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certified by DQS according to EN ISO 9002
Reg. No. 81042-01



HARD CHROME PLATING

Hard chrome coatings have been established for many years as the most reliable and economic solution for the salvage of worn parts, combining high hardness (65HRc) with low co-efficient of friction and fair resistance to corrosion.

The coating is applied on the surface of new metal objects for protection, as well as of worn ones, after proper mechanical treatment (grinding). Thus, dimensional restoration and extended service life of the workpiece is achieved. The coating can be deposited allover the part's surface or just on a specific area (e.g. bearing journals). In case of subsequent grinding, a maximum thickness of 0,4mm can be obtained, whereas, without the need for a final grinding, the maximum permissible thickness is approximately 0,04mm.

Application examples of hard chrome coatings are:

Hydraulic cylinders, printing cylinders, piston rods, cylinder jackets, rolls, tubes, valve spindles, rotor shafts, moulds and draw dies, crankshafts, transmission yokes, engraving rollers, shock absorber rods, pins, housings, etc.

A special application is hard chrome plating of marine diesel engine's (SULZER, MAN B&W, PIELSTICK, MITSUBISHI, etc.), piston crown ring grooves. "METALCHROM" has designed and developed a proprietary system/process of rotational plating of piston crowns that is been granted as a patent (No 1000555/14-2-92, Int. Cl5. C25D 7/04), at the Industrial Property Organization (OBI).


ELECTROLESS/CHEMICAL NICKEL PLATING

Electroless/chemical nickel plating, also called autocatalytic deposition, flourished over the years and had a rapid and exciting growth since its development in the 50's. Especially in the '70s and 80's, electroless nickel became the fastest growing segment of the metal finishing industry.

The coating is deposited by an autocatalytic chemical reduction of nickel ions, without the use of an electric current. As applied, the coating has a microcrystallic, almost amorphous structure, and apart from nickel, contains phosphorous from 7 to 9%. These engineering high-phosphorous coatings show the following properties:

  • Superior chemical and atmospheric corrosion resistance
  • Good wear resistance
  • Natural lubricity
  • Very good coating/substrate adherence

The coating's hardness is 45-50HRc as deposited, with the ability to raise up to 65HRc after proper heat treatment. A great advantage of the electroless plating process, compared to the traditional electrolytic, is overall uniformity of the deposit with no edge build-up, regardless of the shape of the part or surface irregularities.

Chemical nickel coatings can be applied on the surface of most metals and alloys like low or high carbon, stainless, alloy and tool steel, cast iron, brass, aluminum alloys, etc. Typical application examples are:

Plastic extrusion dies and injection molds, abrading plates, spray nozzles, chassis, pins, rods, hydraulic cylinders, blades, electronic card boxes, shafts, etc.


THERMAL SPRAYING

Thermal spray coatings show a continuous development over the years, as several industry sectors put higher standards and require better and more functional coatings with advanced properties.

With thermal s praying, a metallic, ceramic or cermet coating is deposited on the surface of metallic objects with the use of a gun. Molten particles crash onto the substrate, deform and are solidified.

Initially, a bond coating is applied in order to achieve very good adhesion to the substrate, and then the proper final coating is sprayed. The spray raw material is used in the form of wire or powder. Several thermal spraying processes have been developed, depending on the method of heat generation and the atmosphere. The most functional and therefore popular are flame spray, arc spray, plasma spray and HVOF (High Velocity Oxy-Fuel) spray.

METALCHROM performs i) flame spraying, in which heating of particles occurs by combustion of an oxygen-acetylene mixed gas, and ii) arc spraying, in which the heat source is an electric arc.

Thermal spray coatings are applied for the salvage of worn parts and protection against wear, corrosion and high temperature oxidation. They can be deposited at a maximum thickness of 2mm and as opposed to reconditioning by hardfacing, the base metal is not thermally affected.

The process can be carried out at the customer's works in case of very large and heavy parts.

 Application examples of thermal spraying.

A new plasma spraying department is under construction. Plasma spraying offers a wide variety of functional coatings like cermets, ceramics, carbides and others, that provide advanced surface properties such as: thermal conductivity or resistance (thermal barrier coatings), electrical conductivity or resistance, resistance to thermal shocks, excellent resistance to atmospheric or chemical corrosion, erosion, sliding wear, abrasive wear, adhesive wear, fretting wear, molten metals, hardness up to 2500HV


SANDBLASTING - GRINDING - SUPERFINISHING

These treatments are applied on the surface of workpieces before
(preparation) and after (finishing) the coating process, or just on their own, without any subsequent process to take place. After final grinding of the part to the customer's desired dimensions (within given tolerances), the surface can be superfinished to a specified Ra value (min. 0,05µm).


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