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TUFRAM® is a surface treatment method developed to improve the surface properties of aluminium and its alloys. The process combines the properties of hard anodising and coating with polymers resulting in improved properties in a number of aspects:
There are various coatings within the TUFRAM® family, all featuring the combination of properties but each of them optimised to one, or some, of them.
Highest hardness and wear recistance combined with good friction properties.
Good non-stick properties, hardness and wear resistance
Best non-stick properties aspecially against rubber and urethane.
Best dry lubrication by a combination of MoS2 / PTFE coating, together with high hardness and wear resistance.
High hardness and wear resistance.
Best non-stick properties. High hardness and wear resistance, even at higher temperatures.
* The polymers used in the process are approved for the use in food and complies with the following:
FDA CFR21 (subsection 175.300 of section 175 and subsection 177.1550)
Aluminium oxide, which the TUFRAM® coating mainly consists of, is next to diamond the hardest non-synthetic material, in its hardest form, >VHN 2000, and a hardness of well over VHN 1000 in its softer structural form. The hardness in the coating is however lower due to a certain microporosity. Depending on coating thickness and aluminium alloy coated, the hardness varies between VHN 400 and VHN 600.
Schematic illustration of TUFRAM® coating
TUFRAM® coatings provides a much better protection against corrosion than coventional hard anodising. TUFRAM® R66 show little or no effect of corrosion after more than 2000 h Salt Spray Test in accordance with ASTM B117, TUFRAM® L-4 will stand for more than 240 h. TUFRAM® R66 should be used in strong alkaline or acid solutions (pH>9 or pH<3) if there are no efficient inhobitors in the solution or ifthe exposure is at low temperature for a short time. In order to achieve the best corrosion protection pieces to be coated shold have no sharp edges, if possible all radii should be 10x the coating thickness. Also in blind holes, corners and at similar shapes the coating build-up can be disturbed.
TUFRAM® coatings provide exellent friction and slide properties within a wide temperature range. Depending on type continuous use from -200ºC to +450ºC. At higher temperatures decompositions of the polymers in the coating will take place.
At hard anodising the coating is formed by conversion of the surface of the aluminium. As the aluminium on the surface is used for the formations of the coating the dimensional growth is not as big as the coating thickness.
Depending on the aluminium alloy the dimensional growt can vary between 35 and 50% of the coating thickness. Diameter of threads which are coated will increase with approx. twicethe coating thickness. Depending of the hight hardness of the coating, the possibilities to adjust dimensions of threads ans close tolerances on coated parts, are limited.
Chemical compositions of the aluminium alloy to be coated has a great influence on the properties of the coating and on maximum coating thickness. Also the color of the coating is affected by the alloyng elements and the coating thickness. There are no possibilites to dye the coatings. The table below gives some guidance for a proper choice of alloy.
The coating has good adhesion and will not peeloff as it is built up by chemical conversion of thesurface of the substrate material. Due to the high hardness of the coating TUFRAM® -treated parts can stand higher local loads than uncoated aluminium pieces. However, extreme loads can cause cracking of the TUFRAM® coating.
The hardness of the aluminium oxide, of which the hard anodised layer consists is, as above mantioned, much higher than the Vickers hardness, that can be measured in the coating.
Because of this, the TUFRAM® coating shows considerably better resistance against abrasive wear than other materials and coating with much higher hardness. TUFRAM® coatings have better abrasive wear resistance than for instance case hardened steel and hard chromiumcoatings. Best wear resistance is achieved on material with low surface roughness. The figure below shows the difference in taber abraser wear test which is a method for evaluating abrasive wearresistance.
Weight loss per 10.000 cycles at Taber wear test with wheel CS-17 and 1,000g load
To produce the TUFRAM® coating polymers and other organic materials are used to coat and impregnate the hard anodised layer giving it its unique combination of durable dry lubrication and wear resistance. Characteristic of all TUFRAM® coatings is their ability to prevent stick-slip, i.e. the difference between static and dynamic coefficient offriction is very small. The table below shows static cofficient of friction under dry conditions between different TUFRAM® coatings and steel, respectively, to another surface with the same coating.
Coefficient of friction to steel – 0,14
Coefficient of friction to one another – 0,11
Coefficient of friction to steel – 0,15
Coefficient of friction to one another – 0,13
Coefficient of friction to steel – 0,21
Coefficient of friction to one another – 0,19
Coefficient of friction to steel – 0,13
Coefficient of friction to one another – 0,11
Coefficient of friction to steel – 0,30
Coefficient of friction to one another – –
Coefficient of friction to steel – 0,23
Coefficient of friction to one another – 0,18
After running-in and at higher loads TUFRAM® FC-12 has a dynamic coefficent of friction of approx. 0,10 to steel and approx. 0,05 to one another.
At wear situations in which normally adheesive wear appears, TUFRAM® coatings prevent wear even on uncoated mating surface. Pin-on-disc tests have been performed under dry conditions with a steel pin in contact with a TUFRAM® coated disc. In the graph below, the endurance of the dry lubrications is shown for the, in this respect, most interesting TUFRAM® coatings. The graph is showing the number of cycles before coefficient of friction 0,3 is reached vs the load.
In order to be able to meet your expectations of thecoating, we need your help with some information.Yor order and drawings must therefore contain information about:
TUFRAM® opens new doors to your design work and give you possibilities for more cost efficient constructions. TUFRAM® is used in a wide range of applications.
Below a few examples.
Manufacture – Valve body, Cylinder housing Bearing, Motor housing, Transformator body, Shaft, Drying wheel, Cog-wheel, Cylinder, Piston
Vehicle – Brake piston, Valve body, Fork tube, Rotor, belt wheel, Master cylinder
Pumps – Housings, Impellers, Diffuser, Fittings, Lid, Bushing, Piston, Mambrane lid, Slide-valve, Shaft
Plastic – Weld pad, Forming tools, Cores, Feeding screw, Press pad
Packing – Guide, Cylinder, Roll, Forming pad, Pallet, Link, Flap
Food stuff – Frying table, Form, Knife, Baking-plate, Funnel, Scraper,Tube
Defence – Gable, Shield, Magazine lock, Bushing, Locking, Housing, Piston, Igniter holder, Rotor, Housing
Aircraft – Shield, Driving housing, Cog wheel.
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