Chemistry: electrical and wave energy – Processes and products – Vacuum arc discharge coating
Reexamination Certificate
2000-02-24
2001-07-17
Nguyen, Nam (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Vacuum arc discharge coating
C427S301000, C427S304000
Reexamination Certificate
active
06261424
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
The present application is the national stage under 35 U.S.C. 371 of PCT/NO98/00158, filed May 28, 1998.
The present invention relates to the field of producing superhard wear-resistant coatings in vacuum, and more specifically to a method of forming a diamond-like carbon coating in vacuum.
The invention may be used to increase the service life of cutting tools, measuring tools, friction assemblies and machine parts as well as in the medicine to improve the biological compatibility of implants, in the electronic engineering to increase the service life of audio and video heads, to improve characteristics of acoustic membranes, as coatings for optical parts, and as decorative coatings.
Known in the art is a method of producing high-hardness diamond-like carbon coatings on metal and dielectric substrates (cf., SU Inventor's Certificate No. 411037, 1975) wherein graphite is cathode-sputtered in a magnetic field at a low pressure of a noble gas, krypton, of 10
−5
to 10
−2
Pa to a cooled substrate having a temperature less than 100 K.
Said process has low productivity due to the low pressure of the processing gas, krypton, and low energetic characteristics of the glow discharge at this pressure. It is technologically difficult to maintain such low temperature of the parts to be treated. One has to complicate the processing equipment significantly to achieve ultrahigh vacuum.
The closest technical solution is a method of forming a diamond-like carbon coating in vacuum, comprising the steps of pretreatment of the surface of a part, placing the part into a vacuum chamber, treating the surface of the part with accelerated ions, applying a sublayer of a material onto the surface of the part, electric arc vacuum sputtering a graphite cathode from a cathode spot and producing a carbon plasma, accelerating an ion component of the carbon plasma, depositing the produced carbon plasma on the surface of the part and producing the diamond-like carbon coating (cf., D. R. McKenzie et al. “Properties of tetrahedral amorphous carbon prepared by vacuum arc deposition,” Journal “Diamond and Related Materials,” 1, 1991, p. 51-59).
In said method the sputtering of the cathode is performed in a stationary discharge from one cathode spot, the carbon plasma is produced, the plasma is separated, that is, cleaned from microparticles being formed in a stationary cathode spot. The ion component of the plasma is electrostatically accelerated by supplying a negative, high-frequency potential, and the diamond-like carbon coating is produced.
In said method the use of the stationary discharge does not permit to obtain the plasma energy necessary to form the diamond like carbon coating, that implies the necessity of additional accelerating the plasma ions by supplying a potential to the part. It results in heating the coating and deterioration of its properties, that is, decreased microhardness.
In addition, there arises a hazard of overheating small-size parts as well as sharp edges, that leads to their softening. If the part is made of a dielectric material the electrostatic acceleration has a small effect.
The stationary electric arc discharge is defined by presence of a movable cathode spot being a source of a low energy carbon plasma as well as a great number of hard graphite fragments escaping from the cathode spot. The ion energy does not exceed 10 to 15 eV. When striking the surface of the part, the graphite fragments considerably deteriorate the quality of the produced coating.
To eliminate this disadvantage, said method uses a curvilinear magnetic deflection system that significantly complicates the method of producing the coating. In addition, the stationary cathode spot being the source of the carbon plasma in said method, produces a narrow carbon plasma beam that does not permit application of a uniform diamond-like carbon coating on elongated parts.
The comparatively small plasma density, that is, the ion concentration implies enhanced requirements to the vacuum level to avoid contamination of the coating with residual gases and respective deterioration of the coating quality. The stationary nature of the process complicates the method of applying the coating because it becomes difficult to maintain the necessary temperature mode. The application of the diamond-like carbon coating onto small-size and film materials involves severe difficulties; in this case the coating properties are unstable.
A foundation of the present invention is the problem of creating a method of forming a diamond-like carbon coating in vacuum, wherein the use of a pulsed arc discharge for generating a plurality of cathode spots at the end surface of the cathode as well as maintaining the temperature of the part by means of changing a pulse repetition frequency will allow to simplify the method of forming the coating, to improve its stability and productivity, and to improve the quality of the formed coating, in particular, its uniformity and wear resistance.
The posed problem is solved by that a method of forming a diamond-like carbon coating in vacuum, comprising the steps of pretreatment of the surface of the part, placing the part into a vacuum chamber, treating the surface of the part with accelerated ions, applying a sublayer of a material onto the treated surface, electric arc vacuum sputtering a graphite cathode from a cathode spot and producing a carbon plasma, accelerating an ion component of the carbon plasma, depositing the produced carbon plasma on the surface of the part and producing the diamond-like carbon coating. According to the invention and in order to produce, accelerate and deposit the carbon plasma, said method comprising the steps of using a pulsed electric arc discharge by which a plurality of cathode spots are excited at the end surface of the graphite cathode, said spots moving along the end surface of the cathode at a velocity of 10 to 30 m/s and generating the carbon plasma having an ion energy of 40 to 100 eV and a concentration of ions in the plasma of 10
12
to 10
14
cm
−3
, with the part being electrically insulated in the vacuum chamber, and maintaining the temperature of the part in the range 200 to 450 K by controlling the discharge pulse repetition frequency.
It is helpful to use metal ions as the accelerated ions in treating a metal part.
It is expedient to use as the sublayer material a metal of thickness 100 to 500 A; used for said purpose was a metal selected from the group consisting of titanium. chromium, molybdenum, zirconium, niobium, tungsten.
It is advantageous to increase the temperature of the part up to a value in the range of 473 to 573 K in treating the surface of the part with the accelerated ions of a metal and then to cool the part to a temperature of 293 to 300 K and to re-treat the surface of the part with accelerated ions of a metal until the temperature reaches 323 K.
It is expedient to perform the method in an argon atmosphere at a pressure of 10
−2
to 10
−1
Pa.
It is helpful to use ions of a gas as the accelerated ions in treating a dielectric part, said gas being selected from the group consisting of argon, nitrogen, oxygen or a mixture thereof.
It is advantageous to apply a sublayer of aluminum nitride of thickness 50 to 200 A to a glass part in treating thereof.
It is expedient to use as the graphite cathode a highly purified graphite wherein the pore amount is about 0.5%.
It is helpful to use as the graphite cathode a graphite with an admixture of a doping element which is an element selected from the group consisting of silicon, germanium, osmium, bismuth, phosphorus, and antimony.
It is advantageous to sputter an additional cathode made of a metal selected from the group consisting of titanium, chromium, aluminiumn, zirconium, silicon, germanium.
It is also helpful to treat the diamond-like carbon coating formed on the part with accelerated ions of a gas or a metal.
The invention will now be described in detail with reference to various specific embodiments thereof.
The method of fo
Goncharenko Valery Pavlovich
Kolpakov Alexander Jakovlevich
Maslov Anatoly Ivanovitch
Browdy and Neimark
Nguyen Nam
Patinor AS
VerSteeg Steven H.
LandOfFree
Method of forming diamond-like carbon coating in vacuum does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of forming diamond-like carbon coating in vacuum, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of forming diamond-like carbon coating in vacuum will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2524508