POLEMA, a powder metallurgy plant, is one of the world's leading manufacturers of products made of chrome, molybdenum, tungsten, metal powders and composites.
At the plant, powder metallurgy is based on the following technology processes: obtaining metals in the form of powders, compacting these powders into products of various shapes using cold and hot isostatic pressing techniques, hydrogen or vacuum sintering, pressure shaping (rolling, forging, extrusion), spraying and flame plating.
Among powder metallurgy enterprises, the company holds leading positions in the international markets of electrolytic refined chrome and sprayed high purity chrome targets, rolled products, molybdenum and tungsten products, high-current contact materials, heavy tungsten alloys. Since 1982, one of the Russia’s largest metal powder manufacturing complexes with the capacity of 3,000 t per year has operated as a constituent of the enterprise.
Established in 1961, POLEMA was acquired by Managing Company “Industrial Metallurgical Holding” in 2004 and successfully fulfils various projects for reconstruction of electrolytic chrome production, mechanical metal-working, production of new materials and expansion of production of base materials made of chrome, molybdenum, tungsten, nickel, nichrome, aluminum titanium compositions and ceramics for physical vapor deposition technologies (PVD), reinforcing, protective, decorative, light-reflecting, resistive, switching and transparent electrically conductive films and coatings.
The volume of production of high-purity chrome sprayed targets and evaporable cathodes reaches 30% of the global market. The company sells its products in the domestic market, China, Taiwan, Korea and covers all key markets of the world in 30 countries: USA, EEC countries, South America and Southeast Asia. It has representative offices in Europe and Southeast Asia.
Modern analytical equipment, including optical emission and mass spectrometers, Leco system instruments, Jeol electron microscope, machines for mechanical testing of metals, etc., guarantees excellent quality control of our products. In production of main types of products, POLEMA uses the ISO 9001:2015 quality management system confirmed by an international certificate.
Aluminum-titanium, chromium, aluminum-chromium sputtering targets, evaporable cathodes
Modern materials for multi-functional hardsurfacing coatings
Our materials for applying hardsurfacing coatings using physical vacuum deposition (PVD) methods are aimed at the synthesis of multi-functional coatings which, along with extreme hardness, boast a low friction coefficient, high tenacity, heat resistance, corrosion resistance, chemical inertness with respect to working material and high resistance to plastic deformation and abrasive wear.
Some Advantages of POLEMA's materials for hardsurfacing coatings:
The materials reflect current trends in the creation of multi-functional hardsurfacing coatings in metalworking, the aviation industry and power engineering.
The coatings make it possible to increase the strength of cutting and stamping instruments exponentially to perform high-speed machining without cooling mediuml, to increase erosion resistance and the endurance strength of machine parts.
A wide selection of compositions makes it possible to control the chemical composition and structure of the coatings, synthesize multi-layer nitride, gradient and nano-structured hardsurfacing coatings for application in various spheres of metalworking, including conditions of cyclical thermo-mechanical stress.
The design of sputtering targets and evaporable cathodes is adapted for various types of vacuum units and various kinds of ion-assisted coating deposition.
All products are made on the basis of customer's specifications. The materials used are characterised by a homogenous microstructure and vacuum tightness.
POLEMA sputtering targets and evaporable cathodes are produced from various Al-Ti, Al-Ti-Si, Cr and Al-Cr compositions
Catalysts
JSC POLEMA produces metallic powders and granules for undeposited catalyzers used in various chemical processes.
Powders and granules from Ni50Al alloy and titanium-promoted NiAl alloy, following aluminum extraction, have high mechanical resistance, stability and selectivity in processes of hydrogenating organic compounds.
Ni-Mn alloy powder, used as a catalyst for synthesizing diamonds, promotes an increase in graphite conversion levels and synthetic diamond size thanks to its thin, lamellar shape.
JSC POLEMA is Russia's largest manufacturer of composite chromium-copper and tungsten-copper materials for high-current contacts in vacuum arc-quenching chambers.
Application
Cr-Cu contacts are used in the vacuum arc-quenching chambers (VACs) of highly dependable, quick-acting vacuum circuit breakers capable of breaking large currents in high-voltage 6-35 kW electrical networks. Contacts are a key element in commutation switches (circuit breakers). Currently, the most common material used in contact pairs in VACs are Cr-Cu composites.
Contacts are subjected to the effects of short-circuit currents and fusing metals in various points of the surface due to the high density of the current in them; as a result, welding joints form in these zones. This problem was one reason that delayed the development of vacuum commutation technology for more than twenty years. The resistance of a VAC's contacts to welding is one of its key characteristics. The problem of welding was solved by developing special contact plates made from chromium-copper composites, which provided a high breaking capacity for circuit breakers in commutation networks, wear-resistance and resistance of contact pairs to welding together.
W-Cu contacts are used in VACs of vacuum contactors with a nominal voltage of 1.14 kW and higher in systems for remote control of electric drivers. The contacts are a long-lasting means of switching contactors in electric circuits on and off and ensure a low cut-off current in the system.
1. Characteristics of fabricated parts from chromium-copper materials
Cr-Cu, W-Cu Contacts
Two types of products are manufactured: disks made from a composite chromium-copper material and complex parts consisting of a contact chromium-copper layer and a copper substratum. High-quality POLEMA-produced electrolytic refined ERC99.95 chromium is used for making these parts. The contact material is distinguished by high purity in terms of gas-forming and metallic impurity content, outstanding physical and mechanical characteristics.
Grades, structure and chemical composition
Grade,
standard Form and structure Chemical composition, mass %
Cr Cu
O max
N max S max
ERCr25Cu75-PM
Single-layer chromium-copper disks
24-27 Base 0.07 0.005 ND
ERCr50Cu50-PM
Single-layer chromium-copper disks
Balance 48-53 0.07 0.005 ND
ERCr35Cu65-PM
Single-layer chromium-copper disks
33-37 Base 0.07 0.005 ND
ERCr30Cu70-PM
Two-layer disks: Cr-Cu and Cu Contact layer 27-33 Balance 0.05 0.005 0.007
Copper layer <1.0 Base 0.02 0.005 0.007
ERCr50Cu50-PM
Contact layer 48-53 Balance 0.05 0.005 0.007
Copper layer <1.0 Base 0.02 0.005 0.007
PM – Powder Metallurgy
Dimensions
Grade Nominal dimensions, mm
Diameter Thickness
Disc Contact layer Copper layer
ERCr25Cu75-PM single-layer discs
90 8.0 to 20.0 -
ERCr50Cu50-PM single-layer discs
48, 56, 66, 70, 80 8.0 to 20.0 -
ERCr35Cu65-PM single-layer discs
42.0 to 90.0 7.0 to 13.0 -
ERCr30Cu70-PM two-layer discs
32 4.0 2±0.5 2±0.5
48, 56, 60, 66, 80 6.0 3±0.5 3±0.5
ERCr50Cu50-PM two-layer discs
32 4.0 2±0.5 2±0.5
48, 56, 60, 66, 80 6.0 3±0.5 3±0.5
At the client's request, contact parts of other dimensions can be produced.
Physical and mechanical characteristics
Grade Minimum
density, g/cm³ Minimum
hardness HB* Minimum
conductivity
%**
ERCr25Cu75-PM single-layer discs
8.2 65.0 55.0
ERCr50Cu50-PM single-layer discs
7.8 90.0 40.0
ERCr35Cu65-PM single-layer discs
8.0 72.0 45.0
ERCr30Cu70-PM two-layer discs
8.35 70 55
ERCr50Cu50-PM two-layer discs
8.35 85 40
* Contact layer Brinell hardness HB 5/250
**Conductivity of the contact layer in % of standard copper.
Other types of contact parts
ERCr30Cu70-PM made from Cr30Cu70 material. Single-layer disks with the dimensions: Ø 50x16, 70x22 mm.
ERCr30Cu70-PM and ERCr50Cu50-PM Bimetallic disks with a contact layer made from Cr30Cu70 or Cr50Cu50 material and copper substrata.
Nominal product dimensions, mm: diameter 48, 56, 66, 80 thickness (height) 10. Thickness of contact layer 4.5±0.5 mm.
Contact parts with other dimensions can be produced at the client's request.
Controlled parameters: chemical composition, dimensions, density, hardness and conductivity.
Sample actual specifications of contact parts
Part Chemical composition, % ρ, g/cm³* HB** σ, %***
Cr Cu O max N max
S
max
ERCr30Cu70-PM
Two-layer disk Ø48x10
Contact layer 30.69 Rem. 0.025 0.002 0.001 8.59 79 59.7
Copper substratum <0.05 Base 0.009 0.002 0.001 - - -
ERCr30Cu70-PM
Two-layer disk Ø56x6
Contact layer 30.16 Rem. 0.026 0.002 0.002 8.54 77.1 58.7
Copper substratum <0.05 Base 0.01 0.002 0.001 - - -
ERCr50Cu50-PM
Two-layer disk Ø66x6
Contact layer 50.3 Rem. 0.042 0.002 0.002 8.4 106 41.1
Copper substratum <0.05 Base 0.008 0.002 0.001 - - -
* ρ - part density
** HB - Contact layer Brinell hardness HB 5/250
*** σ - contact layer conductivity in % of standard copper.
Microstructure
In complex parts, material microstructure is monitored to prevent defects and the thicknesses of the contact layer and substratum are checked, along with the quality of the composite's transition layer.
Sample structures of complex contacts
fig. 1fig. 2
*Fig.1: Complex 2-layer contact material structure ERCr 50Cu50 (fragment). ERCr50Cu50 contact layer and Cu substratum.
*Fig.2: Contact layer structure ERCr30Cu70 (fragment) of bimeitalic contact.
2. Specifications of electric contact parts made from tungsten-copper material
Grade, structure and chemical composition
Contract parts consist of two heterogeneous layers (bimetallic structure): a contact layer made from a tungsten-copper material and a substratum made from copper.
Grade,
standard Part shape and structure Chemical composition, mass %
W Cu O max N max S max
W70Cu30-PM
(elsend) Bimetallic disks made from W70Cu30 + Cu material Contact layer Balance 28-32 0.05 0.005 0.007
Copper layer - Base 0.02 0.005 0.007
PM – Powder Metallurgy
Dimensions
Grade Nominal dimensions, mm
Diameter Thickness
Disc Contact layer Copper layer
W70Cu30-PM 32, 48 4+2.0 2±0.5 2±0.5
Parts with contacts of other sizes can be produced at the client's request.
Physical and mechanical characteristics
Grade Minimum
density, g/cm³ Minimum
hardness HB* Minimum
conductivity,
%**
W70Cu30-PM 11.36 145 55
* Contact layer Brinell hardness HB 5/250
** Contact layer conductivity in % of standard copper.
fig. 3
Sample structure of complex contacts
The parts' material microstructure is monitored to prevent defects. The thicknesses of the layers and the quality of the composite's transitional zone are checked.
*Fig.3: Structure of bimetal contact layer material W70Cu30-PM (fragment).
3. Chromous powdered bronze CuCr2-PM
Parts made of powdered bronze are also used to equip vacuum arc-quenching chambers. They have an increased softening temperature (more than 100 ºC in comparison with cast chromous CuCr0.7 and chromium-zirconia CuCrZr bronzes),and are alloyed with 2% chromium: CuCr2-PM with diameters of 48, 56, 66, 80, et al. Conductivity is at least 85% and hardness at least 115 HB.
Typical specifications:
density 8.86-8.88 g/cm3,
conductivity 87-92%,
hardness 130-140 HB.
Chromous dispersion-reinforced CuCr2-PM bronze in the form of discs with diameters of up to 300 mm are also applied as electrodes for resistance-seam welding of carbon and low-alloyed steels. Electrodes made from thermomechanically treated CuCr2-PM bronze are distinguished from traditional CuCr1 bronze by increased hardness, resistance to setting and service durability under contact sealing.
