Plasma Chemical Coating-KEPLA-Coat

Basics

KEPLA-COAT® is a plasma chemical coating that improves aluminium and titanium alloys.

Coating takes place in a saline solution electrolyte. The workpiece is connected in series to an external source of electricity and acts as an anode. During anodization oxygen plasma discharges itself on the workpiece surface and briefly melts the surface thus forming 2 oxide ceramic layers that bond tightly with the outer metallic layer. A barrier layer with a thickness of about 100 nm constitutes the direct bond with the aluminium or titanium workpiece. Then come an oxide ceramic layer with low porosity density followed by one with high porosity density. This layer bond protects the aluminium and titanium against wear and corrosion and, thanks to its surface structure, it allows the absorption of lubricants as well as following workpiece treatments such as, for instance, paintwork or impregnation.
Plasma Chemical Coating-KEPLA-Coat
 

Properties

KEPLA-COAT® layers applied to aluminuim consist of up to 60 percent of corundum. The remaining layer components are mainly Al2O3 and boehmite. Depending on the alloy of the coated workpiece, KEPLA-COAT® can reach a thickness of up to 150 µm. The layer thickness of structural aluminium components usually ranges from 40 to 60 µm. KEPLA-COAT® provides not only excellent wear protection, but also perfect uniform layer, dimensional accuracy and hardness. KEPLA-COAT®-coated substrates show a much greater fatigue strength than substrates with similar layers. These layers can resist aggressive gases such as chlorine and boron trichloride and a layer thickness of 30 μm, for instance, shows a corrosion resistance of more than 3,000 hours in the salt fog test according to DIN EN ISO 9227. In addition, KEPLA-COAT® ensures extremely good anti-friction properties in combination with PTFE or other dry lubricants.
Plasma Chemical Coating-KEPLA-Coat

All technical values published here are subject to the test conditions specified. We therefore empasise that the applications and operating conditions, along with the end user’s practical experience, will ultimately determine the level of performance achieved by the coating and/or coating system.

 

Materials

The KEPLA-COAT® plasma chemical process is well suited for the coating of aluminum and titanium alloys*).
Plasma Chemical Coating-KEPLA-Coat
Formation of a KEPLA-COAT® layer by discharging plasma.
Plasma Chemical Coating-KEPLA-Coat
The photograph shows a metallografic microsection of a KEPLA-COAT® layer on a thread ridge, magnified by 200:1.
Plasma Chemical Coating-KEPLA-Coat
3-D running wheel made of AlZnMgCu0.5 with 50 µm layer of KEPLA-COAT® for expansion turbines and turbo compressors.

The process KEPLA-COAT® white for titanium materials, we have currently not in use. Please contact us regarding a possible project handling.

 

Applications

KEPLA-COAT®-coated aluminum components have a wide variety of applications: for instance, geometrically high-precision rotors in turbo molecular pumps. In this case, the workpiece’s layer without any cracks or pores at all prevents the infiltration of reaction gases and it provides the necessary protection for plasma etching processes while resisting the mechanical stress generated by the extremely high rotation speed.

KEPLA-COAT®-coated aluminum components are used, among other things, as sealing gaskets, fixing discs, cylinders, drums or cylindrical tubes.

  • Aviation and space industry
  • Car industry
  • Communications technology
  • Medical technology
  • Data processing
  • Electronics and optics
  • Vacuum technology
  • Food processing industry
Plasma Chemical Coating-KEPLA-Coat
KEPLA-COAT® treated linear winding drums made of a special aluminum alloy (layer thickness: 50 µm).
Plasma Chemical Coating-KEPLA-Coat
Plasma Chemical Coating-KEPLA-Coat
 

KEPLA-COAT® process variant for titanium-based materials

This KEPLA-COAT® process variant protects titanium-based materials by means of a greyish white oxide ceramic layer with a thickness of up to 50 µm. The layer consists of up to 50 percent of rutile plus anatase and it provides, along with top wear resistance, protection against the spreading of what is known as "titanium fire", namely the self-combustion of the metal at 30 bar and 650°C.
In addition, the corrosion resistance of an as-plated layer of pure titanium with a thickness of 30 µm can persist more than 3,000 hours in the salt fog test as per DIN EN ISO 9227. The electric strength of KEPLA-COAT® amounts to 12 V/µm according to ISO 2376 with a layer adhesion over 30 MPa. With a layer thickness of 30 µm the layer thickness tolerance amounts to ± 5 µm depending on the alloy.
KEPLA-COAT® is well suited for all titanium-based materials and, in particular, pure titanium and TiAl6V4. This coating is used, for instance, for wheels or blades in turbine construction, for valves in racing car engines as well as for helicopter propellers or heat-shields in the aviation and space industry. In addition, KEPLA-COAT® is used in medical engineering for implants and surgical instruments as well as in the optics industry for high-precision instruments in astrophysics and laser technology.
The fatigue limit of the coated workpiece depends on the base material. The coating of titanium-based materials is generally heat resistant to temperatures up to 700°C.
(All technical values published here are subject to the test conditions specified. We therefore empasise that the applications and operating conditions, along with the end user’s practical experience, will ultimately determine the level of performance achieved by the coating and/or coating system.)
 

KEPLA-COAT® black process variant

KEPLA-COAT® black can be used to coat all commonly used aluminium- and titanium-based materials. The usual layer thickness values lie within the 5 to 15 µm range for aluminium-based materials and at 50 µm for titanium-based materials. Owing to the layer’s crystalline structure the base material’s fatigue strength is only slightly affected. KEPLA-COAT® black is suitable, for instance, for optical components, high-precision screw threads or heating radiators. This coating is used in sectors like vacuum technology, microelectronics and the aviation and space industry.
Sealed 10-µm-thick black KEPLA-COAT® layers can withstand a test period of over 1000 h in the salt spray chamber according to DIN EN ISO 9227 / DIN EN ISO 10 289.
An initial roughness of Ra= 0,14 µm is transformed after coating with 10 µm KEPLA-COAT® black into a roughness value of Ra= 0,5 µm.
The outgassing rate of the KEPLA-COAT® black layer amounts to 106 Pa• l • s-1 • cm-2 under specific vacuum conditions with scarce traces of H2O in the residual gas.
KEPLA-COAT® black layers for titanium materials can resist to temperatures up to 700°C.
Layer (Thickness) Degree of absorption α Degree of reflection ρ Colour difference Brightness Emissivity ξ
KEPLA-COAT® black for Al (8 µm) > 95 % ≤ 5 % 29 % 30 % 65 %
KEPLA-COAT® black for Ti (8 µm) > 95 % ≤ 5 % 25 % 15 % 80 %

Remarks :
Absorption coefficient, reflection, colour difference, and brightness were determined at room temperature and within the visible range.
The colour difference indicates the degree of blackness (0 % = theoretically absolute black, 100 % = absolute white).
The emissivity was determined at 85°C and it refers to emissions in the infrared range. (All technical values published here are subject to the test conditions specified. We therefore empasise that the applications and operating conditions, along with the end user’s practical experience, will ultimately determine the level of performance achieved by the coating and/or coating system.)