Thermal spraying material

Abstract

To provide a calcium silicate thermal spray material having performance excellent in corrosion resistance and peeling resistance, etc., without causing a spitting phenomenon etc., by pulverization when depositing a thermal spray film and having excellent thermal spray coating deposition.SOLUTION: A calcium silicate thermal spray material has more than 1 of the peak ratio (β-Ca2SiO4 / γ-Ca2SiO4) of a single peak diffraction intensity of β-Ca2SiO4 detected at 2θ=30.75-31.35 in the diffraction intensity of a crystal phase measured using an X-ray diffraction method to a single peak diffraction intensity of γ-Ca2SiO4 detected at 2θ=20.25-20.85.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a thermal spraying material used for forming a thermal spray coating on the surface of metals, ceramics, cermets, etc.

Background Art

[0002] A thermal spray coating is formed by spraying a thermal spraying material onto a substrate. Thermal spray coatings are used in various applications depending on the properties of the thermal spraying material. As application examples of thermal spray coatings, they are widely applied to various applications that require wear resistance, heat resistance, and corrosion resistance, such as automobile engines, aircraft engines, semiconductor manufacturing equipment, rolls for transporting steel sheets, and wear-resistant applications in general industries.

[0003] Conventionally, various studies have been conducted for the development of new thermal spraying materials. For example, in Patent Document 1, a calcium silicate-based thermal spraying material manufactured by spray granulating γ-2CaO·SiO2 powder has been proposed. In this method, a slurry obtained by wet pulverizing a material obtained by sintering and synthesizing γ-2CaO·SiO2 is granulated to produce a thermal spraying material. However, there is a problem that the slurry viscosity becomes unstable due to the hydration-active substances contained in the material, and the slurry solidifies. Further, when sintering and synthesizing γ-2CaO·SiO2 after granulating the raw materials, a phase transition from the β-phase to the γ-phase occurs around 550°C during the cooling process of the sintering synthesis. The phase transition from the β-phase to the γ-phase is accompanied by a rapid volume change and causes tissue collapse, resulting in defects in the material. Therefore, the particle size distribution becomes finer, which becomes a factor causing spitting during the formation of the thermal spray coating.

[0004] Note that spitting refers to a phenomenon in which deposits formed by the adhesion and accumulation of over-melted thermal spraying powder on the inner wall of the nozzle of the thermal spraying device are mixed into the thermal spray coating. The more fine particles the thermal spraying powder contains, the more likely spitting is to occur. When spitting occurs, the tissue structure of the thermal spray coating becomes non-uniform, so the quality of the thermal spray coating is significantly reduced.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 7-100847 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] An object of the present invention is to provide a calcium silicate thermal spraying material excellent in thermal spraying film formability capable of suppressing the occurrence of spitting phenomenon when a thermal spraying film is formed. [Means for Solving the Problems]

[0007] The present invention provides a thermal spraying material for a calcium silicate thermal spraying material, in which the peak ratio (β-Ca2SiO4 / γ-Ca2SiO4) of the single peak diffraction intensity of β-Ca2SiO4 detected at 2θ = 30.75 to 31.35 and the single peak diffraction intensity of γ-Ca2SiO4 detected at 2θ = 20.25 to 20.85 in the diffraction intensity of the crystal phase measured by the X-ray diffraction method is greater than 1. The technical idea that the peak ratio (β-Ca2SiO4 / γ-Ca2SiO4) is greater than 1 also includes the case where the peak of β-Ca2SiO4 is detected when the peak of γ-Ca2SiO4 is not detected and is substantially zero.

[0008] The calcium silicate material has a CaO-SiO2-based composition, but in the present invention, a 2CaO-SiO2-based composition material is used. The 2CaO-SiO2-based calcium silicate material has several crystal phases (α, α´, β, and γ), but at normal temperature and pressure, it has the γ phase as a stable crystal phase.

[0009] The present invention has found that by making the composition ratio of CaO and SiO2 rich in CaO, it can be stabilized as the β-phase after sintering, and since the transition from the β-phase to the γ-phase does not occur, the volume change associated therewith does not occur, and spitting associated with pulverization can be prevented. At this time, in order for the β-phase to be sufficiently formed to the extent that pulverization can be prevented, in the diffraction intensity of the crystal phase measured using the X-ray diffraction method, the peak ratio (β-Ca2SiO4 / γ-Ca2SiO4) of the single-peak diffraction intensity of β-Ca2SiO4 detected at 2θ = 30.75 to 31.35 and the single-peak diffraction intensity of γ-Ca2SiO4 detected at 2θ = 20.25 to 20.85 should be greater than 1. The above peak ratio may be greater than 3, and furthermore, if it is greater than 5, a more stable β-phase is formed, which is preferable.

[0010] Since the calcium silicate thermal spraying material of the present invention has a stable β-phase formed, pulverization due to volume change can be prevented, and the particle size is not too small compared to γ-Ca2SiO4 powder. Specifically, in the particle size distribution measured using the laser diffraction method, it is preferable that the ratio of the particle size in terms of volume being 15 μm or less is less than 20%. Also, in the particle size distribution measured using the laser diffraction method, it is preferable that the ratio of the particle size in terms of volume being 10 μm or less is less than 10%.

[0011] When the ratio of the particle size in terms of volume being 15 μm or less in the particle size distribution measured using the laser diffraction method is less than 20%, the occurrence of spitting can be prevented when forming a thermal spray coating, and the surface roughness of the formed thermal spray coating tends to decrease.

[0012] When the ratio of the particle size in terms of volume being 10 μm or less in the particle size distribution measured using the laser diffraction method is less than 10%, the occurrence of spitting can be prevented when forming a thermal spray coating, and the surface roughness of the formed thermal spray coating tends to decrease.

[0013] In a calcium silicate thermal spraying material, in order to increase the peak ratio (β-Ca2SiO4 / γ-Ca2SiO4) of the single-peak diffraction intensity of β-Ca2SiO4 detected at 2θ = 30.75 to 31.35 and the single-peak diffraction intensity of γ-Ca2SiO4 detected at 2θ = 20.25 to 20.85 in the diffraction intensity of the crystal phase measured by X-ray diffraction method and obtain a stable β-phase, the composition ratio of CaO and SiO2 should be made CaO-rich. In particular, it is preferable that the molar ratio of the Ca component and the Si component (CaO mol amount / SiO2 mol amount) in terms of oxides is greater than 2.0.

[0014] The thermal spraying material of the present invention can reduce the angle of repose. The angle of repose is preferably about 30 to 37 degrees. Within this range, during the formation of the thermal spray coating, the supply of the thermal spraying material can be carried out smoothly, the supply speed can be increased, and various troubles in the hopper can be prevented.

[0015] The "angle of repose" means the bottom angle calculated from the diameter and height of the conical deposit formed by dropping a powder material from a funnel of a certain height onto a horizontal substrate. Such an angle of repose can be measured in accordance with the provisions of JIS R 9301-2-2:1999 "Methods for Measuring Physical Properties of Alumina Powder - 2: Angle of Repose".

[0016] [Manufacturing method of thermal spraying material] The thermal spraying material of the present invention is not necessarily limited thereto, but after granulating the raw material powder, it is preferably sintered to form a stabilized spherical shape. For example, the raw material powder is mixed with water, a solvent, and optionally a binder, stirred to form a slurry, granulated, the granulated powder is fired and sintered, and then classified as necessary to obtain the thermal spraying material.

[0017] [Preparation of raw materials] First, prepare the raw materials for the thermal spraying material. As the raw materials, for example, powders of CaCO3 and SiO2 can be used. These raw materials include Al2O 3、FeO2 and the like are often contained as impurities. The properties of the powder used as the raw material are not particularly limited, but in order to form a mixed crystal with a uniform composition, for example, the average particle size is preferably fine, about 0.1 μm or more and 10 μm or less. The average particle size is, for example, the particle size (median diameter) at which the cumulative frequency based on the volume-based particle size distribution measured by the laser diffraction method is 50%. In the composition after granulation and sintering, it is preferable to adjust the molar ratio of CaCO3 and SiO2 so that the molar ratio of CaO to SiO2 is 2 or more. The molar ratio of CaO and SiO2 is calculated as the molar ratio when the Ca component and Si component by fluorescent X-ray analysis (XRF) are converted to CaO and SiO2, respectively.

[0018] <Granulation> Next, the prepared raw material powder is granulated into a spherical shape to produce granulated powder. By going through this granulation process, it is possible to prevent the generation of angular particles in the subsequent firing process, and a spherical spraying material with excellent fluidity can be preferably obtained. The granulation method is not particularly limited, and various known granulation methods can be adopted. For example, one or more of the methods such as tumbling granulation method, fluidized bed granulation method, stirring granulation method, compression granulation method, extrusion granulation method, crushing granulation method, and spray granulation method using a spray dryer can be adopted. From the viewpoint of being able to uniformly mix the raw material powder simply and with high precision through a dispersion medium, the spray granulation method using a spray dryer can be preferably adopted. The type of the dispersion medium used in the spray granulation method using a spray dryer is not particularly limited, and examples include water, lower alcohols (for example, alcohols having 5 or less carbon atoms such as methanol, ethanol, and propanol), and mixtures thereof. Further, a binder can be added to the dispersion medium as necessary. The granulation conditions depend on the apparatus used and thus cannot be generally stated, but for example, it is preferable to granulate in a temperature range of 400 °C or lower in the atmosphere (for example, the drying temperature is about 120 °C to 300 °C). The size of the granulated particles in the granulated powder may be determined in consideration of the average particle size of the raw material powder and the shrinkage due to the subsequent firing process.

[0019] <Firing> Thereafter, the granulated powder is fired. In firing, the individual raw material particles contained in the granulated particles are sintered. During such sintering, the raw material components diffuse into each other to form a solid solution. In the thermal spraying material of the present invention, it is preferable to sufficiently sinter or melt the raw material particles contained in the granulated particles and integrate them. That is, it is preferable to integrate them to such an extent that the form of the granulated body can hardly be seen. Examples of the conditions for firing and melt integration include firing at about 1300°C in an air atmosphere. The firing time is not particularly limited because it depends on the form of the granulated particles, but for example, about 4 hours can be used as a guide. For firing the granulated powder, general batch-type firing furnaces, continuous firing furnaces, etc. can be used without particular limitation. The firing atmosphere can be used without particular limitation, such as an air atmosphere or an inert atmosphere. Although not an essential step, if necessary, steps such as crushing and classifying the fired product after firing may be included. Thereby, the thermal spraying material disclosed herein can be obtained.

[0020] It is important to obtain firm particles by sufficiently sintering the granulated powder in the sintering process. Also, when using calcium carbonate as a raw material, it should be noted that by sufficiently decarbonizing in the sintering process, carbon dioxide gas will not be generated during thermal spraying to prevent the formation of a dense coating.

[0021] <Thermal spray coating> By thermal spraying the above thermal spraying material, a thermal spray coating can be formed. This thermal spray coating is provided on the surface of the base material and is provided as a member with a thermal spray coating or the like. Hereinafter, such a member with a thermal spray coating and the thermal spray coating will be described. The thermal spraying material of this invention can be thermally sprayed by a gas thermal spraying method or a plasma thermal spraying method.

[0022] This sprayed coating is provided on the surface of a substrate, and can impart, for example, corrosion resistance and heat resistance to the substrate. The substrate (substrate to be sprayed) to be sprayed is not particularly limited. For example, when the substrate is subjected to spraying of such a sprayed material, as long as it is a substrate made of a material that can have desired resistance, its material, shape, etc. are not particularly limited. Examples of the material constituting such a substrate include various metals or alloys. Specifically, for example, aluminum, aluminum alloy, iron, steel, copper, copper alloy, nickel, nickel alloy, gold, silver, bismuth, manganese, zinc, zinc alloy, etc. are exemplified. Among them, steel represented by various SUS materials (which may be so-called stainless steel) having a relatively large coefficient of thermal expansion among general-purpose metal materials, heat-resistant alloys represented by Inconel, low-expansion alloys represented by Invar, Kovar, etc., corrosion-resistant alloys represented by Hastelloy, and substrates made of aluminum alloys represented by 1000 series to 7000 series aluminum alloys useful as lightweight structural materials, etc. can be mentioned. For example, since the calcium silicate-based sprayed material of the present invention has low reactivity with molten metal and a coefficient of thermal expansion close to that of stainless steel-based materials, it may be used, for example, for coating stainless steel-based materials exposed to contact with molten metal in a molten zinc plating process or the like.

[0023] As the spraying method for spraying the spraying material, various known spraying methods can be adopted. For example, preferably, spraying methods such as plasma spraying method, high-velocity flame spraying method, flame spraying method, explosion spraying method, etc. can be adopted.

[0024] The plasma spraying method is a spraying method that uses a plasma flame as a spraying heat source for softening or melting a spraying material. When an arc is generated between electrodes and an operating gas is turned into plasma by such an arc, such a plasma flow ejects from a nozzle as a high-temperature and high-speed plasma jet. The plasma spraying method generally includes a coating technique of obtaining a sprayed coating by injecting a spraying material into this plasma jet, heating and accelerating it, and depositing it on a base material. Note that the plasma spraying method can be in modes such as atmospheric plasma spraying (APS) performed in the atmosphere, low-pressure plasma spraying (LPS) performed at a pressure lower than atmospheric pressure, and high-pressure plasma spraying performed in a pressure vessel at a pressure higher than atmospheric pressure. According to such plasma spraying, for example, as an example, by melting and accelerating a spraying material by a plasma jet of about 5000°C to 10000°C, the spraying material can be made to collide with and deposit on a base material at a speed of about 200 m / s to 600 m / s.

Example

[0025] <Example 1> As Example 1, using CaCO3 and SiO2 powders having the raw material charging composition shown in Table 1 as raw materials, water and polyvinyl alcohol were added thereto and mixed with a stirrer, and then spray granulated with a spray dryer having a hot air temperature of 250°C to obtain granulated powder. When the obtained granulated powder was subjected to particle size analysis, it had the median diameter and particle size distribution shown in Table 1. The median diameter and the particle size distribution were measured using a laser diffraction particle size distribution measuring device Mastersizer 3000 manufactured by Malvern Panalytical.

[0026] Next, this granulated powder was fired in a heating furnace at a temperature of 1300°C for about 4 hours to obtain a sintered powder. The obtained sintered powder was sieved through a 75-μm sieve for classification to obtain a product powder (spraying material). When particle size analysis was performed on this product powder, it had a median diameter and particle size distribution as shown in Table 1. The median diameter and particle size distribution were measured using a laser diffraction particle size distribution measuring device Mastersizer 3000 manufactured by Malvern Panalytical Co., Ltd.

[0027] In addition, the results of measuring the chemical composition (molar ratio of CaO, SiO2, and Fe2O3 + AL2O3), X-ray diffraction intensity of the crystal phase (single-peak diffraction intensity of β-Ca2SiO4 detected at 2θ = 30.75 to 31.35 and single-peak diffraction intensity of γ-Ca2SiO4 detected at 2θ = 20.25 to 20.85), and angle of repose of this product powder are shown in Table 1. The chemical composition of the product powder was measured using a fluorescent X-ray analyzer LAB CENTER XRF-1800 manufactured by Shimadzu Corporation, with the voltage of the X-ray generating part set at 40 kV and the current at 95 mA. The sample actually measured by XRF was a glass bead prepared using a bead & fuse sampler TK-4100 type manufactured by Tokyo Kagaku Co., Ltd., in which lithium tetraborate, which is a flux component, was added and mixed at 10 mass% to the product powder. As the X-ray diffractometer, UltimaIV manufactured by Rigaku Corporation was used, and the measurement was performed under the conditions of using CuKα ray as the X-ray source, an acceleration voltage of 40 kV, an acceleration current of 10 mA, a scanning range of 2θ = 10° to 70°, a scanning speed of 10° / min, and a sampling width of 0.01°. At this time, the divergence slit was adjusted to 1°, the divergence vertical limiting slit was adjusted to 10 mm, the scattering slit was adjusted to 8 mm°, the receiving slit was opened, and the offset angle was adjusted to 0°. The angle of repose was a value obtained by subjecting each powder material to an A.B.D. powder property measuring instrument (manufactured by Tsutsui Rikagaku Kikai Co., Ltd., ABD-72 type) in accordance with JIS R 9301-2-2:1999.

[0028]

Table 1

[0029] <Examples 2 to 4, Comparative Examples 1 and 2> In Examples 2 to 4, Comparative Examples 1 and 2, only the ratios of CaCO3 and SiO2 powders as the raw material charging composition were changed to the ratios shown in Table 1 respectively. Granulation and sintering were carried out in the same manner as in Example 1. For the granulated particles and product powders, particle size analysis was performed, and they had the median diameters and particle size distributions shown in Table 1. Also, the chemical compositions, diffraction intensities of the crystal phases, and repose angles of these product powders were measured by the same method as in Example 1, and the results are shown in Table 1.

[0030] <Comparative Example 3> As Comparative Example 3, the same CaCO3 and SiO2 powders as in Comparative Examples 1 and 2 were used as raw materials, and sintering was carried out by firing in a heating furnace at a temperature of 1300 °C for about 4 hours, followed by pulverization. Then, water and polyvinyl alcohol were added and mixed with a stirrer, but it became highly viscous and solidified during the slurry formation, and granulated powder could not be obtained.

[0031] <Properties of Product Powder> Table 1 shows the results of measuring the shrinkage rate from the granulated powder for the obtained product powder. The shrinkage rate was calculated as "(median diameter of granulated powder - median diameter of product powder) / median diameter of granulated powder × 100" based on the median diameter. As shown in Table 1, in Examples 1 to 4, the shrinkage rate was as low as 25% or less, while in Comparative Examples 1 and 2, it exceeded 45% and the shrinkage was large. For Comparative Examples 1 and 2, during the cooling process of the sintering synthesis, with the phase transition from the β-phase to the γ-phase around 550 °C, a rapid volume change occurred, causing tissue collapse, resulting in the pulverization of the particle size distribution and thus an increase in the shrinkage rate.

[0032] While the molar ratio of CaO / SiO2 in the chemical composition of the product powders of Examples 1 to 4 was 2 or more, the molar ratio of CaO / SiO2 in Comparative Examples 1 and 2 was less than 2. Also, in terms of X-ray diffraction intensity, the peak ratio (β-Ca2SiO4 / γ-Ca2SiO4) of the single-peak diffraction intensity of β-Ca2SiO4 detected at 2θ = 30.75 - 31.35 and the single-peak diffraction intensity of γ-Ca2SiO4 detected at 2θ = 20.25 - 20.85 was greater than 1 in Examples 1 to 4, whereas no single peak of β-Ca2SiO4 was detected in Comparative Examples 1 and 2. That is, in Comparative Examples 1 and 2, the same peak intensity ratio was 0.0, indicating that the β-phase was not substantially formed.

[0033] Also, for the obtained product powders, in accordance with JIS R 9301-2-2:1999, the angle of repose was measured by subjecting each product powder to an A.B.D. powder property measuring instrument (manufactured by Tsutsui Rikagaku Kikai Co., Ltd., model ABD-72). As a result, in Examples 1 to 4, the angle of repose was in the range of 33 - 36 degrees, while in Comparative Examples 1 and 2, they were 41.0 degrees and 37.9 degrees respectively, which were larger than those in the examples.

[0034] <Properties of the Sprayed Coating> Next, using the products of Examples 1 to 4 and Comparative Examples 1 and 2, plasma spraying was carried out on SUS316L as the substrate by the following method. For the sprayed coating, the presence or absence of spitting and the surface roughness were measured. For the presence or absence of spitting, the surface of the coating was visually observed, and those without spitting were judged as "none", and those with even one spitting confirmed were regarded as "present". Specifically, spitting refers to the deposits on the surface of the coating having a size of 0.3 mm or more in diameter. The surface roughness was measured in accordance with the method specified in JIS B0601. Using a surface roughness meter "SV-3000S CNC" manufactured by Mitutoyo Corporation, the surface roughness was measured at any 5 points on the surface of the substrate (the surface to be sprayed), and the average value of the surface roughness of the 5 measured points was taken as the surface roughness of the substrate surface. Also, as a result of the surface roughness, the results of the arithmetic mean roughness Ra and the maximum height roughness Rz are shown in Table 1.

[0035] <Plasma Spraying Conditions> Using the SG-100 plasma made by PRAXAIR as the spraying machine, plasma spraying was carried out under the following conditions. Ar partial pressure: 50 psi He partial pressure: 50 psi Plasma output: 35 kW Powder flow rate: 9 g / min Substrate: Stainless steel SUS316L blasted with alumina #40 Spraying distance: 120 mm Coating thickness: 200 - 300 μm Traverse speed: 400 mm / sec Cooling method: Air cooling

[0036] Table 1 shows the results of measuring the presence or absence of spitting and the surface roughness of the sprayed coating respectively. In Examples 1 - 4, a sprayed coating was formed without spitting, while in Comparative Example 1, the supply of the spraying material was impossible and no coating could be formed in the first place. In Comparative Example 2, a sprayed coating could be formed but spitting occurred and the surface roughness deteriorated. Examples 1 - 4 were able to suppress spitting, had no problems with the supply of the spraying material, etc., and were excellent in the formability of the sprayed coating.

Claims

1. β-Ca 2 SiO 4 A calcium silicate thermal spraying material having a crystalline phase, wherein β-Ca is detected at 2θ = 30.75 to 31.35 in the diffraction intensity of the crystalline phase measured using the X-ray diffraction method 2 SiO 4 The peak ratio of the single peak diffraction intensity of and the single peak diffraction intensity of γ-Ca2SiO4 detected at 2θ = 20.25 to 20.85 (β-Ca 2 SiO 4 / γ-Ca 2 SiO 4 ) is greater than 1, A thermal spraying material having an angle of repose measured based on the provisions of JIS R 9301-2-2:1999 of 30 to 37°.

2. The thermal spraying material according to Claim 1, wherein, in the particle size distribution measured using the laser diffraction method, the proportion of particles having a particle diameter of 15 μm or less in terms of volume conversion is less than 20%.

3. The thermal spraying material according to Claim 1 or 2, wherein, in the particle size distribution measured using the laser diffraction method, the proportion of particles having a particle diameter of 10 μm or less in terms of volume conversion is less than 10%.

4. The spraying material according to any one of claims 1 to 3, which is a composition having a molar ratio of Ca component to Si component in terms of oxide (molar amount of CaO / molar amount of SiO 2 ) greater than 2.0.

Images