The present invention relates to a pre-coated metallic substrate wherein the coating comprising at least one titanate and at least one nanoparticle, said metallic substrate having a reflectance higher or equal to 60% at all wavelengths between 0.5 and 5.0pm; a method for the manufacture of this pre-coated metallic substrate; a method for the manufacture of a coated metallic substrate and a coated metallic substrate. It is particularly well suited for Metallurgy industries.

It is known to use metallic substrate having a high reflectance to produce pieces used in the plants of Metallurgy industries. Indeed, for Example, cooling parts for a pyrometallurgical furnace, cooling rolls, blast furnaces can be made of copper. These pieces are subjected to abrasion, scratching, high temperature, etc. To improve the lifetime of such pieces, it is known to deposit a coating on them.

The patent application EP2785881 discloses a cooling element for a pyrometallurgical furnace such as for a flash smelting furnace or for a flash converting furnace or for a suspension smelting furnace, wherein the cooling element has a fire surface to be in contact with an interior of the metallurgical furnace wherein the cooling element comprises a base element containing copper and a coating at least partly covering the base element, and wherein the coating forms the fire surface of the cooling element, characterized by the coating being at least partly applied by a laser coating process such as laser deposition, and by the coating containing a Ni based alloy.

The patent application also discloses a Method for manufacturing a cooling element for a pyrometallurgical furnace such as for a flash smelting furnace or for a flash converting furnace or for a suspension smelting furnace, wherein the cooling element comprising a base element containing copper and a fire surface to be in contact with an interior of the metallurgical furnace, wherein the method comprising a providing step for providing a base element containing copper, and a coating step for coating the base element with a coating that at least partly covers the base element so that the coating forms the fire surface of the cooling element characterized by applying the coating in the coating step at least partly by a laser coating process such as laser deposition, and by applying in the coating step a coating containing a Ni based alloy.

Nevertheless, when a metallic substrate has a high reflectance, such as copper, there is a loss of energy and therefore of coating thickness. Indeed, to be efficient, the laser should be absorbed by the metallic substrate to modify its surface. If the reflectance of the metallic substrate is high, the laser is mainly reflected leading to a loss of energy, a less modified surface and therefore a coating having a lower thickness.

Thus, there is a need to improve the laser deposition of metallic substrates having a high reflectance. There is also a need to obtain a metallic substrate having a high reflectance being well protected by a thicker coating compared to the prior art.

To this end, the invention relates to a pre-coated metallic substrate according to anyone of claims 1 to 8.

The invention relates to a method for the manufacture of this pre-coated metallic substrate according to anyone of claims 9 to 12.

The invention also relates to a method for the manufacture of a coated metallic substrate according to claims 13 to 16.

The invention relates to a coated metallic substrate according to claims 17 to

20.

Finally, the invention relates to the use of the coated metallic substrate according to claim 21 .

The following term is defined:

- Nanoparticles are particles between 1 and 100 nanometers (nm) in size.

The invention relates to a pre-coated metallic substrate wherein the pre coating comprising at least one titanate and at least one nanoparticle, said bare metallic substrate having a reflectance higher or equal to 60% at all wavelengths between 0.5 and 5.0pm.

Indeed, without willing to be bound by any theory, it is believed that the pre coating mainly modifies the melt pool physics of the subsequent metallic coating and the metallic substrate allowing a thicker coating deposited on its surface. The pre-coating improves the Marangoni flow, which is the mass transfer along an interface between the metallic substrate and the subsequent metallic coating due to a gradient of the surface tension, in Laser metal deposition leading to more penetration which in this case results in more coating penetration depth. It seems that the coating comprises at least one titanate and at least one nanoparticle leads to high deposited metallic substrate and high penetration depth in the metallic substrate.

According to the present invention, the bare metallic substrate has a reflectance higher or equal to 60%, preferably higher or equal to 70%, at all wavelengths between 0.5 and 5.0pm, preferably between 0.5 and 3.0pm and for Example between 0.5 and 1 .5pm. Indeed, without willing to be bound by any theory, it is believed that the reflectance of the metallic substrate depends on the wavelengths of the laser source.

With the pre-coating according to the present invention, it is believed that the metallic substrate is reduced to be below 30%, preferably below 20% at all wavelengths between 0.5 and 5.0pm.

More preferably, the metallic substrate is chosen from copper, aluminum, magnesium, platinum, rhodium, tantalum, silver and gold. Preferably, the metallic substrate does not include iron alloys having above 50wt.% of iron. In particular, the metallic substrate does not include a steel substrate. Indeed, it seems that the reflectance of a steel substrate at all wavelengths between 0.5 and 5.0pm is around 30%.

Preferably, the pre-coating comprises at least one titanate chosen from among: Na2Tb07, K2T1O3, K2T12O5 MgTiCb, SrTiCb, BaTiCb, and CaTiC , FeTiCb and ZnTiCU or a mixture thereof. Indeed, without willing to be bound by any theory, it is believed that these titanates further increase the deposition of the metallic coating and increase the coating penetration depth based on the Marangoni flow.

Preferably, the percentage in weight of at least one titanate is above or equal to 45% and for example of 50 or of 70%.

Preferably, the pre-coating comprises at least nanoparticles is chosen from T1O2, S1O2, Yttria-stabilized zirconia (YSZ), AI2O3, M0O3, CrCb, CeC>2 or a mixture thereof. Indeed, without willing to be bound by any theory, it is believed that these nanoparticles further modify the melt pool physics leading to more efficient material deposition.

Preferably, the percentage in weight of the nanoparticles is below or equal to 80% and preferably between 2 and 40%.

Advantageously, the pre-coating further comprises an organic solvent. Indeed, without willing to be bound by any theory, it is believed that the organic solvent allows for a well dispersed pre-coating. Preferably, the organic solvent is volatile at ambient temperature. For example, the organic solvent is chosen from among: acetone, methanol and ethanol.

Preferably the thickness of the coating is between 10 to 140 pm, more preferably between 30 to 100 pm.

The invention also relates to a method for the manufacture of the pre-coated metallic substrate, comprising the successive following steps:

A. The provision of a metallic substrate according to the present invention,

B. The deposition of the pre-coating according to the present invention,

C. Optionally, the drying of the coated metallic substrate obtained in step B).

Preferably, in step B), the deposition of the pre-coating is performed by spin coating, spray coating, dip coating or brush coating.

Advantageously, in step B), the pre-coating comprises from 1 to 200 g/L of nanoparticles, more preferably between 5 and 75 g.L ¹ .

Preferably, in step B), the pre-coating comprises from 100 to 500 g/L of titanate, more preferably between 175 and 250 g.L ¹ .

When a drying step C) is performed, the drying is performed by blowing air or inert gases at ambient or hot temperature.

Preferably, the drying step C) is not performed when the organic solvent is volatile at ambient temperature. Indeed, it is believed that after the deposition of the coating, the organic solvent evaporates leading to a dried pre-coating on the metallic substrate.

The invention also relates to a method for the manufacture of a coated metallic substrate comprising the following successive steps: I. The provision of the pre-coated metallic substrate according to the present invention and

II. the deposition of at least one metallic coating by laser deposition. Preferably, in step II), the laser deposition is performed with a shielding gas being an inert gas and/or active gas. For example, the inert gas is chosen from helium, neon, argon, krypton, xenon or a mixture thereof. For example, the active gas is chosen from among: CO2, CO, and a mixture of thereof with inert gas.

Preferably, in step II), the power of the laser is between 200 and 17000W and more preferably between 1000 and 4000W.

Preferably, the at least one metallic coating is chosen from among: Inconel, 316L stainless steel, AISI 431 martensitic stainless steel and cobalt-chromium alloys. Indeed, without willing to be bound by any theory, it is believed that this coating improves the corrosion resistance, the abrasion, the starching of the metallic substrate having a reflectance equal or above 60%.

According to the present invention, the laser source has wavelengths between 0.5 and 5.0pm, preferably between 0.5 and 3.0pm and for Example between 0.5 and 1 .5pm.

With the method according to the present invention, a coated metallic substrate is obtained, wherein:

- the bare metallic substrate having a reflectance higher or equal to 60% is coated with at least one metallic coating,

- the melted pre-coating is present at the interface between the metallic substrate and the at least metallic coating and

- the bare metallic substrate comprising dissolved and/or precipitated pre-coating. It is believed that this coated metallic substrate has a thicker metallic coating and therefore a higher protection thanks to the pre-coating compared to prior art.

Preferably, the at least one metallic coating has a thickness between 0.3 and 10mm and more preferably between 1 and 8mm.

Preferably, the metallic substrate is coated with at least two layers of metallic coatings. Advantageously, the metallic substrate comprises dissolved and/or precipitated titanate and nanoparticles. Indeed, it seems that during the laser deposition, at least a part of titanate and nanoparticles are present in the metallic substrate.

Finally, the invention relates to the use of the coated metallic substrate according to the present invention for the manufacture of a cooling part for a pyrometallurgical furnace, cooling rolls, blast furnace.

With a view to highlighting the enhanced performance obtained through using the pre-coated metallic substrate according to the invention, some concrete examples of embodiments will be detailed.

Examples

For the Trials, the copper substrates having the chemical composition in weight percent in the following Table 1 were used:

1 .064pm. These wavelengths are commonly used in laser sources in laser metal deposition.

An acetone solution comprising MgTiC>3 (diameter: 2pm), S1O2 (diameter: 10nm) and T1O2 (diameter: 50nm) was prepared by mixing acetone with said elements. In the acetone solution, the concentration of MgTiC>3 was of 175 g.L ¹ .

The concentration of S1O2 was of 25g.L T The concentration of T1O2 was of 50 g.L 1

Then, Trial 1 was coated with the acetone solution by spraying. Trial 2 was not coated with this solution.

Then, a metallic coating comprising 2 layers of Inconel 625 was deposited on Trials 1 and 2 by laser metal deposition. The chemical composition in weight percent of the Inconel 625 is in the following Table 2:

The first ayer was deposited with a laser power of 3.8kW. The second was deposited with a laser power of 1 2kW. The carrier gas was Argon. After the deposition of Inconel 625 on Trials 1 and 2, the thickness of the layers and the depth of the coating penetration in the copper substrate were measured by Scanning Electron Microscope (SEM). Trials were bended until 180° according to the norm ISO 15614-7. Results are in the following Table 3:

*: according to the present invention

The thickness for the Inconel 625 metallic coating is thicker with Trial 1 than Trial 2. Moreover, the depth of the coating penetration is higher with Trial 1 than 2. Indeed, the reflectance of Trial 1 has been decreased leading to an improvement of the laser deposition.

Then, the hardness of both T rials was determined across the metallic coating and the copper substrate using a microhardness tester a represents the hardness of the second layer of coating; b represents the hardness of the first layer of coating; c represents the hardness at the interface between copper substrate and the first layer of coating and d represents the hardness of the copper substrate. Results are in the following Table 4:

^* : according to the present invention

The hardness value of Trial 1 is more homogeneous across the metallic coating than Trial 2 where a softening interface is observed.