Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/04—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material
  • C23C28/046—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material with at least one amorphous inorganic material layer, e.g. DLC, a-C:H, a-C:Me, the layer being doped or not
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
  • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/04—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material
  • C23C28/048—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material with layers graded in composition or physical properties
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/40—Coatings including alternating layers following a pattern, a periodic or defined repetition
  • C23C28/42—Coatings including alternating layers following a pattern, a periodic or defined repetition characterized by the composition of the alternating layers

Definitions

• the invention relates to a doped diamond-like carbon coating and to a process for depositing such a coating on a substrate.
• Amorphous hydrogenated carbon known as diamond-like carbon (DLC) shows several attractive characteristics. Coatings having a diamond-like carbon composition are suitable as hard, wear resistant, self lubricant and corrosion resistant coatings.
• DLC coatings Another drawback of DLC coatings is that the friction coefficient increases considerably with humidity. This inhibits the application of DLC coatings as low friction coating in humid environment or in water.
• WO98/33948 describes the deposition of a diamond-like nanocomposite
• DLN DLN layer on the substrate before the deposition of a DLC layer.
• DLN coatings comprise generally two interpenetrating networks a-C :H and a- Si:O; and are known as Dylyn ® .
• a silicon-nitrogen doped diamond-like carbon coating comprises the elements C, H, Si and N.
• the concentration ranges of the elements C, Si and N expressed in proportion to the sum of C, Si and N are as follows : 30 to 90 at% C, 5 to 50 at% Si and 5 to 40 at% N.
• the concentration of C is between 40 and 50 at%
• the concentration of Si is between 15 and 40 at%
• the concentration of N is between 12 and 20 at%. It has been shown that the coating can further contain a small amount of oxygen. This presence can be due to diffusion of oxygen into the coating. The amount is however limited to a few percents maximum and is the highest closest to the outer surface of the coating layer.
• the adhesion of the coating according to the invention expressed by means of the critical load, as measured in a scratch test, is greater than 22 N.
• the doped diamond-like carbon coating can be considered as a non- sticking coating.
• a possibility to express the non-sticking behaviour of coatings is by means of their surface energy. In most cases, a low surface energy goes hand in hand with an improvement of the non-sticking characteristics.
• a coating is considered to have non- sticking characteristics if its surface energy is below 40 mN/m. More preferably, the surface energy is below 33 mN/m and most preferably below 30 mN/m.
• the coating is characterised by a high hardness. It has been shown that the hardness is higher than 12
• the hardness is even higher than 15 GPa.
• the coating is very suitable as a coating for a substrate for applications where non-sticking characteristics are desired.
• examples are moulds used for plastic injection moulding, tablet or powder punches and implants such as stents.
• the coating layer can further be doped with one or more additional elements such as fluorine or a transition metal as for example W, Zr or Ti.
• additional elements such as fluorine or a transition metal as for example W, Zr or Ti.
• the presence of metallic doping elements has an influence on the thermal and/or electrical conductivity of the coating. This means that by adding a controlled amount of metallic doping element(s), the thermal and/or electrical conductivity of the coating may be controlled.
• the presence of doping elements can also be desired to control the surface energy.
• an inert gas such as Ar, Kr or Ne can be incorporated into the coating composition, by introducing an inert gas in the vacuum chamber during deposition.
• a multilayered coating is provided.
• This multilayered coating comprises at least one layered structure.
• a layered structure comprises a first layer closest to the substrate comprising a silicon-nitrogen doped diamond-like carbon coating comprising the elements C, H, Si and N; a second layer on the top of the first layer comprising a diamond-like carbon composition; a transition layer between the first and the second layer comprising a mixture of the silicon-nitrogen doped diamond-like carbon coating and the diamond-like carbon composition.
• there is an intermediate layer comprising a mixture of the diamond-like carbon composition layer and the doped diamond-like carbon coating, sandwiched between each pair of consecutive layered structures.
• the transition layer gradually changes from a composition comprising C, H, Si and N to a diamond-like carbon composition layer.
• the intermediate layer gradually changes from a diamond-like carbon composition layer to a composition comprising C, H, Si and N.
• the first layer functions as an excellent adhesion promoting layer for the DLC layer.
• the adhesion promoting layer according to the present invention has the advantage over other adhesion promoting layers, such as silicon layers, that it not only offers a good adhesion, but that it is also characterised by a rather high hardness.
• the multilayered coating has a hardness which comes close to the hardness of a DLC coating layer.
• the repeated alternation of a layer comprising C, H, Si and N and a DLC composition layer allows it to deposit thicker coatings, for example coatings with a thickness of more than 10 ⁇ m.
• the number of layered structures can vary from 1 to 5000 and is for example situated between 5 and 50.
• a multilayered coating according to the present invention shows greatly reduced internal stresses. This is due to the lower Young's modulus (higher elasticity) of the silicon-nitrogen doped diamond-like carbon coating layer sandwiching the DLC coating layer. Even for thick coatings, the total internal stresses of the coating remain low.
• any layer of the multilayered coating can be doped, for example with fluorine or with a transition metal.
• the outer top layer of the coating may be varied.
• the hardness and low-wear characteristics, typical for a DLC type coating prevail. This implies that by depositing a DLC layer on top of a multilayered coating a high wear and abrasion resistance coating is obtained. Thicknesses higher than these of conventional DLC coatings can be deposited in this way. Possible fields of applications are the coating of metal forming tools and textile needles. In the case a doped diamond-like carbon coating comprising the elements C, H, Si and N is deposited on the top, the multilayered coating is characterised by a low surface energy and by a low friction coefficient.
• non-sticking properties of such a coating make it suitable for many applications, in particular as a coating for plastic injections moulds and powder pressing tools.
• outer layer is for example a layer comprising
• a substrate coated with a doped diamond-like carbon coating or with a multilayered coating according to the invention is provided.
• This substrate could be rigid or flexible.
• Possible substrates are hardened steel (e.g. 100Cr-6), aluminium, silicon, titanium or glass.
• a process for coating a substrate at least in part is provided.
• the substrate is brought into the vacuum chamber and is fixed to the substrate plate by any suitable means.
• the surface of the substrate is cleaned before the deposition of the coating.
• This can, for example, be done by bombarding the substrate with ions of an inert gas such as Ar, Kr or Ne. This pretreatment activates the surface and removes residual impurities form the substrate surface.
• a precursor or a mixture of different precursors, comprising the elements C, H, Si and N, is brought into the vacuum chamber, a plasma is formed from the introduced precursor and the composition of the plasma is deposited on the substrate to which a negative bias voltage has been applied.
• the process further comprises the following steps.
• the precursor composition is gradually exchanged by a hydrocarbon without stopping the glow discharge. Subsequently, the plasma is formed from the mixture of the precursor and the hydrocarbon and a transition layer from said mixture is deposited on the substrate to which a negative bias voltage has been applied.
• the mixture gradually changes from a composition comprising the elements C, H, Si and N to a diamond-like carbon composition, comprising only the elements C and H
• the plasma deposition is continued to deposit a diamond-like carbon composition layer from the hydrocarbon until the desired thickness is obtained
• the process further comprises, for each additional layered structure, the steps of gradually exchanging said hydrocarbon by a precursor comprising the elements C, H, Si and N, forming continuously a plasma from the hydrocarbon and said precursor and depositing an intermediate layer from said mixture, - continuing the plasma deposition from the precursor comprising the elements C, H, Si and N, gradually exchanging said precursor by a hydrocarbon, depositing a DLC composition layer from said hydrocarbon
• the plasma may be generated and deposited on the substrate in different ways
• a first possible method to generate a plasma is by means of a capacitivly coupled radiofrequency glow discharge (RF) applied to the substrate
• RF radiofrequency glow discharge
• the frequency is chosen between 1 MHz and 28 MHz, and is preferably
• MF bias voltage 200 to 1200 V
• the frequency of the MF bias voltage can vary between 30 and 1000 kHz
• the plasma is generated by an electron assisted discharge.
• the filament current is preferably between 50 and 150 A, the negative filament bias DC voltage between 50 and 300 V and the plasma current between 0.1 and 20 A.
• a further possibility to generate the plasma is by means of a bipolarly pulsed DC source.
• Bipolarly means that a negative and a positive voltage pulse are applied alternately. Either symmetrical bipolar pulses (equal amplitude for positive and negative pulse) or asymmetric bipolar pulses (amplitude of the voltage during negative pulse higher than the amplitude of the voltage during positive pulse) can be used.
• the magnetic field can be applied by means of an inductive coil.
• the magnetic field is preferably between 10 and 30 Gauss.
• a liquid or gaseous component comprising the elements C, H, Si and N to be deposited in suitable proportions can be used as precursor.
• a preferred precursor is a silazane such as 1 ,1 ,3,3-tetramethyldisilazane or hexamethyldisilazane.
• the precursor can be a mixture of different components, for example a mixture of a silane, a hydrocarbon and nitrogen gas in such a way that the mixture comprises the elements C,
• the hydrocarbon can be a saturated or an unsaturated acyclic or cyclic hydrocabon, with the number of carbon atoms varying from 1 to 20.
• substituted hydrocarbons are suitable as precursor. Examples of precursors are methane, propane, butane, pentane, cyclopentane, ethylene, acetylene and aromatic or substituted aromatic hydrocarbons such as benzene and substituted benzene.
• the pressure in the vacuum chamber is between 1.10 "3 and 1 mbar and preferably between 5.10 "3 and 1.10 "1 mbar, for example 2.10 "2 mbar.
• the flow of the precursor may vary between 0.1 g/hour and 25 g/hour.
• the flow of the precursor is between 1 and 3 g/hour.
• the flow of the inert gas, for example Ar is between 10 and 500 ml/min.
• the precursor and the argon gas are introduced into the vacuum chamber in a controlled way by means of a controlled evaporation and mixing system (CEM).
• CEM controlled evaporation and mixing system
• the CEM system allows it to control the precursor flow as well as the argon flow independently of each other. By the CEM system, the process can be controlled easily.
• the deposition time may be varied according to required thickness.
• FIGURE 1 shows a substrate coated with a silicon-nitrogen doped diamond-like carbon layer.
• FIGURE 2, 3 and 4 show substrates coated with different types of multilayered coatings.
• a substrate 11 is coated with a silicon-nitrogen doped diamond-like carbon coating 12 by means of a RF glow discharge.
• the substrate was brought in the vacuum chamber and was fixed to the substrate plate.
• the surface of the substrate was cleaned by plasma etching the substrate by means of Ar ions during 10 minutes. After the cleaning 1 ,1 ,3,3-tetramethyldisilazane was introduced into the vacuum chamber at a flow rate of 1.8 g/hour, whereas Ar was introduced at a flow rate of 75 ml/min.
• the disilazane precursor and the argon gas were introduced into the vacuum chamber in a controlled way by means of a controlled evaporation and mixing system (CEM).
• a radiofrequency of 13.56 MHz was applied to the substrate plate.
• the bias voltage was 300 V.
• the pressure in the vacuum chamber was 1.6 10 "2 mbar.
• the deposition was carried out during 60 minutes.
• the composition of the coating layer deposited on the substrate is determined by X-ray Photoelectron Spectroscopy (XPS).
• the coating has a carbon content of 43 at%, a silicon content of 40 at% and a nitrogen content of 14 at%.
• the concentration of hydrogen is left out of consideration. It has been shown that a small amount of oxygen, namely 3%, is present.
• the non-sticking properties are evaluated by determining the surface energy of the coating and the contact angle of a water droplet on a coated surface.
• the measurement of the contact angle of a water droplet on the coated substrate gives a contact angle of 81 °.
• the surface energy of the deposited coating equals 30.5 mN/m.
• the dispersive component is 24.9 mN/m, the polar component is 5.8 mN/m.
• the hardness is determined by a nano-indentation test. The penetration depth was 300 nm. By this method the nanohardness is determined to be 15.8 ⁇ 0.4 GPa.
• the adhesion of the coating is determined by carrying out a scratch test.
• the scratch experiments are performed on 4 cm 2 M2 steel plates.
• the coating is characterised by a high elasticity, which is expressed by Young's modulus. This modulus is determined to be 125 ⁇ 2 GPa.
• Si and N as shown in figure 1 is deposited on a substrate by means of an electron assisted DC-discharge in combination with a MF bias applied to the substrate.
• Argon was introduced in the vacuum chamber in order to clean and activate the substrate surface.
• 1 ,1 ,3,3-tetramethyldisilazane was introduced into the vacuum chamber at a flow rate of 7.2 g/hour, while Ar was introduced at a flow rate of 500 ml/min.
• the flow rates are controlled by a CEM system.
• the plasma is generated from a heated filament in combination with a
• the bias voltage on the substrate was 600 V.
• the plasma current was 1 A
• the negative filament bias DC voltage was 100 V.
• the plasma was intensified by applying a magnetic field.
• the magnet current was 5 A.
• the pressure in the vacuum chamber was 8.5 10 "3 mbar.
• the coating layer was deposited during 60 minutes.
• composition of the deposited layer was determined by XPS.
• the composition of the coating is as follows : 45.2 at% C, 15.2 at% N and 39.7 at% Si. These concentrations are expressed in proportion to the sum of C, N and Si.
• the coating comprises 46.0 at% C, 16.1 at% N and 37.9 at% Si, expressed in proportion to the sum of C, N and Si.
• Figure 2 represents a substrate 11 coated with a multilayered coating 13.
• This coating comprises a first layer 14 closest to the substrate comprising C, H, Si and N, and a second DLC composition layer 15. Between the first and the second layer, there is a transition layer 16, gradually changing from a layer comprising the elements C, H, Si and N to a layer with a DLC composition.
• tetramethyldisilazane was introduced in the vacuum chamber at a flow rate of 1.8 g/hour, argon was introduced at a flow rate of 75 ml/hour.
• the bias voltage was 300 V.
• the vacuum chamber there was a pressure of 1.6 10 "2 mbar.
• the first layer was deposited during 30 minutes. After the deposition of the first layer, the 1 ,1 ,3,3-tetramethyldisilazane precursor was gradually exchanged by CH 4 .
• CH 4 was introduced in the vacuum chamber at a flow rate of 80 ml/min, together with H 2 at a flow rate of 20 ml/min.
• the bias voltage was 350 V, the pressure in the vacuum chamber 1 10 "2 mbar.
• the deposition time of the DLC composition layer was 120 minutes.
• the total thickness of the multilayered coating is 2.5 ⁇ m.
• the deposited bilayered coating has a hardness of 21.4 ⁇ 0.7 GPa.
• Young's modulus is determined to be 135 ⁇ 2 GPa .
• the first layer offers the coating an excellent adhesion to the substrate.
• the critical load is considerable increased in comparison with a DLC layer deposited directly on the substrate.
• the bilayered coating is characterised by a high hardness.
• a tetramethyldisilazane precursor is introduced in the vacuum chamber at a flow rate of 7.2 g/hour.
• Argon is added as a carrier gas at a flow rate of 500 ml/min.
• a bias voltage of 500 V is applied to the substrate.
• the plasma current was 1 A, the filament bias 100 V and the magnet current 5 A.
• the pressure in the vacuum chamber was 8.5 10 "3 mbar.
• the first layer is deposited during 30 minutes. Subsequently, the tetramethyldisilazane precursor is exchanged by
• the bilayered coating obtained in this way demonstrates a high hardness (21 GPa). Adhesion measurements by performing a scratch test on a 4 cm 2 M2 steel plate showed a critical load of 28 ⁇ 0.7 N.
• Figure 3 shows a substrate 11 coated with a multilayered coating 13.
• This coating comprises a first layer 14 comprising C, H, Si and N, a second layer 15 comprising a diamond-like carbon composition deposited on the first layer and a third layer 18 with the same composition as the first layer deposited on the top of said second layer.
• a transition layer 16 is situated in between the first and the second layer.
• the first layer closest to the substrate, functions as an adhesion promoting layer.
• the DLC composition layer deposited on this adhesion promoting layer gives the multilayered coating the required hardness.
• the outer layer deposited on the DLC composition layer gives the coating the desired non-sticking properties. Total internal stresses of the coating are low.
• FIG. 4 shows a multilayered coating 13 comprising two layered structures 19.
• Each layered structure comprises closest to the substrate a first coating layer 14 comprising the elements C, H, Si and N, a second DLC composition layer 15 deposited on top of the first layer and a transition layer between said first and second layer.
• first coating layer 14 comprising the elements C, H, Si and N
• second DLC composition layer 15 deposited on top of the first layer
• transition layer between said first and second layer In between the two consecutive layered structures, there is an intermediate bonding layer 17.
• the above described steps could be repeated.

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• Chemical & Material Sciences (AREA)
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• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Vapour Deposition (AREA)
• Other Surface Treatments For Metallic Materials (AREA)

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• 2000
  • 2000-05-16 EP EP00927213A patent/EP1185721A1/de not_active Withdrawn
  • 2000-05-16 JP JP2001501671A patent/JP2003501555A/ja active Pending
  • 2000-05-16 WO PCT/EP2000/004438 patent/WO2000075394A1/en not_active Application Discontinuation
  • 2000-05-16 AU AU45664/00A patent/AU4566400A/en not_active Abandoned

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