Nedox – UK

NEDOX® is a surface treatment method to be used on steel, stainless steel, cast iron, copper and copper alloys. The process combines the properties of electroless nickel and coating with fluorocarbons resulting in a number of improved properties:

High Hardness
High wear resistance
High corrosion resistance
non galling properties
Low cofficient of friction
Non-stick properties
Close dimensions
Uniform coating/
No post machining

There are variorus coating withhin the NEDOX® family, all featuring the combiination of properties but each of them optimised to one, or some, of them:

NEDOX® SF-2*

Highest hardness and wear resistance in combination with best corrosion resistence, low coefficient of friction and non-stick properties, Approved for use in contact with fod and drugs.

NEDOX® NH-1

Good corrosion resistance, hardness and wear resistance in combination with low coefficient of friction.

NEDOX® NH-3

High hardness and wear resistance in combination with low coefficient of friction.

NEDOX® U-4*

Best non-stick properties, especially against rubber and urethane, and at heat welding of plastics. Approved for use in contact with food and drugs.

NEDOX® FM-5

Best dry lubrication, lowest cofficient of friction, by a combination of MoS2 / PTEE Together with high hardness and wear resistance.

* The flourocarbons used in the process are approved for the use in food and drug industry by the US Food & Drug Administration and the USDA.

Basic coating build-up for the NEDOX® coating is an electroless nickel coating process. The term “electroless process” is used to describe methods of plating by means of chemical reduction instead of using current as in electroplating. The reducing agent used is sodium hypophosphite which results in a conntent of 9-12% of phosphorus in the produced coatings. This gives the coating a number of intersting properties. By combining thes with different types of treatment with flourocarbons NEDOX® coatings ends up with additional improved properties and positive synergistic effects.

HARDNESS

The electroless nickel coating is a supersaturated solid solution of phosphorous in nickel resulting in stresses in the lattice and increased hardness in the coating. Hardness at plated is -580 HV 0,05. By heat-treatment of the coating, nickel phosphide, Ni3P which is very hard, precipitates resulting in increased hardness and wear resistance.

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NEDOX® coating´s hardness and wear resistance vs heat-treatment temperature.

Maximum hardness possible to achieve is -1000HV 0,05. NEDOX® SF-2 and U 4 are heattreated to maximum hardness of the electroless nickel coating. In NEDOX® NH-1 the hardness is -580 HV 0,05 and in NEDOX® NH-3 -800 HV 0,05. -580 HV 0,05 and in NEDOX® NH-3 -800 HV 0,05.

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Hardness at elevated temperatures in NEDOX® and hard chromium coatings.

The hardness in the NEDOX® coatings is not reduced, as in hard chromium coatings, until the working temperature exceeds ~350ºC.

Wear resistance

The wear resistance against abrasive wear is for homogenous materials proportional to the hardness of the material. The wear resistance of not heat-treated NEDOX® coatings are equal to steel with low carbon content with the same hardness. Steel with higher carbon content and equal hardness has better wear resitance as they have a larger amount of hard carbides wich strongly contributes to an improved wear resistance. equivalent to that the hard nickel phosphides that are precipitated in the NEDOX® coatings at heat treatment contributes more to improved wear resistance than to higher hardness in the coating. NEDOX®SF-2 has better resistance against dry abrasive wear than hardened steel and is combarable with hard chromium coating and Tuff Trided steel. The wear resistance of NEDOX® NH-3 is combarable with steel hardened to 62 HRC and NEDOX® NH-1`s is better than ordinary low alloyed steel. The best wear resistance is achieved on material with low surface roughness, Rz 4 µm.

Sliding properties

The combination of the electroless nickel coating, the fluorocarbons and other organic materials are synerdistic and together they give the NEDOX® coatings their unique combination of durable dry lubrication and high wear resistance. NEDOX® coatings lowers stick-slip effects in unlubricated contacts (the difference between static and dynamic coefficient of frictions is wery small) and offer a guarantee for safe function in applications with intermittent movements. The wear index of NEDOX® SF-2 at dry sliding contact is:

– against steel 03 * 10-14 m 2/N

– against NEDOX® SF-2 03 * 10-15 m 2/N

Also in oil lubricated applications working at lower sliding speed the NEDOX® cooatings reduces friction and wear.

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* Case hardening steel SS2511, ground surfaces

** Oil for pneumatic tools, Nynäs LB31

Coefficient of friction between different material couples in pin-on-disc test. Sliding speed 1 m/s, contact pressure 45 MPa.

Also characteristic of the NEDOX® coatings are their anti-galling properties at very short and high loadings. Comparative oil lubricated galling test where NEDOX® SF-2 has been compared with case hardened and carbonitrided sreel has been performed. In the test, the load is put on very quickly and held at the surface pressure during 0,1-1,0 s. In tests where both surface have been coated with NEDOX® SF-2.

Non of them have shown any galling though the force has exceeded the yield strength of the substrate. In the graph below the level at which galling appears at differend sliding speeds have been plotted for the different materials.

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Results of galling test with materials with different types of surface treatment´s, pin Ø3,0mm against disc, lubricated with oil Nynäs LB31

Corrosion resistance

NEDOX® coatings show very good corrosion resistance. The fluorocarbons are chemically fully inert in almost all environments and electroless nickel shows excellent corrosion resistance due to its passive surface.

In order to achieve best corrosion protection with as thin coating as possible of NEDOX® NH-1, which has no completely tight cover of flourocarban coating, it is important than the substrate has a smooth, clean and pore-free surface. Non-metallic inclusions in the surface of the substrate material, carbides, sulphides etc. emanating from alloying elements or impurities, as well as a porous or rough surface can breed pores in the coating resulting in less corrosion protection. Corrosion speed of the coating is though in general very low in most environment as shown in table beside.

The organic coating on NEDOX® SF-2 covers the nickelcoating better and is therefore not affected to the same debree by the above. Corrosion protection properties of NEDOX® U 4 is only decreased by a very high and sharp surface roughness and sharp edges which can penetrate the organic layer and by larger pores in the substrate from which process liquids can bleed out and damage the coating.

Required coating thickness varies of course with environment severity as well as above mentioned interference from base material.

In Salt Spray Test in accordance with ASTM B117 test panels of liw alloyed steel with surface roughness Rz -4 µm coated with 40 µm NEDOX® SF-2 or U 4 stand more then 2000 h without showing any effect of corrosion. 40 um NEDOX® NH-1 or FM-5 stand 1200 h in the sane test.

Temperature range

NEDOX® SF-2, NH-1, NH-3 and U 4 do withstand continuous use from -200to+350ºC. At higher temperatures decompositions of the flourocarbons will take please. NEDOX® FM-5 is designed to be used between -50 and +260ºC. At higher temperatures the endurance of the dry lubrication properties will decrease.

Coating thickness dimensional changes

In order to meet the demands regarding corrosion and wear resistance with the NEDOX® coatings in different applications the folowing coating thickness are recommended:

– mild exposure* 5 to 10 µm

– moderate exposure 10 to 25 µm

– severe exposure 25 to 50 µm

– very severe exposure more than 50 µm

*minimum 10 um is wear applications

In design of components to be NEDOX® coated it is important to consider the dimensional change due to the coating. all surface that are coated get a dimensional increase equal to the coating thickness. Diameter diamensions of threadedparts or splines get a dimensional change of:

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This means that a screw with 60º top angle of the treads coated with 25 µm get an increase in diameter of 0,1 mm

Goods, type and size

NEDOX® NH-1 and NH-3 are available as both rack and barrel plating. Other NEDOX® processes are only available as rack plating. Maximum good size is 1 * w * h: 1100 * 550 * 800mm.

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* Can produce dark discoloration, **at 95°C, ***at 100°C.
Corrosion speed on NEDOX®NH-1 in liquids at 20°C

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Specification at order

In order to be able to meet your expectations of the coating, we need your help with some information. Your order and drawings must therefore contain informations about: Customer name

Reference name

delivery address

Means of transportation

Product name

Product number

Number of pieces

Coating method

Coating thickness

Tolerances

Maskin off, in any

Critical surfaces

Surfaces for contacts (jig marks)

Type of alloy

Hardness

Examples of applications

NEDOX® opens new doors to your design work and gives you possibilities for more cost efficient constructions NEDOX® is used in a wide range of applications. Below a few examples.

Manufacture

Bushing, guide, piston, bolt, brake bolt, drying drum, saw blade, nipple, lock part, Wear washer, shaft

Vehicle

Diffuser, impeller, pump shaft, lid, pump housing, pump screw, cog wheel, piston

Pumps

Core, pusher, forming tool, dissemler pad, forming case

Plastic

Groove, sliding rail, heat sliding rail, welding pad, roll, cylinder, funnel

Packing

Own grid, frying table, scraper, knives

Food stuff

Rotor case, case, igniter, housing

Defence

Bolt

Aircraft