JPH06184722A - Thermal-spraying material and thermal-spraying coated member - Google Patents

Abstract

PURPOSE:To develop a roller superior in heat resistance, thermal shock resistance, high temp. corrosion resistance, and build-up resistance, etc., by forming a thermally sprayed layer comprising principally 2CaO, SiO2 and a specific metal and a specific metal compound on a surface of a roller for the inside of heat treatment furnace. CONSTITUTION:A thermal spraying material with a composition consisting of a metallic oxide of 35-95wt.% 2CaO, SiO2 and the balance at least one kind of component selected from among metallic oxides such as Al2O3, MgO, SiO2, etc., metallic carbides such as Cr3C2, NbC, Mo2C, etc., metallic borides such as CrB2, TiB2, etc., metallic silicates such as CrSi2, MoSi2, etc., and metals such as Co, Cr, Ni, Al, Y, etc., is thermally sprayed on the surface of the roller used in the inside of the heat treatment furnace. After a solution consisting essentially of a chromic acid was applied on the thermally sprayed layer, the thermally sprayed layer is baked at >=300 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal spray material for thermal spray coating for the purpose of surface modification of ceramics, metals and the like, and a coating member obtained by thermal spraying the thermal spray material onto a substrate.

[0002]

2. Description of the Related Art In industrial materials, various characteristics required for heat-resistant members have recently become more severe. For example, various properties such as heat resistance, heat shock resistance, and wear resistance have become extremely important in a severe operating environment. In addition, the longevity of the members by improving these characteristics is
Since these members are usually expensive, they are also important in terms of reducing the manufacturing cost.

For example, an in-furnace roll for heat treatment generally has a short life because it is used in a very harsh environment. Therefore, development of an in-furnace roll having excellent durability is strongly desired. There is. The in-furnace roll for heat treatment is used at a high temperature of 600 to 1200 ° C. in a reducing or oxidizing atmosphere. During use, the roll surface is significantly worn by the threading material, and iron oxide powder and other oxides are deposited on the roll surface, so-called build-up occurs.

When build-up occurs, the roll surface becomes convex, which causes flaws in the sheet-passing material, leading to deterioration in product quality. Therefore, when build-up occurs, the operation is stopped, and when the roll surface is heavily cared for or worn, the roll is replaced. Such maintenance work is frequently performed due to the poor durability of the current furnace rolls, and the operation must be stopped each time, which hinders planned production. This is also a factor that ultimately increases product costs.

Under these circumstances, there is a strong demand for a highly durable in-furnace roll, and in recent years, various types of thermal spraying rolls have been proposed and started to be used as one of measures for surface modification of the roll. This thermal spraying roll includes oxide ceramics thermal spraying rolls and cermet thermal spraying rolls with heat-resistant metals such as oxides or borides.Each of them has its advantages and disadvantages, so far it is satisfactory. A viable product has not been obtained.

That is, the cermet type thermal spraying roll is excellent in wear resistance and peeling resistance of the coating, but is insufficient in high temperature corrosion resistance and build-up resistance and cannot be used in a high temperature range. On the other hand, the ceramic-based thermal spraying roll has good build-up resistance, but has poor thermal shock resistance and abrasion resistance, and in particular has poor peeling resistance of the coating, so that the life of the roll is short and the practical advantage is not so great.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides heat resistance,
What is intended to obtain a thermal spray material having excellent properties such as thermal shock resistance, high temperature corrosion resistance, abrasion resistance, build-up resistance and film peeling resistance, and a thermal spray coating of the thermal spray material on the surface of a base material. Thus, the thermal spray coating member having the above-mentioned characteristics is obtained.

[0008]

This invention is 2CaO.
SiO ₂ is 35 to 95% by weight, and the balance is substantially at least one kind of metal oxide, metal carbide, metal boride, metal silicide and metal. 1) The metal oxide is selected from alumina, magnesia, silica, yttria and ceria, the metal carbide is selected from chromium carbide, niobium carbide, molybdenum carbide, titanium carbide and tantalum carbide, and the metal boride is chromium boride and titanium boride. And zirconium boride, the metal silicide is chromium silicide, molybdenum silicide, and zirconium silicide, and the metal is C.
The surface of the thermal spray material (claim 2) or the heat-resistant material according to claim 1, which is at least one selected from the group consisting of o, Cr, Ni, Al, Y, Ta and Hf. A metal coating layer having the heat resistance described above is formed, and the metal coating layer is further spray coated with the thermal spray material according to claim 1 or 2, and a thermal spray coating member (claim 3), A thermal spray coating member formed by treating the thermal spray coating layer provided on the thermal spray coating member according to claim 3 with a solution containing chromic acid as a main component, and then heat-treating this at 300 ° C. or higher. 4). Hereinafter, these inventions will be further described.

The thermal spray material of the invention of claim 1 is 2CaO.
SiO ₂ and the balance substantially metal oxides, metal carbides,
It is composed of at least one of metal boride, metal silicide and metal. 2CaO used in this invention
SiO ₂ has a very large coefficient of thermal expansion as an inorganic material, and shows a value similar to that of metal. Further, this material is characterized in that it has a relatively low melting point among inorganic materials, and its melt has a low viscosity, and therefore has a high meltability during thermal spraying.

The characteristics of 2CaO.SiO ₂ combined with the characteristics of the coefficient of thermal expansion described above form a unique coating structure when a thermal spray coating is formed. That is, these sprayed materials form a sufficiently melted coating on the substrate and shrink significantly during the subsequent cooling process. Then, due to the dimensional change accompanying the cooling shrinkage, a large number of fine cracks are generated in the structure of the thermal spray coating. This crack is several μm
Although it is extremely fine, it is characterized in that it is selectively generated in the direction perpendicular to the substrate. The fine vertical cracks act very effectively for thermal stress relaxation and give the thermal spray coating excellent thermal shock resistance.

Further, the 2CaO.SiO ₂ thermal spray coating is also characterized in that it has excellent build-up resistance and high-temperature corrosion resistance due to the chemical components contained and the specificity of the structure upon thermal spraying. Specifically, the wettability of the film is low with respect to various reactive components and corrosive components, that is, the reactivity is low, so that excellent build-up resistance and high temperature corrosion resistance are exhibited. On the other hand, it has the characteristic that it reacts more positively with vanadium and sulfur compounds to form stable compounds on the film surface, and acts as a protective film against new corrosive components.

The 2CaO.SiO ₂ sprayed coating shows excellent properties in terms of thermal shock resistance and high temperature corrosion resistance as described above, but on the other hand, the wear resistance of the coating is different from that of other ceramic sprayed materials. Equal or less than the comparison. Therefore, if this is used as a heat resistant member that is exposed to a severely worn environment, a problem occurs in durability.

Therefore, in the present invention, 2CaO.SiO ₂
At least one or more of a metal oxide, a metal carbide, a metal boride, a metal silicide and a metal is used as a material for improving its wear resistance without impairing various excellent properties of the above. When two or more of these additives are used in combination, the compounding ratio in that case is not particularly limited and is arbitrary. An appropriate blending ratio can be set depending on the use conditions.

2CaO.SiO ₂ and the above additives are
Although the thermal spray material of the present invention can be obtained by simply mixing these powders, the mixed powder is further slurried using a solvent such as water or ethanol, and this is granulated with a spray dryer to a particle size of 5 to 500 μm. It may be one.

[0015] In the present invention, 2CaO · SiO ₂ and metal oxide, metal carbide, metal boride, compounding ratio of the metal silicide and metal of at least one kind or more, the former 35-95
The latter, in weight percent, the balance being essentially the additive. Two
If the proportion of CaO · SiO ₂ is less than 35% by weight, a thermal sprayed coating having sufficient thermal shock resistance and high temperature corrosion resistance cannot be formed, and the buildup resistance is largely reduced. Also,
If it exceeds 95% by weight, the effect of the additive cannot be expected.

The invention of claim 2 specifies the metal oxide, metal carbide, metal boride, metal silicide and metal of the invention of claim 1, wherein the metal oxide is alumina, magnesia, silica or yttria. And ceria, the metal carbide is selected from chromium carbide, niobium carbide, molybdenum carbide, titanium carbide and tantalum carbide, the metal boride is selected from chromium boride, titanium boride and zirconium boride, Metal silicide is chromium silicide,
It is selected from molybdenum silicide and zirconium silicide, and the metal is Co, Cr, Ni, Al,
It is selected from Y, Ta and Hf.

[0017] As for the metal oxide in the mineral that consists of two or more of the above metal oxides, for example, mullite _{(3Al 2 O 3 · 2SiO 2} ), sillimanite (Al ₂ O ₃ · SiO ₂ ), Spinel (MgO.Al ₂
O ₃ ), cordierite (2MgO · 2Al ₂ O ₃ ·
5SiO ₂ ), Clinoenstatite (MgO · SiO)
_2), sapphirine _{(4MgO · 5Al 2 O 3 ·} 2SiO
It can also be used as ₂ ). It should be noted that these metal oxides, metal carbides, metal borides, metal suicides and metals can be used alone or in combination of two or more.

A third aspect of the present invention is a thermal spray coating member obtained by thermal spray coating the above thermal spray material. In order to spray the thermal spray material onto the base material, an intermediate layer having a heat resistance equal to or higher than that of the heat resistant material of the base material is previously formed on the surface of the base material, and the thermal spray material is spray-coated on the intermediate layer. By forming a coating layer of a heat-resistant metal equal to or more than the heat-resistant material of the above-mentioned base material between the base material and the thermal spray coating, the peel resistance is improved and an excellent thermal spray coating member is obtained. You can

The heat-resistant metal forming the intermediate layer used here is generally Co, Cr, Ni, Al, Y, T.
a, Hf and other heat resistant metals or alloys of these metals,
For example, Ni-Cr, Ni-Al, Ni-Cr-Al, C
An o-Ni-Cr-Al-Y alloy or the like is used.

Further, the invention of claim 4 is one in which the thermal spray coating layer on the surface of the thermal spray coating member of the invention of claim 3 is treated with a solution containing chromic acid as a main component, and further this is heat treated at 300 ° C. Therefore, it is possible to obtain a thermal spray coating member having further excellent build-up resistance and wear resistance of the coating. The reason is that an oxide containing Cr ₂ O ₃ as a main component is formed. The heat treatment temperature is preferably 400 ° C. or higher in terms of reaction. Although a silicate-based pore-sealing agent can be added and a ceramic coating agent can be used in combination, it was confirmed that a chromic acid-based material that produces Cr ₂ O ₃ is the best.

The treatment of chromic acid here is carried out, for example, with a concentration of 3
The surface of the thermal spray coating member is brushed or sprayed with a 0% chromic acid solution and heated and dried at several tens of degrees for about 10 minutes. Then, this is heated at 300 ° C. or higher. The upper limit of the heating temperature is usually 600 ° C. The processing time is approximately 60 minutes.
If the heating temperature here is less than 300 ° C., the above oxide cannot be obtained, and the effect cannot be expected.

In order to form a thermal spray coating on the surface of a roll for a heat treatment furnace using the thermal spray material of the present invention, a method such as plasma solvent, explosive spray, high speed flame spray, or ordinary gas spray can be used. . However, when a high melting point ceramic material is sprayed, it is difficult to form a sufficiently molten and good coating by the methods of explosion spraying and gas spraying, and the metal or alloy may be decomposed and oxidized.

Therefore, in general, the plasma spraying method or the high speed flame spraying method, which has a high flame temperature, can form a good film even with a high melting point ceramic, and is less likely to decompose a metal or an alloy, is preferable.

[0024]

[Function] 2CaO / SiO ₂ has excellent properties such as thermal shock resistance and high temperature corrosion resistance, but the wear resistance of the coating is not necessarily equal to or less than that of other ceramic materials. . On the other hand, metal oxides, metal carbides, metal borides, metal suicides, and metals such as Co, Cr, Ni, Al, Y, Ta, H.
f is extremely excellent in wear resistance. Therefore, in the present invention, by using 2CaO.SiO ₂ and these additives in a prescribed ratio to prepare a thermal spray material, finally, build-up resistance, heat resistance, thermal shock resistance, high temperature corrosion resistance, and abrasion resistance are obtained. It is intended to obtain a thermal spray material excellent in all properties.

[0025]

【Example】

 (Examples 1 to 67, 70 to 99)

On the surface of the SUS304 substrate, a sprayed coating as shown in Tables 1 to 14 and an intermediate layer as shown in the same table were formed by thermal spraying, and the following tests were carried out on those without the intermediate layer. , Its build-up resistance (MN value), wear resistance (DS / mg), and peel resistance (times) were determined.

The results are shown in Tables 1-14. In the same table, the treatment of the solution containing chromic acid as a main component shows the case where a 30% chromic acid solution was applied and baked at 450 ° C. for 30 minutes, and the mark ◯ indicates that the treatment was carried out. Further, Δ in the performances in the table indicates a characteristic defect. The thermal spray coating composition is a value of material constituent components.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

[0032]

[Table 5]

[0033]

[Table 6]

[0034]

[Table 7]

[0035]

[Table 8]

[0036]

[Table 9]

[0037]

[Table 10]

[0038]

[Table 11]

[0039]

[Table 12]

[0040]

[Table 13]

[0041]

[Table 14]

The build-up resistance was determined by the method shown in FIG. As shown in the figure, between the two thermal spray member test pieces (B
Surface, C surface) and the upper surface (A surface) of the sprayed member test piece 1 are sprayed with the buildup raw material 2 and adjusted to the conditions shown in Table 15, and as shown in FIG. A reciprocating motion was performed while applying a load to evaluate the buildup status of each surface of A, B, and C. The evaluation was performed based on the total score (9 out of 9) obtained according to the criteria shown in Table 16 below.

The wear resistance was determined by a Suga-type wear test conducted by the apparatus shown in FIG. In this test, as shown in FIG. 2, the thermal spray member test piece 1 is reciprocated to cause frictional wear between the thermal spray coating 3 and a disk having an emery paper 4 wound around the outer periphery thereof. The disk rotates such that the test piece rotates 0.9 degrees each time the test piece reciprocates, and a new surface is constantly contacted. The type of emery paper and the load here are as shown in Table 17.

Further, the abrasion resistance was indicated by the number of reciprocations (DS / mg) of the test piece required to wear 1 mg. Further, the peel resistance was determined by applying the thermal shock shown in Table 18 and the number of times until the peeling of the film occurred.

[0045]

[Table 15]

[0046]

[Table 16]

[0047]

[Table 17]

[0048]

[Table 18]

Tables 19 to 23 show Comparative Example 1 for the composition of the thermal spray coating outside the range specified in the present invention.
.About.16. As shown in the table, it can be seen that all of the comparative examples are inferior in build-up resistance, abrasion resistance and peeling resistance, and a good thermal spray coating cannot be obtained.

[0050]

[Table 19]

[0051]

[Table 20]

[0052]

[Table 21]

[0053]

[Table 22]

[0054]

[Table 23]

[0055]

According to the thermal spray material of the present invention, a thermal spray coating having excellent build-up resistance, heat resistance, and thermal shock resistance can be formed. High reliability can be obtained with excellent impact resistance, peeling resistance, high temperature corrosion resistance, and abrasion resistance. Therefore, for example, according to this, the life of the heat treatment roll or the like can be greatly extended.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of a tester for testing build-up resistance of a portion having a sprayed coating according to the present invention.

FIG. 2 is a schematic explanatory view of a tester for testing the wear resistance of a member having a sprayed coating according to the present invention.

[Explanation of Codes] 1 ... Sprayed member test piece, 2 ... Build-up raw material, 3 ... Sprayed coating, 4 ... Emery paper.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoru Kawazoe 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corp. Kimitsu Works premises Nippon Steel Hard Co., Ltd. Kimitsu Works (72) Inventor Kazuyuki Sashiyama Fukuoka 46 Nakahara, Tobata-ku, Kitakyushu, Japan Prefecture Nippon Steel Co., Ltd. Yawata Works Tobata Campus, Nippon Steel Hard Co., Ltd., Tobata Works (72) Inventor Takuya Tsuda 46 Nakahara, Tobata-ku, Kitakyushu, Fukuoka Prefecture Nippon Steel Corporation Yawata Works Tobata premises Nittetsu Hard Co., Ltd. Tobata Works

Claims (4)

[Claims] 1. The content of 2CaO.SiO ₂ is 35 to 95% by weight.
And the balance is substantially at least one of a metal oxide, a metal carbide, a metal boride, a metal silicide, and a metal. 2. The metal oxide is selected from alumina, magnesia, silica, yttria and ceria, the metal carbide is selected from chromium carbide, niobium carbide, molybdenum carbide, titanium carbide and tantalum carbide, and the metal boride is chromium boride and titanium. Among the boride and zirconium boride, the metal silicides are chromium silicide, molybdenum silicide and zirconium silicide, and the metals are Co and C.
The thermal spray material according to claim 1, which is at least one selected from r, Ni, Al, Y, Ta, and Hf. 3. A metal coating layer having heat resistance equal to or higher than that of the heat resistant material is formed on the surface of the heat resistant material,
Furthermore, a thermal spray coating member is obtained by spray coating the thermal spray material according to claim 1 or 2 on the metal coating layer. 4. A thermal spray coating obtained by treating the thermal spray coating layer provided on the thermal spray coating member according to claim 3 with a solution containing chromic acid as a main component, and then heat-treating this at 300 ° C. or higher. Cover member.