed component made of the material under high temperature to form a thermal protection coating on the surface of the component, wherein the thermal protection coating is dense, smooth and continuous, wherein in the thermal protection coating, the metal alloy powder with a face-centered cubic structure is uniformly distributed in a substrate made of the enamel powder such that an interfacial reaction is capable of being processed between the metal alloy powder and the surface of the substrate to form a metallurgic bonding there between, wherein in the step (C), the treating of the sprayed component made of the material under high temperature employs a heating method with variable heating rates: firstly, elevating the temperature up to 150 C.-250 C. by 3 C./min and then keeping the coated component under 150 C.-250 C. for 2 h-4 h so as to dehydrate the coating; secondly, elevating the temperature up to 800 C.-1100 C. by at least 20 C./min so as to avoid the crystallization temperature of the enamel and then keeping the coated component under 800 C.-1100 C. for 10 min-60 min; lastly, taking the component out of the heating furnace and cooling the component in still ambient air to room temperature.

2. A method for manufacturing a coating, wherein the coating is made of a surface alloy coating composite material, wherein the surface alloy coating composite material is used for a thermal resistant material, wherein the surface alloy coating composite material is made of metal alloy powder with a face-centered cubic structure and enamel powder, and a component percentage thereof is as follows: 10-70 wt % is the metal alloy powder, and the remaining is the enamel powder; the metal alloy powder is at least one type selected from the group consisting of NiCrAIX, NiCrX and NiCoCrAIX, wherein the diameter of the metal alloy powder is 0.1 m-15 m, wherein X is at least one type of hafnium, zirconium, a rare earth element and mixed rare earth, and the mixed rare earth is two types or more than two types of rare earth elements that are used together, or a rare earth element and one type or multiple types of Na, K, Ca, Sr and Ba that are used in a combined way; the surface alloy coating composite material contains: 10 wt %40 wt % Cr, 0-30 wt % Al, 0.1 wt %5 wt % X, and the total amount of Cr, Al and X are 25 wt %45 wt %, wherein the amount of Co is no more than the amount of Ni, wherein the metal alloy powder or the metal alloy powder and a hardness-reinforcing phase are uniformly distributed in a base matrix made of the enamel powder to define a metal alloy-enamel coating, a metal alloy-enamel-hardness-reinforcing phase coating or a composite coating comprising a metal alloy-enamel coating and a metal alloy-enamel-hardness-reinforcing phase coating provided on the surface of an alloy, wherein the softening temperature of the base matrix made of the enamel powder is 600 C.-900 C., wherein the coefficient of thermal extension of the surface alloy coating composite material is 7.010.sup.6K.sup.-12.010.sup.6K.sup.1, wherein the method for manufacturing the coating comprises the steps of: (A) mixing evenly the metal alloy powder and the enamel powder; (B) spray-coating the mixed powder on the surface of a component made of a material; and (C) treating the sprayed component made of the material under high temperature to form a thermal protection coating on the surface of the component, wherein the thermal protection coating is dense, smooth and continuous, wherein in the thermal protection coating, the metal alloy powder with a face-centered cubic structure is uniformly distributed in a substrate made of the enamel powder such that an interfacial reaction is capable of being processed between the metal alloy powder and the surface of the substrate to form a metallurgic bonding there between, wherein the component is pre-oxidized for 5 min-60 min under 600 C.-1000 C. in advance to form an oxide film on the surface of the component, before the mixed powder is sprayed on the surface of the component, wherein the thickness of the oxide film is 0.2 m-2 m.

3. A method for manufacturing the coating, wherein the coating is made of a surface alloy coating composite material, wherein the surface alloy coating composite material is used for a thermal resistant material, wherein the surface alloy coating composite material is made of metal alloy powder with a face-centered cubic structure and enamel powder, and a component percentage thereof is as follows: 10-70 wt % is the metal alloy powder, and the remaining is the enamel powder; the metal alloy powder is at least one type selected from the group consisting of NiCrAIX, NiCrX and NiCoCrAIX, wherein the diameter of the metal alloy powder is 0.1 m-15 m, wherein X is at least one type of hafnium, zirconium, a rare earth element and mixed rare earth, and the mixed rare earth is two types or more than two types of rare earth elements that are used together, or a rare earth element and one type or multiple types of Na, K, Ca, Sr and Ba that are used in a combined way; the surface alloy coating composite material contains: 10 wt %40 wt % Cr, 0-30 wt % Al, 0.1 wt %5 wt % X, and the total amount of Cr, Al and X are 25 wt %45 wt %, wherein the amount of Co is no more than the amount of Ni, wherein the face-centered cubic structure phase is partially replaced by a hardness-reinforcing phase, wherein the metal alloy powder is partially substituted by least one compound selected from the group consisting of alumina, quartz, ZrO.sub.2, Cr.sub.2O.sub.3, AlN, Si.sub.3N.sub.4, BN and SiC, wherein the amount of the substituted compound is no more than 30 wt %, wherein the metal alloy powder or the metal alloy powder and a hardness-reinforcing phase are uniformly distributed in a base matrix made of the enamel powder to define a metal alloy-enamel coating, a metal alloy-enamel-hardness-reinforcing phase coating or a composite coating comprising a metal alloy-enamel coating and a metal alloy-enamel-hardness-reinforcing phase coating provided on the surface of an alloy, wherein the softening temperature of the base matrix made of the enamel powder is 600 C.-900 C., wherein the coefficient of thermal extension of the surface alloy coating composite material is 7.010.sup.6K.sup.1-12.010.sup.6K.sup.1, wherein the method of manufacturing the coating comprises the steps of: (A) mixing evenly the metal alloy powder and the enamel powder; (B) spray-coating the mixed powder on the surface of a component made of a material; and (C) treating the sprayed component made of the material under high temperature to form a thermal protection coating on the surface of the component, wherein the thermal protection coating is dense, smooth and continuous, wherein in the thermal protection coating, the metal alloy powder with a face-centered cubic structure is uniformly distributed in a substrate made of the enamel powder such that an interfacial reaction is capable of being processed between the metal alloy powder and the surface of the substrate to form a metallurgic bonding therebetween, wherein in the step (C), the treating of the sprayed component made of the material under high temperature employs a heating method with variable heating rates: firstly, elevating the temperature up to 150 C.-250 C. by 3 C./min and then keeping the coated component under 150 C.-250 C. for 2 h-4 h so as to dehydrate the coating; secondly, elevating the temperature up to 800 C.-1100 C. by at least 20 C./min so as to avoid the crystallization temperature of the enamel and then keeping the coated component under 800 C.-1100 C. for 10 min-60 min; lastly, taking the component out of the heating furnace and cooling the component in still ambient air to room temperature.

4. A method for manufacturing the coating, wherein the coating is made of a surface alloy coating composite material, wherein the surface alloy coating composite material is used for a thermal resistant material, wherein the surface alloy coating composite material is made of metal alloy powder with a face-centered cubic structure and enamel powder, and a component percentage thereof is as follows: 10-70 wt % is the metal alloy powder, and the remaining is the enamel powder; the metal alloy powder is at least one type selected from the group consisting of NiCrAIX, NiCrX and NiCoCrAIX, wherein the diameter of the metal alloy powder is 0.1 m-15 m, wherein X is at least one type of hafnium, zirconium, a rare earth element and mixed rare earth, and the mixed rare earth is two types or more than two types of rare earth elements that are used together, or a rare earth element and one type or multiple types of Na, K, Ca, Sr and Ba that are used in a combined way; the surface alloy coating composite material contains: 10 wt %40 wt % Cr, 0-30 wt % Al, 0.1 wt %5 wt % X, and the total amount of Cr, Al and X are 25 wt %45 wt %, wherein the amount of Co is no more than the amount of Ni, wherein the face-centered cubic structure phase is partially replaced by a hardness-reinforcing phase, wherein the metal alloy powder is partially substituted by least one compound selected from the group consisting of alumina, quartz, ZrO.sub.2, Cr.sub.2O.sub.3, AlN, Si.sub.3N.sub.4, BN and SiC, wherein the amount of the substituted compound is no more than 30 wt %, wherein the metal alloy powder or the metal alloy powder and a hardness-reinforcing phase are uniformly distributed in a base matrix made of the enamel powder to define a metal alloy-enamel coating, a metal alloy-enamel-hardness-reinforcing phase coating or a composite coating comprising a metal alloy-enamel coating and a metal alloy-enamel-hardness-reinforcing phase coating provided on the surface of an alloy, wherein the softening temperature of the base matrix made of the enamel powder is 600 C.-900 C., wherein the coefficient of thermal extension of the surface alloy coating composite material is 7.010.sup.6K.sup.1-12.010.sup.6K.sup.1, wherein the method of manufacturing the coating comprises the steps of: (A) mixing evenly the metal alloy powder and the enamel powder; (B) spray-coating the mixed powder on the surface of a component made of a material; and (C) treating the sprayed component made of the material under high temperature to form a thermal protection coating on the surface of the component, wherein the thermal protection coating is dense, smooth and continuous, wherein in the thermal protection coating, the metal alloy powder with a face-centered cubic structure is uniformly distributed in a substrate made of the enamel powder such that an interfacial reaction is capable of being processed between the metal alloy powder and the surface of the substrate to form a metallurgic bonding therebetween, wherein the component is pre-oxidized for 5 min-60 min under 600 C.-1000 C. in advance to form an oxide film on the surface of the component, before the mixed powder is sprayed on the surface of the component, wherein the thickness of the oxide film is 0.2 m-2 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a XRD pattern of the coating having a 30 wt % metal alloy fracture toughness enhancement phase and 70 wt % enamel, wherein the coating is under an as-prepared state, wherein a-phase is -Ni/-Ni.sub.3Al, and b phase is NiCr.sub.2O.sub.4.

(2) FIG. 2 is a XRD pattern of the coating having a 10 wt % metal alloy fracture toughness enhancement phase, 70 wt % enamel and 20 wt % alumina, wherein the coatings are respectively under as-prepared state and after hot shocking at 1000 C., wherein a: /, b: -Al.sub.2O.sub.3, c: ZnAl.sub.2O.sub.4, d: Na(AlSi.sub.3O.sub.8), e: K(AlSi.sub.3O.sub.8), f: t-ZrO.sub.2, g: NiCr.sub.2O.sub.4/ZnCr.sub.2O.sub.4.

(3) FIG. 3 shows the shock resistance of the enamel-NiCrLa material (indentation-water quenching method), wherein PE, E10M, E20M, E30M respectively represent the material containing 0, 10, 20, 30 wt % metal alloy particles.

(4) FIG. 4 shows hot-shock weight loss curves of several enamel-metal materials. E20A and E30A are respectively the materials containing 20 and 30 wt % alumina hardness enhancement phase, and E20A10M is a material containing 20 wt % alumina hardness enhancement phase and 10 wt % metal alloy fracture toughness enhancement phase.

(5) FIG. 5 shows thermal expansion curves of pure enamel material and enamel-alumina-metal alloy material, wherein E20A10M is a material containing 20 wt % alumina hardness enhancement phase and 10 wt % metal alloy fracture toughness enhancement phase.

(6) FIG. 6 shows 1000 C. cyclic oxidation curves of alumina-enamel coating and metal alloy-enamel-alumina coating; wherein E30A is a material containing 30 wt % alumina hardness enhancement phase, E20A10M is a material containing 20 wt % alumina hardness enhancement phase and 10 wt % metal alloy fracture toughness enhancement phase.

(7) FIG. 7 shows thermal expansion coefficient curves of various enamel-metal alloy materials, wherein P, E5M, E10M, E15M, E20M, E25M and E30M respectively illustrate that the material contains 0, 5, 10, 15, 20, 25, 30 wt % metal alloy fracture toughness enhancement phase.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Example 1

(8) Ball-milling enamel material for 100 h in an agate jar to preparing the enamel powder, wherein the diameter of the enamel powder (particles) is no more than 5 m. Mixing 140 g enamel powder with 60 g Ni-25Cr-5Al-1Zr-0.5La (wt %) alloy powder, wherein the diameter of the Ni-25Cr-5Al-1Zr-0.5La (wt %) alloy powder (particles) is less than 40 m, dry-milling for 10 h. Compression moulding the mixed powder for 20 min into powder block under 15 MPa, and then taking the powder block out of the mold, baking the powder block for 2 h at 250 C. to remove moisture. Raising the temperature in 3 C./min, until the temperature is raised up to 590 C. and then raising the temperature in 20 C./min, when the temperature is over the temperature range 800 C.-850 C., setting the sintering temperature at 950 C., and then keeping the temperature at 950 C. for 30 min, and then cooling the powder block in the furnace to room temperature so as to get a face-centered cubic high temperature metal alloy-enamel surface alloy coating composite material.

(9) By the XRD diffraction proof, it is proved that in the coating, the metal alloy is -Ni/-Ni.sub.3Al, which has a face-centered cubic structure, as shown in FIG. 1. A number of physical properties of the composite material is improved, wherein the thermal expansion coefficient of the composite material is 7.010.sup.6K.sup.1/ C., the fracture toughness of the composite material is 2.0 MPa.Math.m.sup.1/2, the Young's modulus is 81.1 GPa. In contrast, the thermal expansion coefficient of the pure thermal expansion powder is only 5.710.sup.6K.sup.1/ C., the fracture toughness is only 1.0 MPa.Math.m.sup.1/2, the Young's modulus is only 72 GPa. All of this shows that each of the composite material and the corresponding coating has excellent thermal shock resistance, not only because improving of the thermal expansion coefficient reduces the thermal stress force, but the fracture toughness and the Young's modulus are significantly improved also play an important role by improving the material crack initiation and the expansion stress.

Example 2

(10) Ball-milling enamel material for 100 h in an agate jar to preparing the enamel powder, wherein the diameter of the enamel powder (particles) is no more than 5 m. Mixing 100 g enamel powder with 40 g Ni-25Cr-5Al-1Zr-0.5La (wt %) alloy powder and 60 g alumina powder, wherein the diameter of the Ni-25Cr-5Al-1Zr-0.5La (wt %) alloy powder (particles) is less than 40 m, the diameter of the alumina powder (particles) is about 7 m, dry-milling for 10 h. Compression moulding the mixed powder for 20 min into powder block under 15 MPa, and then taking the powder block out of the mold, baking the powder block for 2 h at 250 C. to remove moisture. Raising the temperature in 3 C./min, until the temperature is raised up to 590 C. and then raising the temperature in 20 C./min, when the temperature is over the temperature range 800 C.-850 C., setting the sintering temperature at 950 C., and then keeping the temperature at 950 C. for 30 min, and then cooling the powder block in the furnace to room temperature so as to get a face-centered cubic high temperature metal alloy-enamel-hardness enhancement phase surface alloy coating composite material.

(11) By the XRD diffraction proof, it is proved that in the coating, the metal alloy is -Ni/-Ni.sub.3Al, which has a face-centered cubic structure, and the coating material further contains -Al.sub.2O.sub.3 as the hardness enhancement phase thereof, wherein the coating material may further contain ZnAl.sub.2O.sub.4, Na(AlSi.sub.3O.sub.8), K(AlSi.sub.3O.sub.8), t-ZrO.sub.2 and NiCr.sub.2O.sub.4 and ZnCr.sub.2O.sub.4 as a reaction phases thereof, which are respectively the hardness enhancement phase, as shown in FIG. 2. The composite material has no crack when is under 1000 C. hot shock condition, which has excellent thermal shock resistance, and after the composite material is treated in the experiment, it still has the above metal alloy phase and the hardness enhancement phase and has excellent structural stability.

Example 3

(12) Ball-milling enamel material for 100 h in an agate jar to preparing the enamel powder, wherein the diameter of the enamel powder (particles) is no more than 5 m. Preparing respectively 200 g enamel powder, 180 g enamel powder and 20 g Ni-25Cr-5Al-1Zr-0.5La (wt %) alloy powder, 160 g enamel powder and 40 g Ni-25Cr-5Al-1Zr-0.5La (wt %) alloy powder, 140 g enamel powder and 60 g Ni-25Cr-5Al-1Zr-0.5La (wt %) alloy powder, wherein the diameter of the Ni-25Cr-5Al-1Zr-0.5La (wt %) alloy powder (particles) is less than 40 m. Mixing and Dry-milling respectively for 10 h. Compression moulding respectively the mixed powders for 20 min into powder blocks under 15 MPa, and then taking the powder blocks out of the mold, baking the powder blocks for 2 h at 250 C. to remove moisture. Raising the temperature in 3 C./min, until the temperature is raised up to 590 C. and then raising the temperature in 20 C./min, when the temperature is over the temperature range 800 C.-850 C., setting the sintering temperature at 950 C., and then keeping the temperature at 950 C. for 30 min, and then cooling the powder block in the furnace to room temperature so as to get a pure enamel material and three face-centered cubic high temperature metal alloy-enamel composite material.

(13) Testing the samples by the indentation-water quenching test (as shown in FIG. 3), that is, which uses micro-hardness diamond to indenter in the polished surfaces of the samples to prefabricate 1 m-4 m micro-cracks therein, then heating the samples up to the test temperature, thermal insulating for 30 min, rapid cooling in deionized water at 25 C., observing crack propagation. The test results of the indentation-water quenching test show that the crack growth curve moves to the right following the improvement of the content of the face-centered cubic metal alloy particles in the material, that is, with the alloy particles content is increased, the toughness of the material is significantly enhanced. When the content of the metal phase reaches 30 wt %, the crack don't increase infinitely with the raised temperature difference of insulating temperature-water quenching temperature while stop extending when the crack grows a maximum size of 10 m. After the hot shock tests are accomplished, the mechanism of crack deflection, crack bridging and alloys-enamel interface cracking, all of this shows that the face-centered cubic nickel-based alloy particles having high toughness have good wettability and binding force with the enamel base matrix thereof, because of its rare earth-containing, which plays an important role in improving the thermal shock resistance.

Example 4

(14) Ball-milling enamel material for 100 h in an agate jar to preparing the enamel powder, wherein the diameter of the enamel powder (particles) is no more than 5 m. Preparing respectively 160 g enamel powder and 40 g Ni-25Cr-5Al-1Zr-0.5La (wt %) alloy powder, 140 g enamel powder and 60 g Ni-25Cr-5Al-1Zr-0.5La (wt %) alloy powder, 140 g enamel powder, 20 g Ni-25Cr-5Al-1Zr-0.5La (wt %) alloy powder and 40 g alumina powder, wherein the diameter of the alumina powder (particles) is about 7 m. Dry-milling each powder mixture for 10 h. Preparing slurries by adding ethyl alcohol into the above-prepared three types of powder mixtures. Selecting the nickel-based high temperature alloy K38G as the substrate, wherein the chemical compositions are as shown in Table 1 and the thermal expansion coefficient is 1810.sup.6K.sup.1.

(15) Pre-oxidizing the component for 5 min at 850 C. to form a thin oxide film on the surface of the component before the slurries are sprayed on the substrates, wherein the oxide film is amorphous to be in favor of combining with the amorphous enamel. Preparing the three mixed powders with ethyl alcohol into slurries, and making the powders be distributed uniformly only by ultrasonic vibration, without any dispersing agent; at room temperature atmosphere, spraying the slurries on the sheet components made of high-temperature alloy K38G, wherein the size of the sheet component is 100 mm20 mm2 mm, then baking the components for 15 min at 250 C., and finally treating for 10 min at 950 C. to form a coating having a thickness of about 30 m. Each cycle of the thermal shocking test is performed by heating the components for 30 min at 1000 C. and then quenching the components into deionized water. The test results of quality change curves of the components is shown in FIG. 4, which shows that the coatings, especially the coating made of alloy-enamel-aluminum oxide material, has excellent thermal shock resistance without any peeling. The peeling situations of the other coatings are also much better than the pure enamel coating. 50% of the pure enamel coating surface is peeled off just under the as-prepared status, and the remaining of the coating is completely peeled off after only 1 cycle of thermal shocking test.

(16) TABLE-US-00001 TABLE 1 Chemical compositions of high temperature alloy K38G (wt %) Ni C Cr Al Co W B Ti Mo Nb Ta P Bal. 0.17 16.0 4.0 8.5 2.0 0.01 3.8 1.7 0.7 1.7 <0.01

Example 5

(17) Preparing respectively 180 g enamel powder, 20 g Ni-25Cr-5Al-1Zr-0.5La (wt %) alloy powder and 60 g alumina powder, wherein the diameter of the Ni-25Cr-5Al-1Zr-0.5La (wt %) alloy powder (particles) is less than 40 m, the diameter of the alumina powder (particles) is about 7 m, then dry-milling the powder mixture for 10 h. And then preparing composite material according to the above manufacturing method described in Example 1. The thermal expansion curve of the composite material is as shown in FIG. 5. Comparing with the pure enamel material, the softening point is elevated up 120 C.

Example 6

(18) Preparing respectively the Al.sub.2O.sub.3 (30 wt %)-enamel (70 wt %) composite material coating, the Ni-20Co-25Cr-5Al-0.3Ce-0.5La-0.2Dy (10 wt %)-enamel (70 wt %)-Al.sub.2O.sub.3 (20 wt %) composite material coating, according to the preparing method described in Example 4, then cyclic oxidizing the samples at 1000 C., and in a cyclic oxidizing, heating for 60 min at 1000 C. and air-cooling for 15 min. The test of 100 cycles is carried out. The test results show that the two coatings have equivalent high temperature oxidation resistance and do not appear coating peeling, and the oxidation resistance of K38G alloy is significantly improved.

Example 7

(19) Preparing respectively the pure enamel composite coating material, other six Ni-25Cr-0.3Ce alloy-enamel composite coating materials, according to the preparing method described in Example 1, wherein the contents of the alloy are respectively 5%, 10%, 15%, 20%, 25%, 30% of the total amounts of the composite materials. The thermal expansion coefficient curves of the samples are measured (shown in FIG. 7). The test results show that the improved metal alloy content of the composite material benefits increasing the thermal expansion coefficient.

Example 8

(20) Preparing respectively multi-component alloy coatings on a single crystal high temperature alloy Rene N5 substrate and a model high temperature alloy Ni-20Al-10Mo (wt %), according to the preparing method described in Example 4, the specific compositions of the coatings are shown in described in Table 2. The cyclic oxidizing properties of the coatings are measured at 1050 C. In a cyclic oxidizing, heating for 60 min at 1050 C. and air-cooling for 15 min. The test of 100 cycles is carried out. The cyclic weight increase (the peeling amount included) and the peeling are shown in Table 3.

(21) TABLE-US-00002 TABLE 2 Compositions of the enamel composite coatings Alloy phase Hard particles Enamel Percentage Percentage Percentage No. Composition (wt %) (wt %) formula (wt %) (wt %) 1 Ni20.5Cr0.1La4.4Sr 10 90 2 Ni25Cr6Al0.5Hf0.5K 30 70 3 Ni20Co40.5Cr4Al0.5Hf 70 30 4 Ni20Co10Cr5Al0.5Hf0.5K 10 ZrO.sub.2 25 90 5 Ni20Cr12Al0.5Yb 10 SiO.sub.2 20 70 6 Ni25Cr0.5HF0.2Tb 40 Cr.sub.2O.sub.3 30 30 7 Ni22Co20.5Cr5Al0.5Hf 4 Si.sub.3N.sub.4 6 90 8 Ni30Cr8Al0.5Gd0.1N 20 AlN 10 70 9 Ni22Co40.5Cr4Al0.5Hf 60 BN 10 30 10 Ni20.5Cr0.1La4.4Sr 20 SiO.sub.2 5 60 Cr.sub.2O.sub.3 15 11 Ni20.5Cr0.1La4.4Sr 10 Al.sub.2O.sub.3 30 30 Ni20Co20.5Cr6Al0.1La0.4Dy 20 AlN 10 12 Ni25Cr6Al0.5Hf 10 Al.sub.2O.sub.3 10 60 Ni20Co20.5Cr6Al0.1La0.4DHf 15 ZrO.sub.2 5 13 Ni25Cr6Al0.5Hf 30 30 Ni20Co20.5Cr6Al0.1La0.4Dy 40 14 ZrO.sub.2 20 70 Al.sub.2O.sub.3 10

(22) TABLE-US-00003 TABLE 3 Depiction of the composite coatings and results after cyclic oxidation Weight No. of Thickness of change Spallatin Substrate coating coating (m) (mg/cm.sup.2) condition Rene N5 1 25 0.8 no Ni20Al10Mo 1 25 0.8 no Rene N5 2 25 0.4 no Ni20Al10Mo 2 25 0.4 no Rene N5 3 25 0.6 no Ni20Al10Mo 3 25 0.6 no Rene N5 4 25 0.7 no Ni20Al10Mo 4 25 0.6 no Rene N5 5 25 0.3 no Ni20Al10Mo 5 25 0.3 no Rene N5 6 25 0.4 no Ni20Al10Mo 6 25 0.5 no Rene N5 7 25 0.9 no Ni20Al10Mo 7 25 0.9 no Rene N5 8 25 0.4 no Ni20Al10Mo 8 25 0.4 no Rene N5 9 25 0.6 no Ni20Al10Mo 9 25 0.6 no Rene N5 10 25 0.3 no Ni20Al10Mo 10 25 0.3 no Rene N5 11 25 0.4 no Ni20Al10Mo 11 25 0.4 no Rene N5 12 25 0.3 no Ni20Al10Mo 12 25 0.3 no Rene N5 13 25 0.5 no Ni20Al10Mo 13 25 0.5 no Rene N5 14 15 0.8 Spall at corners after 15 cycles Ni20Al10Mo 14 15 3 Test ceased due to spallation after 10 cycles Rene N5 13 10 0.2 no 14 25 Ni20Al10Mo 13 10 0.2 no 14 25 Rene N5 13 30 0.1 no 12 30 14 40 Ni20Al10Mo 13 30 0.1 no 12 30 14 40

(23) The above examples are only used for illustrating the technical concept and features of the present invent. The purpose is to enable those skilled in the art to understand the content of the present invent and implement accordingly, but not to limit the scope of the present invent. It will be understood that modifications and alternatives without departing from the scope and spirit of the invention will be within the scopes of the following claims of the invention.