WO2011041809A1

WO2011041809A1 - Method for producing titanium diboride (tib2) layers from molten electrolytes

Info

Publication number: WO2011041809A1
Application number: PCT/AT2010/000369
Authority: WO
Inventors: Gerhard Nauer
Original assignee: Gerhard Nauer
Priority date: 2009-10-06
Filing date: 2010-10-05
Publication date: 2011-04-14
Also published as: AT508845B1; AT508845A1

Abstract

The invention relates to the electrochemical production of titanium diboride layers from eutectic molten salts in a temperature range of between 500°C and 700°C, by adding tantalum compounds. Electrodeposition occurs when a direct current or a pulsing current is applied in a range of between 1mA/cm² and 200 mA/cm², eutectic mixtures of the salts NaCl, KCl, NaF, KF, LiCl and LiF being used as electrolytes. The addition of tantalum compounds ranges from 0.05 to 10 wt.%. Dense, homogeneous and corrosion resistant layers with thicknesses of up to 50 μm are obtained on different metallic substrates (Fe, Mo).

Description

Patent Application:

Process for the preparation of titanium diboride (TiBi) layers from molten electrolytes

The present invention relates to a method for producing thin, homogeneous, well-adhering layers of titanium diboride on different metal substrates

Electrodeposition of molten electrolytes in a temperature range between 600 ° C and 700 ° C.

Titanium diboride (TiB ₂ ) is excellently suited as a layer for improving the properties of the substrate materials used because of its hardness and its corrosion resistance to different media. Usually, TiB _{2 are applied} by vapor deposition processes, in particular CVD ("chemical vapor deposition") methods on substrate materials such as steel, hard metal or refractory metal.

For the production of layers with thicknesses greater than a few microns is the

Time expenditure for these processes relatively high compared to an electrochemical preparation, which has also been described in detail in the literature.

The disadvantage of the electrochemical processes presented so far in the literature is that in many cases the homogeneity of the layers is insufficient and, moreover, the adhesion to the substrate material appears to be deficient.

The aim of the work was therefore to modify the deposition conditions so that both homogeneity and adhesion of the TiB ₂ layers on different substrate materials are improved.

This is achieved according to the invention in that the base melt electrolyte (e.g.

FLINAK in eutectic composition) in addition to the starting materials for the

^ electrochemical synthesis K ₂ TiFe (potassium hexafluorotitanate) and KBF ₄

In addition, Ta is additionally added, for example, in the form of TaCl ₅ (tantalum pentachloride) in a concentration of the same concentration.

The addition of Ta, on the one hand, results in a significant improvement in homogeneity and, on the other hand, by forming mixtures of TiB ₂ and TaB _2, improved adhesion to the substrate material, as reduced by the difference in the coefficients of thermal expansion between the electrodeposited layer and the substrate material (eg molybdenum) be and are significantly reduced by the layer structure induced by a temperature change stresses in the layer.

Exemplary embodiment 1:

After pre-cleaning the electrolyte components of the FLINAK electrolyte (melting, drying, recrystallization), the salt mixture is prepared in eutectic composition and after addition of K ₂ TiF ₆ (potassium hexafluorotitanate) and KBF ₄

(Potassium tetrafluoroborate) in the ratio 1: 2 again at 600 ° C in a protective gas furnace using a crucible of glassy carbon melted and kept for 12 hours under an argon atmosphere. Addition of 0.5% Ta as TaCls also occurs. The substrate material used is a steel plate with an area of 10 cm ² . Then, for 10 minutes, a current flow of 40 mA / cm ^{2 is} generated between the substrate material and the crucible (connected as counter electrode) via a DC voltage (voltage source, a potentiostat Jaissle 1000 TB). After switching off the flow, the sample is drawn from the electrolyte, washed with water and dried. The thickness of the homogeneously deposited TiB ₂ layer is 22 μιη. The adhesion (tested by means of a pull-off test) is also excellent after thermal cycling, there is no chipping of the layer after testing with steep

Temperature gradient instead.

Embodiment 2:

After pre-cleaning of the electrolyte components (melting, drying, recrystallization), the salts NaCl, NaF and KF in the elektischen ratio at 550 ° C.

fused together and the melt homogenized at 580 ° C for 6 hours under argon inert gas. The addition of K ₂ TiFe (potassium hexafluorotitanate) and KBF ₄

(Potassium tetrafluoroborate) is again in the stoichiometric ratio 1: 2, the amount of Ta is 0.2% and is added as Kaliumheptafluorotantalat. The substrate used is a molybdenum plate of 15 cm ² area. Then it will be on for 15 minutes

Current flow of 60 mA / cm ² between the substrate material and the crucible

(switched as counter-electrode) via a DC voltage (voltage source a potentiostat Jaissle 1000 TB) generated. After switching off the flow, the sample is drawn from the electrolyte, washed with water and dried. The thickness of the homogeneously deposited TiB ₂ layer is 28 μπι.

The adhesion of the homogeneous grown on the Mo substrate layer is unchanged even when tested with steep temperature gradients (change in temperature in the range of 400 ° C / minute) on the Mo substrate high, it could be found no chipping.

This also applies when testing the corrosion properties in liquid metal melts of Al alloys.

Exemplary embodiment 3

After pre-cleaning of the electrolyte components (melting, drying, recrystallization), the salts NaCl, NaF and KF in the eutectic ratio at 550 ° C.

fused together and homogenized the melt at 580 ° C for 6 hours under argon inert gas. The addition of K ₂ TiF 6 (potassium hexafluorotitanate) and KBF ₄

(Potassium tetrafluoroborate) is again in the stoichiometric ratio 1: 2, the amount of Ta is 0.2% and is added as Kaliumheptafluorotantalat. The substrate used is a molybdenum plate of 5 cm ² area. Then, for 20 minutes, a pulsating current flow with a frequency of 100 hertz and a peak current of 40 mA / cm ² between the substrate material and the crucible (switched as

Counter electrode) via a pulsating DC voltage (voltage source a potentiostat Jaissle 1000 Tb in combination with a function generator as a control unit) generated. After switching off the pulsating current, the Mo plate is pulled out of the electrolyte, washed with water and dried. The thickness of the homogeneously deposited TiB ₂ layer is 24 μιη.

The adhesion of the homogeneous grown on the Mo substrate layer is excellent even when tested with steep temperature gradients (change in temperature in the range of 400 ° C / minute) on the Mo substrate, it could be found no chipping.

Exemplary embodiment 4:

After pre-cleaning the electrolyte components of the FLINAK electrolyte (melting, drying, recrystallization), the salt mixture is in elektischer composition

Claims

and after the addition of K ₂ TiF ₆ (potassium hexafluorotitanate) and KBF ₄ (potassium tetrafluoroborate) in the ratio 1: 2 again at 600 ° C in a protective gas furnace using a crucible of glassy carbon melted and held for 12 hours under argon atmosphere. Addition of 1.5% Ta as TaCl ₅ is then also carried out. The substrate material used is a steel plate with an area of 5 cm ² . Then, for 20 minutes, a pulsating current flow with a frequency of 100 Hertz and a peak current of 30 mA / cm ² between the substrate material and the crucible (connected as counter electrode) via a pulsating DC voltage (voltage source a potentiostat Jaissle 1000 TB in combination with a

Function generator). In addition, after every 10th current pulse, an anodic current pulse in the amount of 100 mA / cm ^{2 is applied} to the substrate material. After switching off the flow, the sample is drawn from the electrolyte, washed with water and dried. The thickness of the homogeneously deposited TiB ₂ layer is 12 μπι. The adhesion (tested by means of a pull-off test) is also excellent after thermal cycling, there is no chipping of the layer after testing with steep

Temperature gradient instead.

claims:

1 Process for the electrochemical production of homogeneous and dense layers of titanium diboride (TiB ₂ ) from molten electrolytes with the addition of Ta compounds in

Temperature range between 500 and 700 ° C.

2. The method of claim 1, wherein the electrolytes are eutectic mixtures and at least two salts such as NaCl, KCl, NaF, KF, LiCl and LiF with the addition of soluble in the electrolyte Ta- compounds.

3. The method according to claim 2, according to which the addition of Ta compounds in

Concentration range between 0.05 and 10 wt.% Is.

4. The method of claim 3, wherein a current density for the deposition in the range between 1 mA / cm ² and 200 mA / cm ² is used.

5. The method of claim 3, wherein a pulsating current (frequency range between 1 Hertz and 1000 Hertz) in the range between 1 mA / cm ² and 200 mA / cm ² is used.

6. The method of claim 3, wherein in addition to a pulsating current between 1 mA / cm ² and 200 mA / cm ² short-term between the pulsating cathodic current flow periodically in the range of milliseconds and microseconds, an anodic current is applied.