Application Of DLC Diamond-like Coating On Mechanical Parts

- Jan 05, 2019-

Application of DLC diamond-like coating on mechanical parts


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The surface of mechanical parts need to wear, lubrication, and at the same time make the parts material is generally low temperature tempering carbon steel or alloy steel (tempering temperature below 200 ), which requires the coating when temperature must be controlled under 200 . The diamond-like (DLC) coating prepared by physical vapor deposition is exactly the most ideal choice. Diamond-like coating not only has appropriate hardness (HV1200 ~ 3000), but also has low friction (less than 0.15), and is coated at low temperature. Practice has also proved that this is a very ideal mechanical parts surface protection coating. In particular, the automotive industry will be more important to apply the technology. Because at present, the long-term pressure on the auto industry is to reduce vehicle emissions, and it is expected that in the next few years, the requirements for low emissions will be more stringent. This will lead to a strong promotion of the use of 'new materials' and new processing technologies to increase the efficiency of engines and drivetrains. It is inevitable that policy makers across Europe, Asia and the americas will set new demands for the future of the automobile. Modern vacuum coating technology is one of the key factors to meet the above new requirements. DLC, as the surface treatment of auto parts in the future, will be of great significance for promoting the development of high and new technologies in the automotive industry.


1. Introduction to diamond-like film

DLC film (diamond-likecarbon) is an amorphous carbon film composed of Diamond SP3 hybridization and graphite SP3 hybridization.To put it simply, diamond is formed by the mixture of nano-diamond and carbon, and the proportion of diamond is 20% ~ 80%.A ternary phase consisting of sp3-bonded diamond and sp2-bonded graphite with H (hydrogen).


DLC has a series of properties similar to diamond, such as high hardness, high thermal conductivity, small friction coefficient, corrosion resistance, high broad spectral transmittance, high laser damage threshold resistance, radiation resistance and so on. In essence, diamond-like coating/coating film is equivalent to 'combining diamond and graphite components on the microstructure' to obtain the hardness close to that of diamond material. DLC diamond-like film made of amorphous carbon is much harder than hard metal chloride or carbon-like diamond film made of hydrocarbon, which can only be scratched and worn by natural diamond. Haikola revealed that the amorphous diamond-like coating will wear 1mm when replaced with high-hardness steel under the condition of 1um wear. If diamond-like films are used, most of the wear in modern mechanical structures will be effectively controlled.But the main exception is that the clasp wear of the moving parts has not been solved satisfactorily.Wear and tear of moving parts can be challenging when the lubricant fails to work or stops functioning for other reasons when it is operating at an overload.


Meanwhile, DLC diamond-like coating also has extremely low friction coefficient.Under the condition of dry sliding, compared with the friction coefficient of steel, the friction coefficient is only one-fifth of the corresponding steel value, indicating that this coating can be used as a permanent drying lubricant, not only further reduce wear to improve the life of the workpiece, but also conducive to saving energy consumption.A quantified efficiency figure illustrates the effect: the friction coefficient of a diamond-like coated gear is reduced by 25 to 30 percent compared with that of a normally uncoated steel gear.


Diamond-like coating also has the characteristics of compact arrangement of atomic structure, avoiding the defects of many voids in the internal microstructure of other coatings. In addition to its main component is carbon, amorphous diamond-like has the effect of acid resistance and adsorbent, excellent chemical stability, in the anti-corrosion and prevent material adhesion and other applications have a good effect.


2. Diamond-like film application


Diamond-like features enable it to be widely used in the mechanical parts industry, including the following categories.

(1) precision machinery.Including precision bearings, textile equipment and parts, compressor screws, sliders, pump seals, blades, sewing equipment and parts, springs and precision transmission mechanism.

(2) measuring tools.Including calipers, calipers, plug gauge and fixture, etc.

(3) medical equipment and appliances.These include surgical blades, scissors, heart valves, artificial joints and stents.

(4) internal combustion engine industry.Including fuel injection system (valve tappet, plunger, nozzle), power transmission system (gear, bearing, camshaft), piston parts (piston ring, piston pin) door lock, interior decoration, etc.

(5) entertainment and fitness.Including speaker diaphragm, mobile hard disk, disc, golf clubs bicycle parts and razor blades, etc.

(6) optical.Including infrared anti-reflection film anti-reflection film, glass coating, lens coating acrylic coating and protective film.

(7) decorative coating.Including mobile phone shell, high-end watch indoor and outdoor hardware and sanitary products and accessories.

(8) aerospace.Including aircraft, missile fairing coating, satellite and solar cell coating.


3. Case 1 of diamond-like coating market


At present, the annual demand for automotive coating tappets in China is about 80 million pieces. Each year, schaeffler company holds about 40% of the market share and has the ability to develop and manufacture coating independently.Another 60% of the market, 20% ~ 30%, has been developed and produced by lonbond and HEF. The remaining market is about 25 million pieces per year, which can generate annual sales of over 100 million.


4. Diamond-like coating market case 2


In addition to engine and driveline parts, diamond-like coatings on automotive interiors and multiple body parts can also be beneficial. The decorative coating of various colors on various plastic parts can keep them beautiful throughout their life cycle. Functional coating of exposed parts can be exempted from maintenance. Diamond-like coating on car door locks has been widely used in many high-distribution vehicles of Volkswagen. At present, the coating market in China is about 10 million pieces/year for Volkswagen alone, and the yield of coating is huge.