Fabrication and renovation of electrical contacts

Manufacturers in the ex-Soviet and other countries widely use silver and pseudo-alloys, such as cadmium silver oxide, silver-tungsten, etc., i.e. powder metallurgy products, as material for manufacturing electrical contacts.


Ukraine pioneered worldwide in developing entirely new copper-and-molybdenum-based microcrystalline and micro-layer materials for interrupting contacts.


Such materials are produced by way of high-velocity electron-beam evaporation and subsequent condensation of metallic and non-metallic material in the vacuum environment.


The new materials, now called MDK materials, have been certified and are now produced pursuant to TU U20113410.001-98 Standard. The materials are protected by Ukrainian Patents No. 17204A dated 01 April 1997, No. 34875A dated 15 March 2001 and No. 34875 dated 16 December 2002.


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Microstructure of the contact materials

Typical electrical contacts,
manufactured using materials MDK



The fundamental merits of MDK materials:

- They do not contain silver, hence they cost 2.5...3 times less as compared to electric contract powder materials containing silver.

- In terms of durability, the MDK materials surpass 1.5...2.5 times conventional contact materials.

- They exceed the conventional contact materials in terms of radiation resistance, thermal stability and durability, and they are distinguished by their high heat and electric conductivity.

- The new materials are arching-resistant.

- They substitute completely beryllium bronze.

- They ensure high contact operability and reliability.

- They accommodate the maximum switching current up to1200 A.

- The MDK materials are highly workable in terms of cutting, pressing, grinding and drilling; they are easy to solder by any soldering method with the use of standard silver-containing and non-silver solder.


MDK material cost-efficiency benefits:

Thecost-efficiency of MDK material application is predetermined by three factors:

- contact service life extension;

- contact cost reduction;

- reduction of time expenditure on maintenance of contacts.


The total cost saving where MDK materials are used amounts to 60% … 100%.


The most promising fields of MDK material application are as follows:

- municipal transportation system (contacts used on trams, trolley-buses and underground trains);

- elevator equipment (passenger and freight elevators);

- harbour cranes, shipboard cranes and other load-lifting mechanisms;

- all types of electric fork-lift cars;

- mining equipment;

- industrial and home electric appliances containing relays, starters, contactors, circuit breakers, etc.;

- electrodes for resistance welding machines;

- intercity electric transport (electric locomotives, diesel locomotives, suburban electric trains).


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Serial L-shaped electrical contact
with a pad of MDK

Sliding contacts on the basis:
copper-carbon copper-iron-carbon



For the time being, ELTECHMASH has set up production and produced, in accordance with TU U 31.2-20113410-003-2002 Standard, over 1.6 million electric contacts of 376 types and sizes which are now effectively used in Ukraine, ex-Soviet countries, Czechia and Romania.


There is also an opportunity to renovate contacts by way of replacement of the used contact pad with a new one made of MDK material, thus saving the budget required for purchasing new contacts by 20 to 70%.

ELTECHMASH offers the whole range of contact renovation services. Besides contact pads, renovation of contact holders is also possible. At the customer’s request, any types of electrical contacts may be fabricated or renovated according to technical specifications and/or specimens. 


Physical and Mechanical Properties of MDK Contact Materials as Compared to Ag-W (KMK), Ag-CdO, W-Cu and “Pure” Silver and Copper:

Contact Grade (Composition):

Switching Current, A

Resistivity, µOhm x cm



KMK А10 М (Ag-W) Russia

up to 160



Mallory D-55, PR Mallory&Co. Inc. USA

up to 160



Mallory D-55 W

up to 200



Mallory D-55 F

up to 240



Matthey 20S (W-Ag), England

up to 240



AgCdO 15, "CI  Rau", Germany

up to 250



Dodurit CD015P "Doduko KC1", Germany

up to 280



Elkonite 10W3, (W-Cu) USA

up to 250



Copper MI (GOST 859-78)

up to 250



Silver Cpl (GOST 7221-80)

up to 400




up to 1200




Comparative Assessment of Electrical Contact Physical Properties and Cost


Ultimate Strength, MPa

Ultimate Ductility, MPa

Elongation, %

Conditional Durability

Silver (99.9%)





KMK (Ag-W)










* - the price quoted is indicative and is not an official commercial offer

The peculiarity of contact renovation with the use of MDK material lies in the fact that a renewed contact retains all its functional, physical and operational properties. ELTECHMACH guarantees the same durability of renovated contacts as of new ones.


The Company has developed technologies for manufacturing the following products:


1. Sliding contacts based on such materials as copper-carbon and copper-iron-carbon;

2. Arc-chute contacts based on such materials as copper-chromium and copper-tungsten (Ukrainian Patents No. 32368A dated 15 December 2000, No. 76737 dated 15 September 2006 and No. 86434 dated 27 April 2009).

3. Contact welding electrodes.


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Arc-chute contacts based on copper-chromium

and copper-tungsten material

Contact welding electrodes