Power Generation sector form the backbone of any country in terms of growth and development. This sector has always been under tremendous pressure to provide clean and sustainable energy in the most efficient and cost effective way, acknowledging the fact that the process itself is pretty conventional and a technologically advanced system is required to get the desired output. Few systems which convert the raw form of conventional thermal, wind or fluid energy into power include Steam turbine, Gas turbine, Hydro power etc. However, such power plants suffer from severe high-temperature corrosion and erosion of critical components mainly triggered by aggressive gases like HCl, H2S etc., often in combination with alkali and metal chlorides that are produced during fuel combustion. Ceramic, Carbide and Cermet based Thermal spray coatings play a significant role in improving the performance of components as well as their lifetimes thus significantly increasing the thermal/electrical efficiency of power plants.
A steam turbine is a device that extracts thermal energy from super-heated high velocity pressurized steam and uses it to do mechanical work on a rotating output shaft. In the process blade tips of LP turbine rotor get worn out due to droplet erosion thereby reducing the efficiency of rotor. Also solids contained in dirty steam cause wear on critical components such as rotor and stator blades, sealing areas and other zones subjected to the steam flow. Also the bearing journals of rotors are subjected to sliding wear due to rotation at high RPM. The entire steam turbine system consist of a series of valve component assemblies of which many areas are subjected to severe abrasive, corrosive and erosive wear. Premature failure of any of these components will not only lead to heavy downtime and maintenance costs but also prove to be fatal.
Boiler tubes consist of a series of tubes that contain high pressure flowing water which is heated externally by fire. Boiler tubes are subjected to temperatures which make them more vulnerable to erosion from abrasive soot emitted from burning of coal. Continuous bombardment leads to reduction in wall thickness that eventually leads to failure.
Components coming in contact with steam at high temperatures and subjected to impact loads and erosion can be coated with Chrome Carbide based Cermets like PIC DC12, PIC DC07 etc. and Cobalt super-alloys like PIC C21, PIC C52, PIC C53, PIC C54 etc. These coatings exhibit high temperature oxidation endurance and they prolong the operational life of critical components by enhancing wear and high temperature erosion properties. Carbide coatings are deposited with robotic controlled HP-HVOF process to get uniform coating deposition and further impregnated with special sealant to achieve dense coating. Cobalt based weld overlays are deposited with automated and controlled GTAW and PTAW process. These weld overlays are qualified for WPS, WPQ and PQR as per requirements of BHEL and NTPC. Our coatings find various applications on steam turbine components as listed below :
We have complete in-house capabilities for supply of coated valve components as per customer specification. These components are manufactured to precision on our heavy duty calibrated CNC and Grinding machines. We have successfully supplied completely manufactured valve components for multiple projects through BHEL, NTPC and other multinational OEM’s. Few of these components are listed below :
| Coating Properties | PIC C52 | PIC C53 | PIC DC07 | PIC DC12 |
|---|---|---|---|---|
| Process | GTAW/PTAW | GTAW/PTAW | HVOF | HVOF |
| Bonding | Metallurgical | Metallurgical | Mechanical | Mechanical |
| Micro Hardness (HRc) | 28 - 36 | 42 - 48 | 72 - 74 | 68 - 72 |
| Coating Application | High Temperature Oxidation and Impact Resistance | Erosion and Corrosion Resistance | Erosion and Corrosion Resistance | High Temperature Abrasion and Corrosion Resistance |
| Max Temperature (°C) | < 600 | < 600 | < 700 | < 850 |
| Surface Finish | < 1.6 Ra µm | < 1.6 Ra µm | < 0.8 Ra µm | < 0.8 Ra µm |
We offer ceramic and carbide based coatings on rotor bearing journals to combat sliding wear and corrosion at high operating RPM’s. Our PIC B02 coating deposited with Atmospheric Plasma Spray process and impregnated with special sealer offer good resistance to abrasive and corrosive wear. Our PIC DC09 coating deposited with HP-HVOF process produces very dense and homogeneous coatings and offer excellent resistance to abrasive and sliding wear. These coatings are ground and super-finished to achieve the desired dimensions and surface finish. The coating and grinding process is carried out under controlled conditions and with necessary precautions to ensure that the run-out of journal areas is maintained within 0.01mm.
| Coating Properties | PIC DC09 | PIC B02 |
|---|---|---|
| Process | HVOF | Plasma |
| Bonding | Mechanical | Mechanical |
| Micro Hardness (HRc) | 72 - 74 | 68 - 72 |
| Coating Application | Abrasion and Sliding Wear Resistance | Abrasion and Corrosion Resistance |
| Max Temperature (°C) | < 450 | < 540 |
| Surface Finish | < 0.4 Ra µm | |
We offer TRIBODEX M range of coatings specifically developed for combating erosion in boiler tubes with negligible effect on the heat transfer efficiency of the tubes. TRIBODEX M coatings could extend life of boiler tubes by 3 - 4x in comparison to uncoated tubes. TRIBODEX M range of coatings can be deposited using different processes based on the application requirements.
Gas turbine engines derive their power from burning fuel in a combustion chamber and using the high velocity combustion gases to drive a turbine in much the same way as the high pressure steam drives a steam turbine. One major difference however is that the gas turbine has a second turbine acting as an air compressor mounted on the same shaft. Gas turbines are generally considered the most cost effective and relatively environment-friendly large scale power generation technology, but their capacity as well as their thermal efficiency degrades under high ambient temperature conditions. In order to maintain the thermal efficiency atomized water is sprayed on the axial compressors. Nevertheless the water injection can cause droplet erosion on the first stages of blades of the compressor. Moreover interaction between mating gas turbine components due to vibrations can cause excessive wear and premature replacement. Oxidation at high operating temperature leads to the formation of oxides which is also a major reason for abrasive and corrosive wear and premature failure of components.
Components coming in contact with gas at high temperatures and subjected to impact loads and erosion can be coated with Chrome Carbide based Cermets like PIC DC12, PIC DC07 etc. and Nickel and Cobalt super-alloys like NiCrAlY and CoCrAlY. These coatings exhibit high temperature oxidation endurance and they prolong the operational life of critical components by enhancing wear and high temperature erosion resistant properties. Carbide coatings are deposited with robotic controlled HP-HVOF process to get uniform coating deposition and further impregnated with special sealant to achieve dense coating. Abradables are sprayed with Atmospheric Plasma Spray process for better clearance control & prevent gas leakage. Thermal barrier coatings are also sprayed on Turbine casings and Turbine blades by Atmospheric Plasma Process and sealed with special ceramic sealant to create an impervious barrier resistant to high temperature wear and oxidation. These coatings also help maintain the thermal efficiency of turbine and minimize heat loss.
We offer ceramic and carbide based coatings on rotor bearing journals to combat sliding wear and corrosion at high operating RPM’s. Our PIC B02 coating deposited with Atmospheric Plasma Spray process and impregnated with special sealer offer good resistance to abrasive and corrosive wear. Our PIC DC09 coating deposited with HP-HVOF process produces very dense and homogeneous coatings and offer excellent resistance to abrasive and sliding wear. These coatings are ground and super-finished to achieve the desired dimensions and surface finish. The coating and grinding process is carried out under controlled conditions and with necessary precautions to ensure that the run-out of journal areas is maintained within 0.01mm.
| Coating Properties | PIC DC09 | PIC B02 |
|---|---|---|
| Process | HVOF | Plasma |
| Bonding | Mechanical | Mechanical |
| Micro Hardness (HRc) | 72 - 74 | 68 - 72 |
| Coating Application | Abrasion and Sliding Wear Resistance | Abrasion and Corrosion Resistance |
| Max Temperature (°C) | < 450 | < 540 |
| Surface Finish | < 0.4 Ra µm | |
Hydropower refers to conversion of energy from flowing water into electricity. It is one of the most environmental friendly renewable energy sources with absolutely no carbon or harmful emissions in contrast to burning of fossil fuels in Thermal power stations.
The Hydro turbine is the heart of the power station. Different Hydro turbines such as Pelton, Francis and Kaplan are subjected to high flow rates of water which often contain abrasive sediments and quartz. Constant bombarding of these abrasive particles on the buckets may lead to erosion of base material. This erosion not only leads to reduction in efficiency and operational life of the turbine but also affects day to day operation and maintenance cycles. Removal of turbine for maintenance activities in itself is very difficult, tedious, time consuming and involves lot of additional resources.
Cavitation is also a dominating factor in case of hydro turbines. Low pressure regions of high flow reaction turbines are subjected to heavy cavitation wear. Unplanned stoppages of hydro power plants could lead to heavy operational losses.
These hydro turbines are operated for decades due to which critical sub-assembly parts such as shafts and rings also get worn out. Replacement of these parts tends to be very expensive and time consuming. Other parts which get worn out include guide blades, retainer plates, cones etc.
To increase reliability of these turbines, the components coming in contact with the high pressure water such as buckets, retainer plates, guide blades, cones, etc. are coated with high density and wear resistant HYDREX DC09 coatings that impart high erosion and cavitation endurance. These coatings are deposited with robotic controlled HP-HVOF process to get uniform coating deposition and further impregnated with special sealant to achieve dense coating. Coating properties of HYDREX DC09 is as stated below :
| Coating Properties | HYDREX DC09 |
|---|---|
| Micro Hardness | 1100 - 1400 HV0.3 |
| Porosity | < 0.8% |
| Bond Strength | > 10000 Psi |
| Abrasion Resistance | Excellent |
| Corrosion Resistance | Very Good |
| Max Temperature | < 450°C |
Dimensional restoration of parts such as shafts and rings can be done through Twin Wire Arc Spray process by depositing a range of our WC Alloy materials. To achieve higher wear resistance and optimal coating properties, the base coat is followed by a top coat of superior coating material such as alloy or carbide deposited through Plasma or HP-HVOF process. These coatings are ground to achieve the desired dimensions and tolerances.
