阅读说明：本技术 用于耐火产品的保护层 (Protective layer for refractory products ) 是由 伊莎贝拉·卡波迪 弗雷德里克·霍夫曼 皮埃尔里克·法比安·维斯帕 于 2019-07-26 设计创作，主要内容包括：一种用于处理包含超过10质量％的ZrO-2的熔凝耐火产品或“基础产品”的方法,所述方法包括以下步骤：a)加热所述产品的表面的至少一部分,以使ZrO-2晶体在小于2000μm的深度上延伸的表面区域中熔化；和b)冷却在前一步骤中获得的熔化的表面区域,以获得保护层。(For treating a material containing more than 10 mass% of ZrO 2 The method of fusing a refractory product or "base product" of (a), said method comprising the steps of: a) heating at least a portion of the surface of the product to cause ZrO 2 The crystals melt in a surface region extending over a depth of less than 2000 μm; and b) cooling the melted surface region obtained in the preceding step to obtain a protective layer.)

1. For treating a material containing more than 10 mass% of ZrO₂The method of fusing a refractory product or "base product" of (a), said method comprising the steps of:

a) heating at least a portion of the surface of the product or "surface to be treated" to cause ZrO in a superficial region extending to a depth of less than 2000 [ mu ] m₂Melting, or "remelting", the crystals; and

b) cooling the melted superficial region obtained in the previous step to obtain a protective layer;

c) optionally at least partially recrystallizing the zirconium oxide present in the amorphous phase of the protective layer,

in said method, in step a), the surface to be treated is irradiated with an incident laser beam or plasma radiation beam, the power per unit area of the incident beam being greater than 5000W/mm²。

2. The method according to the preceding claim, wherein in step a) the surface to be treated is heated to a temperature higher than 2500 ℃.

3. The method according to any one of the preceding claims, wherein in step a) the surface to be treated is heated so as to melt the base product over a depth of less than 1000 μ ι η.

4. A method according to any one of the preceding claims, wherein in step a) the surface to be treated is heated so as to melt the base product over a depth of more than 50 μ ι η.

5. The method of any one of the preceding claims, wherein in step b) the melted region is cooled by exposing the melted region to open air.

6. The method of any one of the preceding claims, wherein in step b) the cooling rate of the melted region is greater than 100 ℃/sec.

7. A method according to any one of the preceding claims, wherein in step a) the surface to be treated is fed with more than 50J/mm³Is the ratio of the power per unit area of the beam to the speed of travel of the incident beam over the surface to be treated.

8. Method according to the immediately preceding claim, wherein in step a) the surface to be treated is fed with more than 100J/mm³The exposure energy of (a).

9. A method according to any one of the preceding claims, wherein the surface to be treated comprises more than 10% of the surface of the base product.

10. The method of any one of the preceding claims, wherein the base product has the following composition:

10％<ZrO₂<98 percent; and/or

0.5％<Al₂O₃<70 percent; and/or

1.5％<SiO₂<40％；

The condition is 90 percent<ZrO₂+Al₂O₃+SiO₂Preferably 95%<ZrO₂+Al₂O₃+SiO₂。

11. The method of any one of the preceding claims, wherein the base product comprises more than 80 mass% ZrO₂。

12. The method according to any one of claims 1 to 11, wherein the base product has a composition such that, in mass percentage on the basis of the oxides, for a total of more than 90%:

-ZrO₂: 26% to 45%;

-Al₂O₃: 40% to 60%;

-SiO₂: 5% to 35%;

or such that:

-ZrO₂: 50% to less than 80%;

-Al₂O₃: 15% to 30%;

-SiO₂: 5% to 15%;

or such that:

-ZrO₂：≥80％；

-Al₂O₃：≥5％；

-SiO₂：≤12％；

or such that:

-10％<ZrO₂≤25％；

-50％<Al₂O₃<75％；

-5％<SiO₂<35％。

13. use of the treatment method according to the invention for plugging cavities present on a surface to be treated which extends continuously from the edge of the cavity over a distance of not more than 10 mm.

14. A fused refractory product protected with a protective layer, preferably manufactured according to the method of any one of claims 1 to 13, comprising more than 10 mass% ZrO below the protective layer₂And the protective layer:

-contains more than 10 mass% of ZrO₂；

-has a thickness of less than 2000 μm; and

-for more than 50% by volume, containing an amorphous phase and/or zirconia crystallites, the zirconia crystallites having an average surface area of less than 5 μm²。

15. Product according to the immediately preceding claim, in which the zirconia crystallites have an average surface area of less than 2 μm²。

16. Product according to either of the two immediately preceding claims, in which the protective layer has a porosity of less than 5%, the porosity being the percentage of the surface area occupied by pores in a section perpendicular to the surface to be treated.

Technical Field

The invention relates to a fused refractory product, in particular a block, at least partially covered with a protective layer.

The invention also relates to a method for treating the surface of an uncoated refractory product by irradiation with laser radiation to obtain a product according to the invention.

Finally, the invention relates to a glass melting furnace whose furnace lining comprises at least one block according to the invention.

Background

Among refractory blocks, there are distinct agglomerates (well known for building glass or metal melting furnaces) and sintered blocks.

Unlike sintered compacts, fused compacts generally contain an intergranular amorphous phase linking the grains. Therefore, the problems encountered with sintered and fused masses and the technical solutions adopted to solve them are generally different. Thus, the compositions developed for the manufacture of sintered masses cannot in principle be used per se for the manufacture of fused masses and vice versa.

The fused mass, commonly referred to as "electric frit", is obtained by melting a mixture of suitable starting materials in an electric arc furnace or by any other suitable technique. The molten material is then typically cast in a mold and then solidified. Typically, the obtained product is then subjected to a controlled cooling cycle to bring it to ambient temperature without breaking.

The fused mass for the refractory lining of glass furnaces may generally contain 10 to 95% ZrO₂。

With low or medium ZrO₂The content of lumps has good properties, but there is still room for improvement in terms of exudation and erosion by molten glass or its vapours.

With high or very high ZrO₂The fused mass of the content (VHZC) usually contains more than 80 mass%, or even more than 85 mass% or even more than 90 mass% ZrO₂Due to its extremely high corrosion resistance and not to make the productIs known for its ability to stain glass, not create defects in the glass and only bleed out in small amounts. There is still room for improvement in their resistance to glass vapors.

US 2007/0141348 describes a refractory product whose surface is exposed to laser radiation to reduce the reactivity of the surface and blistering on contact with molten glass. However, this treatment cannot effectively protect a material containing ZrO in an amount exceeding 10 mass%₂The fused refractory block of (1).

Therefore, there is a need for a fused refractory product comprising more than 10 mass% ZrO₂And has better resistance to molten glass vapor corrosion and lower bleedout.

It is an object of the present invention to at least partially address this need.

Disclosure of Invention

The invention relates to a method for treating a material containing more than 10 mass% ZrO₂The method of fusing a refractory product or "base product" of (a), said method comprising the steps of:

a) heating at least a portion of the surface of the product or "surface to be treated" to cause ZrO in a superficial region extending to a depth of less than 2000 [ mu ] m₂Melting, or "remelting", the grains; and

b) cooling the melted superficial region obtained in the previous step to obtain a protective layer;

c) optionally at least partially recrystallizing the zirconia present in the amorphous phase of the protective layer.

Surprisingly, as will be seen in more detail in the subsequent part of the description, ZrO₂The melting of the grains makes it possible to obtain a very dense and homogeneous protective layer which has excellent resistance to corrosion by glass vapors and a significantly reduced tendency to exude through the treated surface. It cannot be explained theoretically, the inventors also attribute the results obtained (in particular maintaining significant mechanical properties, in particular no cracks) to an extremely low thickness of the protective layer (measured in the depth direction).

The adhesion of the protective layer is also significant.

In a significant way, for containingZrO in excess of 80 mass%₂The fused base product of (2) also achieves this result.

The process described in US 2007/0141348 does not include heating to allow remelting.

The method according to the invention may further comprise one or more of the following optional features:

-in step a), the surface to be treated is heated to a temperature higher than 2500 ℃, preferably higher than 2700 ℃, preferably higher than 2750 ℃, preferably higher than 2800 ℃, preferably higher than 2900 ℃, preferably higher than 3000 ℃;

-in step a), the surface to be treated is irradiated with an incident laser beam or a plasma radiation beam, typically with a plasma torch;

-in step a), heating the surface to be treated, preferably by laser irradiation, to melt the base product to a depth of more than 50 μm, preferably more than 100 μm and/or preferably less than 1500 μm, preferably less than 1200 μm, less than 1000 μm, preferably less than 700 μm, preferably less than 500 μm;

-in step a), feeding more than 50J/mm to the surface to be treated³Preferably more than 100J/mm³Is the ratio of the power per unit area of the beam to the speed of travel of the incident beam on the surface to be treated;

-in step b), cooling the melted superficial region by exposing it to open air;

-in step b), the cooling rate is greater than 100 ℃/s, preferably greater than 500 ℃/s;

the base product is a block, preferably a block having a mass of more than 1kg, preferably more than 5kg, or even more than 10 kg;

the surface to be treated represents more than 10%, more than 30%, more than 60%, more than 80% or even 100% of the surface of one face, or even of the surfaces of a plurality of faces, or even of all faces of the base product;

the product has, before step a), a chemical composition such that:

10％<ZrO₂<98 percent; and/or

0.5％<Al₂O₃<70 percent; and/or

1.5％<SiO₂<40％；

The condition is 90 percent<ZrO₂+Al₂O₃+SiO₂Preferably 95%<ZrO₂+Al₂O₃+SiO₂。

Surprisingly, the inventors have also found that steps a) and b) make it possible to block surface defects or cracks on the base product.

The invention therefore also relates to a method for plugging cavities (e.g. cracks) at the surface of a base product, said method comprising steps a) and b) and optionally c), the surface to be treated comprising said cavities, or even being specifically determined to comprise said cavities.

In one embodiment, the surface to be treated extends continuously from the edge of the cavity by a distance not exceeding 10 mm. Thus, the cavity is treated locally.

The invention also relates to a fused refractory product protected with a protective layer, preferably produced according to the method of the invention, which product contains more than 10 mass% ZrO under the protective layer₂The protective layer:

-contains more than 10 mass% of ZrO₂；

-has a thickness of less than 2000 μm; and

for more than 50% by volume, containing amorphous phases and/or zirconia crystallites (with an average surface area of less than 5 μm)²) Or even consist essentially of an amorphous phase and/or zirconia crystallites.

Melting at high temperature for a limited time makes it possible to obtain this specific combination of microstructure and thickness.

The product according to the invention may also comprise one or more of the following optional features:

preferably, the mean surface area of the zirconia crystallites is less than 2 μm²Or even less than or equal to 1 μm²；

Preferably, the thickness of the protective layer is less than 1500 μm, or even less than 1000 μm;

the porosity of the protective layer, which is the percentage of the surface area occupied by the pores in a section perpendicular to the surface to be treated, is less than 10%, preferably less than 5%, preferably less than 3%, preferably less than 2%, preferably less than 1%. The porosity is preferably measured in a polished section, obtained by scanning microscopy in a section perpendicular to the treated surface.

Definition of

The terms "comprising", "having" and "including" are to be interpreted in a broad, non-limiting sense.

"hot-face" is the face exposed to the interior of the furnace, i.e. the face in contact with the molten material (e.g. glass or metal) and/or with the gaseous environment of the material. The cold side is generally the side opposite the hot side. The hot and cold sides of the block are joined together by:

-a side or "faying surface" facing the side of an adjacent block in the same row of blocks, and

-an upper face facing the lower face of at least one upper block resting on said block and a lower face facing the upper face of at least one lower block on which said block rests.

The thickness of the block is generally its smallest dimension. The distance between the hot side in contact with the atmosphere of the furnace and the opposite cold side is usually measured.

The mean surface area of the zirconia crystallites is the arithmetic mean of the surface areas measured for each crystallite in a section perpendicular to the treated surface. Preferably, an image of the cross-section is taken using a scanning microscope and then analyzed. The area over which the surface area of the crystallites is measured is preferably greater than 100 μm²Preferably more than 500. mu.m²Preferably more than 1000 μm². The magnification is generally adapted to the size of the crystallites to be measured. For example, a magnification of 5000 to 10000 makes it possible to measure the surface area of crystallites, typically 0.1 μm2 to 5 μm 2. The magnification is 10000 to 25000 so that a crystallite surface area of typically 0.01 μm2 to 0.5 μm2 can be measured. Conventional image analysis techniques may be performed, optionally after binarizing the image to improve its contrast.

The porosity is in the vertical directionThe percentage of surface area in the section through the surface to be treated. The vertical cross-sectional profile is arbitrary. Preferably, a cross-sectional image for measuring the surface area occupied by the hole is acquired using a scanning electron microscope. Those skilled in the art know that the surface area of the image used must be sufficient for the measurement to be effective. Preferably, the area of the protective layer on the image has more than 100 μm²Preferably more than 500. mu.m²Preferably more than 1000 μm²To obtain a representative surface area.

More preferably, the sectional image used has the entire thickness of the protective layer.

The surface area occupied by the wells can be measured by conventional image analysis techniques well known to those skilled in the art, optionally after binarization of the image to increase its contrast. Porosity is the percentage of the surface area of the protective layer plus the surface area of the pores present in the image.

The equivalent diameter of the cross section of the bundle is the diameter of a disc having the same area as the cross section.

The term "grains" refers to crystalline elements having a homogeneous or eutectic composition and a size greater than 10 μm.

The term "crystallites" means a surface area of more than 0.1 μm²And less than 10 μm²The surface area is measured on an image taken on a section of the product by an optical microscope.

The term "grain size" refers to the half sum of the total length and the total width of the grains, the length and the width being measured on an image taken by an optical microscope on a section of the product, the width being measured in a direction perpendicular to said length.

The term "mean" means the arithmetic mean.

The term "ZrO₂By "grains" is meant ZrO comprising more than 80%, preferably more than 90%, preferably more than 95%, preferably more than 98%, in mass percent on the basis of the oxides₂The crystal grains of (1).

All percentages relating to the composition are percentages by mass on the basis of the oxides, unless otherwise specified.

Drawings

Other features and advantages of the present invention will become more apparent upon reading the following detailed description and examining the accompanying drawings, in which:

figure 1 shows a cross section of a block treated by laser irradiation according to the invention, in a section perpendicular to the treated surface;

FIG. 2A shows the structure of a block according to comparative example 1, FIG. 2B shows the structure showing non-fused ZrO₂Details of the grains;

FIGS. 3 to 5 show different ZrO according to the invention₂Other pieces of the content, a protective layer was also formed by laser irradiation;

figures 6 and 7 show, on a larger scale, the structure of the zirconia crystallites present in the protective layer of the blocks of figures 4 and 5, respectively, according to the invention;

figures 8A to 8C show a cross section of the block ER1681 and more precisely the structure of the amorphous phase of the protective layer before annealing (figure 8A) and after annealing (figures 8B and 8C), figure 8C showing, by means of high magnification, the appearance of new zirconia crystallites in the protective layer of the annealed block;

fig. 9A to 9C show the appearance of the fused refractory block with cracks before treatment (fig. 9A) and after exposure to the laser beam on the various disk-shaped surfaces (fig. 9B and 9C), fig. 9C showing the blocking of the cracks 20 by means of high magnification.

Fig. 3 to 5 show cracks. They are caused by polishing during the preparation of the polished section.

Detailed Description

Manufacturing method

In step a), the treatment contains more than 10 mass% of ZrO₂A fused refractory product or "base product".

The base product is a dense fused product, i.e. a product having a total porosity of less than 10 vol%, the total porosity being given by the following relation:

total porosity of 100 × (absolute density-apparent density)/absolute density

The apparent density is measured according to standard ISO 5017 on bars taken from the core of the product in healthy areas. Absolute density was measured on the milled powder using a helium pycnometer.

The base product is generally obtained by: the charge consisting of refractory grains is melted, the molten bath thus obtained is cast in a mould and then cooled to solidify the liquid substance. Preferably, the base product is obtained by electric melting.

The base product is typically a fused refractory block.

Preferably, the maximum thickness of the refractory block is greater than 50mm, or even greater than 100 mm. It is noteworthy that the treatment according to the invention does not lead to the occurrence of macro-cracks on the surface of such a block.

The blocks may in particular be selected from the group consisting of plate blocks, burner arches, channel bricks and superstructure parts of glass furnaces.

The surface to be treated is preferably part or all of the hot face of the block (i.e. the surface in contact with the molten glass and/or with the gas extending above the molten glass). In one embodiment, the surface to be treated comprises the entire outer surface of the block.

The base product typically includes an intergranular bonding phase connecting the grains.

The grains comprising ZrO₂Grains and optionally a corundum-zirconia eutectic mixture.

The zirconium in the base product is mainly present in the form of grains. For more than 95%, more than 98%, more than 99% or essentially 100% of its mass, these monocrystalline or polycrystalline grains are preferably composed of ZrO₂And (4) forming.

The average grain size is preferably greater than 10 μm, preferably greater than 20 μm, preferably greater than or equal to 30 μm and/or less than 200 μm, preferably less than 100 μm.

For more than 90% of its mass, the base product preferably consists of one or more oxides selected from the group consisting of: ZrO (ZrO)₂、Al₂O₃、SiO₂、Cr₂O₃、Y₂O₃And CeO₂. Preferably, ZrO₂、Al₂O₃And SiO₂Together account for over 90% of the base product mass.

The base product preferably contains more than 15% ZrO₂More preferably from 26 to 95% ZrO₂。

In various preferred embodiments, the composition of the base product is such that, for a total of more than 90%, more than 95%, or even more than 98%:

-ZrO₂: 26% to 45%;

-Al₂O₃: 40% to 60%;

-SiO₂: 5% to 35%;

or such that:

-ZrO₂: 50% to less than 80%;

-Al₂O₃: 15% to 30%;

-SiO₂: 5% to 15%;

or such that:

-ZrO₂: 80% to 98%;

-Al₂O₃: 5% to 20%;

-SiO₂: 1% to 12%;

or such that:

-10％<ZrO₂≤25％；

-50％<Al₂O₃<75％；

-5％<SiO₂<35％。

the binding phase comprises one or more amorphous or glass ceramic (vitroceramic) phases, preferably silicate phases, and preferably consists of the above. The binder phase preferably constitutes 5 to 50 mass%, preferably 10 to 40 mass% of the base product.

Preferably, said phase is a silicate phase having Na, as a percentage by mass based on the oxides of the silicate phase₂The mass proportion of O is less than 20%, preferably less than 10%, and/or Al of the silicate phase₂O₃Is less than 30 percent.

Preferably, in particular for all these embodiments, Na is present in mass percent based on the oxides of the base product₂O and B₂O₃Is less than 2 percent.

In order to form a protective layer on the surface to be treated of the base product, a large amount of energy is concentrated on a small surface area in a very short time.

Preferably, the base product is initially dry, i.e. it has a moisture percentage of less than or equal to 1%, preferably less than 0.5%, by mass.

The surface to be treated is then irradiated with an incident beam of laser or plasma radiation so as to transmit more than 50J/mm to the surface³Preferably more than 75J/mm³Preferably more than 100J/mm³Or even greater than 150J/mm³And/or less than 500J/mm³、400J/mm³Or 300J/mm³The exposure energy of (a).

The exposure energy is the ratio of the power per unit area of the incident beam to the speed of travel of the incident beam over the surface to be treated. According to ZrO₂Adjusting the exposure energy to the ZrO by the composition of the grains₂The crystal grains are melted. Preferably, the temperature is greater than 2800 ℃.

The power per unit area is the ratio of the power of the incident beam (in watts) divided by the surface area (in mm 2) of the cross-section of the incident beam when it meets the surface or "impingement surface" of the base product.

The power of the incident beam is preferably greater than 10W, 20W, 30W, 40W and/or less than 400W, 300W, 200W, 100W.

The equivalent diameter of the cross section of the incident beam at the impact surface is preferably larger than 10 μm, preferably larger than 20 μm and/or smaller than 100 μm, preferably smaller than 80 μm, 60 μm, 50 μm or 40 μm.

The cross-section of the incident beam can have various shapes, such as a circular cross-section or a rectangular cross-section ("in-line" laser beam). The rectangular cross-section advantageously allows for faster processing of large surface areas. Preferably, the direction of travel of the incident beam is perpendicular to the long side of the rectangular cross-section.

Preferably, the smaller dimension (or "width") of the cross-section of the incident beam on the impact surface is from 10 μm to 500 μm, preferably from 10 μm to 100 μm. Along this width (close to the ZrO at the surface of the fused base product)₂Width of grains) is particularly suitable for obtaining a very dense and uniform protective layer.

Preferably, the beam width is determined according to ZrO present at the surface of the base product₂The average size of the grains varies. Preferably, the larger the average grain size, the larger the beam width. Preferably, the beam width is ZrO₂0.5 to 2 times the average size of the grains.

The power per unit area of the incident beam is preferably greater than 5000W/mm2, preferably greater than 7000W/mm2, preferably greater than 10000W/mm²Or even more than 15000W/mm²And/or preferably less than 50000W/mm²Preferably less than 30000W/mm²Or even less than 25000W/mm²。

The energy supplied to the impact surface must be provided in a very short time to limit superficial damage to the base product and thus the remelting depth. Therefore, the incident beam must travel rapidly.

The speed of travel (in mm/s) of the incident beam on the impact surface with respect to the surface to be treated is preferably greater than 20mm/s, preferably greater than 30mm/s, preferably greater than 40mm/s, preferably greater than 50mm/s, preferably greater than 75mm/s and/or less than 500mm/s, or even less than 300mm/s, or even less than 100 mm/s.

For treating the surface to be treated, preference is given to using a laser, preferably "CO", having a wavelength of 1065. + -.5 nm and an average laser beam power of from 10W to 100W, preferably from 20W to 60W₂A "type laser. The laser device may comprise aiming means which facilitate the positioning of the laser beam. The laser device may be, for example, a laser processor sold by Cerlase.

The incident beam is typically obtained by focusing a primary beam current.

Preferably, the equivalent diameter of the primary beam is less than 1000 microns.

The focal length has an effect on the shape and size of the incident beam. Generally, the shorter the focal length, the higher the power per unit area.

The focal length is preferably 50mm to 500mm, preferably 60mm to 400mm, more preferably 70mm to 300 mm. The focal length is preferably 150mm to 200 mm. Advantageously, the uniformity of the treatment and thus of the protective layer is improved thereby.

Furthermore, such a focal length is advantageously compatible with the above-mentioned laser beam width, and in particular with a width of 10 μm to 100 μm.

A pulsed laser can be used to heat the surface to be treated, which can achieve very high power (power peaks) during the pulses. However, such laser light is emitted only intermittently.

Preferably, the laser used is not pulsed, or is a pulsed laser whose pulse frequency is greater than 300 kHz.

Generally, vectorization represents the edge-to-edge distance between two adjacent lines that are subject to incident beam processing, in microns. If the vectorization is too high or too low, the melting will be less uniform. Vectoring is preferably 0.2 to 2 times, preferably 0.5 to 1.5 times, preferably 20 to 80 microns, preferably 30 to 50 microns of the beam width.

Preferably, the incident beam passes at most once through a region of the surface to be treated.

In step b), the superficial area of the melted base product is rapidly cooled to transform into a protective layer.

By laser treatment, exposure to an ambient atmosphere is sufficient to obtain a quench suitable for obtaining a protective layer.

Additional cooling means may also be used, for example cooling means for blowing air at ambient or lower temperatures.

In step c), the protective layer may be heat treated, preferably by heating,

-preferably, in air,

preferably, at a temperature higher than 1000 ℃, preferably higher than 1300 ℃, preferably higher than 1400 ℃, preferably higher than 1500 ℃,

preferably, the duration is greater than 10 hours, preferably greater than 15 hours, preferably greater than 20 hours,

-the rate of temperature increase is preferably greater than 5 ℃/hour, 10 ℃/hour and/or preferably less than 80 ℃/hour, preferably less than 50 ℃/hour, preferably less than 30 ℃/hour,

-the temperature drop rate is preferably greater than 5 ℃/hour, 10 ℃/hour and/or preferably less than 80 ℃/hour, preferably less than 50 ℃/hour, preferably less than 30 ℃/hour.

Step c) is preferably carried out in air at a temperature ramp rate of 10 c/hour up to 1500 c, held at this temperature for 24 hours, and then controlled down at 50 c/hour.

Therefore, as shown in FIGS. 8A and 8B, ZrO of amorphous phase₂It can be recrystallized in the form of zirconia crystallites. These crystallites preferably have a size of less than 5 μm²、3μm²、2μm²Or even less than 1 μm²And/or greater than 0.1 μm²、0.2μm²Or 0.5 μm²Average surface area of (a).

Treated product

The product obtained by this process is referred to as "treated product". It is composed of substrate and protective layer extended on the surface of substrate.

The substrate is not substantially altered by the method used to make the protective layer. Thus, the features associated with the base product are applicable to the substrate.

The average thickness of the protective layer depends on the nature of the base product, as well as on the parameters of the exposure to the high-energy beam, in particular the power per unit area and the relative speed of travel of the beam with respect to the base product. The average thickness of the protective layer is preferably from 50 μm to 2000 μm, preferably from 100 μm to 1000 μm, more preferably from 100 μm to 700 μm, or even from 100 μm to 500 μm. The average thickness of the protective layer is preferably greater than 200 μm.

The composition of the protective layer is substantially similar to the composition of the substrate and thus also substantially similar to the composition of the base product. Thus, the features relating to the composition of the base product are applicable to the protective layer. In particular, the protective layer preferably contains the elements Zr, Al, Si and O.

Preferably, however, the mass content of the elements Na and/or Si of the protective layer is lower than the mass content of the elements Na and/or Si of the substrate. These elements may actually be volatilized in step a).

In particular, SiO in the protective layer₂Content and SiO in the substrate₂The mass ratio of the contents is preferably less than 1.0, preferably less than 0.9, or even less than 0.8 and/or preferably greater than 0.1, preferably greater than 0.3, preferably greater than 0.5.

The volatilization of the elements Na and/or Si in step a) leads to a relative increase of the other elements. In particular, ZrO in the protective layer₂Content of ZrO in the substrate₂The mass ratio of the contents is preferably greater than 1.0, preferably greater than 1.1, or even greater than 1.2 and/or preferably less than 2.0, preferably less than 1.8, more preferably less than 1.6.

The protective layer may be completely amorphous. The protective layer may also comprise some zirconia crystallites dispersed in an amorphous binder phase. Finally, the protective layer may consist essentially of zirconia crystallites which are practically continuous, to the extent that a substantially continuous phase is formed, in particular when the chemical composition of the base product comprises more than 80% by mass or even more than 90% by mass of ZrO₂Then (c) is performed.

Preferably, for more than 50 vol%, more than 70 vol%, more than 80 vol% or even more than 90 vol%, the protective layer consists of amorphous dense phase and/or zirconia crystallites.

In the protective layer, the zirconia crystallites are preferably single crystals, i.e., crystallites having the same structure as the zirconia single crystals.

Preferably, the zirconia crystallites have an average surface area greater than 0.2 μm²Or even greater than 0.5 μm²And/or preferably less than 5 μm²Preferably less than 3 μm²Preferably less than 2 μm²Preferably less than 1.0 μm²。

The protective layer may further include Al₂O₃Or even crystallites of corundum.

Preferably, for more than 50 vol%, more than 70 vol%, more than 80 vol% or even more than 90 vol%, or even substantially 100 vol%, the protective layer consists of the amorphous dense phase and/orZirconia crystallites and/or containing Al₂O₃The composition of the crystallites of (a).

Preferably, the protective layer comprises more than 80%, more than 90%, more than 95% or even substantially 100% by volume of amorphous phase and zirconia crystallites. This percentage can be evaluated in particular by image processing and by SEM/EDX observation.

Fig. 1 shows that on the surface of a substrate 8 there is a protective layer 10, which protective layer 10 comprises zirconium oxide 12 in amorphous phase form AZS and seeds of some zirconium oxide crystallites 14. Zirconia crystallites 14 can also be seen in fig. 6 and 7.

FIG. 2A shows a superficial attack of the base product, and FIG. 2A particularly shows the presence of unfused ZrO at the surface₂And crystal grains 16.

Fig. 3 to 5 show cracks. They are caused by polishing during the preparation of the polished section.

Examples

The following examples are provided for illustrative purposes only and do not limit the invention.

A base product in the form of a base block having dimensions of 500mm x 500mm is manufactured by a method of melting a starting material in an electric arc furnace and then casting and solidifying in a mold. The dried, dust-free base block is then subjected to the laser beam of a Cerlase processing machine,

the laser beam being "monomodal Yb/CO₂Fiber "type, except for comparative example 2, comparative example 2 used a" YAG fiber Yb-YAG "type laser,

-a wavelength of 1064nm,

the power of the laser beam may be 10W to 100W and the focal distance of the laser beam is adjusted to obtain a uniform protective layer.

The treatment was carried out in a single pass in air at atmospheric pressure, vectorized to 40 μm. The operation of the laser is managed by a control unit directly connected to the fiber laser. The obtained blocks are then observed.

Table 1 shows various laser exposure parameters, as well as measurements and observations on the block after exposure to laser beam radiation.

Observation of blocks

Example 1 according to the invention shows the presence of a dense protective layer (fig. 1).

Analysis of the protective layer by microprobe and Electron Back Scattered Diffraction (EBSD) scanning electron microscopy revealed the absence of Kikuchi (Kikuchi) pattern and hence the presence of substantially pure AZS amorphous phase Al₂O₃-ZrO₂-SiO₂(Al₂O₃: 50 to 51% of ZrO₂: 39 to 41% of SiO₂: 10 to 11 mass percent). Thus, ZrO of the protective layer₂Higher than the base block (and thus higher than the substrate), and the SiO of the protective layer₂The content is much lower.

The presence of some recrystallized zirconia seeds in microcrystalline form, having a surface area of less than 0.01 μm, was also observed²。

The laser-treated block according to example 1 was then annealed in air (step c)), at a temperature increase rate of 10 ℃/hour up to 1500 ℃, held at this temperature for 24 hours, and then controlled temperature was dropped to 10 ℃/hour. Thus, there is a dense amorphous protective layer comprising an average surface area of 0.68 μm²As shown in fig. 8A to 8C.

Comparative example 1 shows that a basic block having the same composition as in example 1 according to the present invention, which does not have a dense and uniform zirconia protective layer even with a low laser travel speed and a high power per unit area, is irradiated at a parameter close to US 2007/0141348.

Is carried out to obtain about 5J/mm³Comparative example 2 of exposure energy (similar to that described in US 2007/0141348), resulting in local melting of the amorphous phase of the bulk without melting ZrO₂The grains (see fig. 2A, and fig. 2B viewed at a higher magnification). This comparative example demonstrates that it is not possible to obtain a protective layer according to the invention on a fused base product with such exposure energy.

Examples 2 to 4 show that it is also possible to have very different ZrO by laser irradiation₂Content (at most almost 95 mass% of ZrO)₂) To obtain a dense and fully attached protective layer. The composition of the protective layer is close to that of the substrate, but the ZrO in the protective layer is comparable to that in the substrate₂Higher content and lower content of silicon dioxide.

Testing

The following bleeding and corrosion tests were performed.

Test 1 Corrosion of glass vapors

Two series of cylindrical test specimens 60mm in diameter and 40mm in length were obtained from the basic block of example 1 (i.e. the non-laser-treated block).

The bottom surface (disk-like) of each cylindrical specimen of the first series is exposed to laser radiation as previously defined. Samples of the second series (control series) were untreated and stored as a control. Each specimen of the two series was then subjected to a corrosion test with sodium sulfate. More specifically, each sample was sealed with high alumina cement into a 50mm diameter platinum crucible containing about 60g of sodium sulfate, in a position where the treated bottom surface (for the first series of samples) or the untreated bottom surface (for the second series of samples) was above and facing the sodium sulfate bath to close the crucible. The assemblies were placed in an oven at a temperature of 1500 ℃ for 100 hours.

The average permeate thickness of the sodium hydroxide was then measured by analysis with an electron microprobe. Table 1 gives the percent reduction in penetration depth of the laser treated first series of samples compared to the penetration depth of the control sample according to the following calculation:

the sodium hydroxide vapor penetration reduction was 100 × (penetration depth of the second control series-penetration depth of the laser treated first series)/(penetration depth of the second control series).

Test 2 exudation

Two series of cylindrical samples 24mm in diameter and 100mm in length were taken from the basic block of example 1 (i.e. the non-laser treated block).

The lower bottom surface and part of the periphery of the first series of samples were exposed to laser radiation. For the periphery, only 2/3, the height of each specimen from its bottom, was therefore processed.

Samples of the second series (control series) were untreated and stored as a control. Each sample of the two series was then placed in a furnace and hung over a platinum crucible with pins to collect the exudate.

The heat treatment is carried out in the furnace via two successive cycles. Each cycle consists of: the temperature was raised to 1550 deg.c, maintained in air at this temperature for 6 hours, and then cooled to ambient temperature. Then, for each sample, the volume percent exuded relative to the initial volume of the sample was calculated. Table 1 gives the percent exudate reduction:

percent exudate reduction was 100 × (volume% exuded sample control series-volume% exuded sample first series)/(volume% exuded control series).

Test 3 Corrosion of molten glass

Two series of cylindrical samples 20mm in diameter and 100mm in length were taken from the basic block of example 4 (i.e. the non-laser treated block).

The lower bottom surface and part of the periphery of the first series of samples were exposed to laser radiation. For the periphery, only 2/3, the height of each specimen from its bottom, was therefore processed.

Samples of the second series (control series) were untreated and stored as a control. The test was then carried out on each of the two series, including the samples that were rotary immersed in a soda lime glass bath maintained at 1500 ℃. The rotation speed around the axis of the sample holder was 6 rpm. Such a speed makes it possible to renew the corrosion interface very frequently, thus making the test more stressed. The test lasted 48 hours.

At the end of this phase, for each sample, the remaining volume of the sample is evaluated, and then the volume loss during the test is evaluated by the difference from the initial volume of the sample. The percentage of volume loss is then calculated by determining the ratio of volume loss to the initial volume.

Table 1 gives the corrosion resistance improvement calculated as follows:

improvement in corrosion resistance was 100 × (volume% loss sample control series-volume% loss sample first series)/(volume% loss control series).

This percentage change measures the improvement in corrosion resistance of the laser treated samples relative to the non-laser treated samples.

a is as follows: comparative examplesTABLE 1

Table 1 shows the significant improvement of the block according to the invention with respect to a comparative block having the same composition.

The corrosion tests carried out in example 4 in contact with molten glass show that even very high ZrO levels can be increased₂The block properties of the contents.

As is now clear, the invention makes it possible to protect ZrO containing more than 10 mass% ZrO₂To provide it with better resistance to molten glass vapor corrosion and lower exudation.

Needless to say, the present invention is not limited to the embodiments described in detail and shown in the drawings provided for illustrative purposes.

Surprisingly, the inventors have also found that steps a) and b) make it possible to block cavities at the surface of the base product, in particular cracks or depressions which may be sites of preferential corrosion.

In one embodiment, the surface to be treated extends continuously (i.e. in an uninterrupted manner) from the edge of the cavity by a distance of no more than 10mm, 5mm or 3 mm. In fig. 9A, the cavity is in the form of a slit 20.

Fig. 9B shows three disc-shaped surfaces 22 to be treated extending along the crack 20.

In one embodiment, the cavity is substantially the center of the surface to be treated.

In one embodiment of the method of the present invention,

-the length of the cavity is at least 1cm or 10% greater than the length of the basic block; and/or

The depth of the cavity is preferably less than 1 cm; and/or

-the width of the cavity is greater than 100 μm and/or less than 1000 μm;

the length and width of the chamber are the length and width of its slot on the surface to be treated.

As shown in fig. 9A and 9B, the cavity is blocked by the same material as that of the protective layer. Thus, the material may comprise one or more of the features of the protective layer.

Advantageously, the plugging does not create any additional defects. The invention thus allows for local repair of the base product.