APPLICATIONS IN THE INDUSTRY
The demands for engineering coatings are becoming more and more stringent. Environmental concerns are also being considered as an integral part of the design process. For future economic competitiveness and a lower environmental impact we must therefore turn our attention to processes that use the minimum of resources. Thermal spraying is an attractive coating technique as it offers a wide choice of materials and processes that have a reduced impact on the environment when compared to conventional plating processes.
Thermal spray coating techniques such as flame spraying, wire arc spraying and plasma spraying, allow many problems of wear, corrosion and thermal degradation to be resolved by engineering the surface with tailor-made coatings.
Compared to traditional surface modification processes, thermal spraying offers greater thickness capability, no part size restrictions, it can be performed in situ, and it produces minimal noxious waste. High processing temperatures allow deposition of many high melting point materials onto a relatively cold substrate.
Growth in thermally applied surface engineering is accelerating. Engineers are constantly seeking to improve performance and add value within commercial restraints. With an increasing number of engineers looking at thermally sprayed solutions, TCPP assists clients to achieve objectives such as :
> Reducing costs
> Improving productivity
> Improving performance
> Improving electrical properties
> Enabling components to operate in higher/lower temperatures
> Enabling components to operate within harsh chemical environments
> Improving efficiency
>Improving life of mating components
> Generating competitive advantage
> Adding value
Many industrial fields are potentially interested by thermal sprayed coatings
> Articles ménagers
> Production d’énergie
> Production des non ferreux
> Production métaux ferreux
> Stockage énergie
Abradable coatings are designed to preferentially abrade when contact is made with a mating part. Thermal spray abradable coatings have low structural integrity so they are readily abraded when they come into contact with a moving surface with higher structural integrity. The coatings are designed not to damage the mating surface.
There are a number of different abradable coatings types, to cater for different operating temperatures, corrosive environments and mating materials. The coating structure can be :
> Very porous with many un-reacted or un-melted particles (which would by normal standards be considered as a very poor coating) produced by very careful selection of spraying parameters to achieve the right degree of abradability. These coatings can be difficult to re-produce accurately and need strict monitoring.
> Dense and uniform structured coatings with additives such as polymers, graphite, bentonite and boron nitride. These additives weaken the matrix material of the coating and can provide some degree of dry lubrication. Abradability is controlled mainly by the concentration of additives and not by changes to the spraying parameters, which aids in providing more consistent coatings.
Derived from aero engine gas turbine compressors, these abradable and rub tolerant coatings are now applied to land based turbines, automotive engine turbo-chargers, pumps and compressors to provide clearance control. These coatings reduce the risk of blade damage and at the same time improve the efficiency and performance of the turbo-charger by managing the rotor path tip clearance.
Abradable clearance control coating applied to rotor path of turbocharger - micro-structure
HVOF applied materials replacing hard chromium
For many years hard chromium has been widely used throughout industry for wear and corrosion resistance with few alternatives available. Chromium offers some wear protection and provides a suitable surface for fluid seals.
The use of hard chromium is now increasingly being questioned due to the environmental impact that the processing chemicals have. These factors are having such an effect that some organizations are banning the use of chrome entirely for new applications. HVOF coatings exceed the wear resistance of Cr plated coatings, whilst not having the same detrimental impact on the environment. Thermally sprayed materials such as Tungsten Carbide offer many advantages over chrome plating, the coatings are much harder, increasing longevity as well as increasing resistance to corrosion. HVOF coatings can be applied quickly and the process lends itself well to high volume production.
Typical applications include : > Hydraulic rams including marine
> Aircraft landing gear
> Rolls used in industries from paper to steel
> Petrochemical applications
> Pump shafts
Wear resistance of various HP HVOF sprayed coatings and hard chrome plate coatings
Temperature resistance of HP HVOF sprayed coatings and hard chrome plate coatings
HVOF spraying of a WC/10Co4Cr coating onto a callendering roll for the paper manufacturing industry. Mirror-like surface finishing improves paper quality and cuts down maintenance costs
TCx is the name of a family of high performances carbide based coatings which are elaborated according, from one hand, the judicious choice between spraying technology and sprayed materials and, on the other hand, good know how in surface finishing.
These coatings exhibit : > high hardness
> high corrosion resistance
> low friction coefficient
> excellent surface finishing
Mechanical properties of TC8 coatings
Micro-structure of TC8 carbide based coating
Bobbin winder rolls with wear resistant surface of isotropic and controlled roughness. Molybdenum and tungsten carbide based coatings.
TC17 carbide based coating on compressor shaft
WC-Ni coating for wear and corrosion protection for plunger rod
WC Co-Cr for chrome plate replacement on 767 landing gear axle
HVOF hard coatings and a new surface finish for ball and gate valves used in the oil and petro-chemical industries and for power generation and marine applications, will set new standards of wear resistance and reliability. The new coatings considerably prolong life and improve performance under aggressive environments and extreme working conditions .
WC 12Co coating on pump shaft
Coatings on aluminium parts
For certain applications in the industry (like for example in the case of very high rotational speeds, machining ability, ... ) it is necessary to work with light alloys like aluminium ones. These alloys are characterized with poor surface properties which induce low resistance to abrasive wear. To overcome these problems deposition of thermal sprayed coating can be achieved.
Grooved roller coated and finished with Alumina or Chrome Oxide
Texturising Rings coated with TCC6 coating
light weight alloy breaking discs coated with for friction and heat resistance
Re-melted self fluxing alloys for shock resistance
Coatings produced self-fluxing alloys are fused metallurgically to bond with the substrate. They form non-pourous protective finishes resistant to abrasion, cavitation, fretting, particle erosion and corrosion at both low and high temperatures to 840ºC. The alloys have boron and silicone constituents which form low-melting fluxes during the contact of the coating material with the surfaces of the part to be coated. Boron and silicone decrease melting temperature of the coating and increase melt liquidity ; solid-state chromium boride and complex carbo-borides provide hardness and wear resistance of the alloys. These advantages enable formation of a high-strength bond on the surface of steel and pig iron tools which bring an excellent shock resistance. Moreover, the ability to calibrate alloy hardness (from 20 to 65 HRC) by mixing various components like carbides attaches a certain degree of versatility to this class of materials.
The self-fluxing alloys can be used for strengthening, protecting and reconditioning parts of oil pumps (plungers), energy sector equipment (tube curves in boilers), vehicles (diesel valves in ships and trains, shafts, pins, etc.), mining and metallurgic industry (shafts, rolls and bars, etc.), extruder cylinders and screws, parts in glass production (cast-iron molds and glass-forming machines), parts of road builders and underground systems and so on .
Using self fluxing alloys is a two step process which results in a dense coating and a metallurgical bond. The first step consists in spraying a high hardness alloy and the second one is re-melting of the coating.
Other applications are also in the section "PRODUCTS AND SERVICES"