CrystalCoat - Good News for Engines Running on Heavy Fuel and Gas
Simplex-Turbulo, agents for Märkisches Werk (MWH), are now able to actively promote a very interesting new product which extends the life of cylinder head valves.
High combustion temperatures in engines operating on HFO combined with fuel impurities are well known to limit the service life of cylinder head valves. Even valves made of expensive nickel-based super-alloys suffer from hot-gas corrosion especially in highly loaded engines.
Since 2004 MWH has been pioneering the development of a solution to these problems. Higher-resistant materials are not easily available, so the approach has been to develop special coatings which protect the valve. Now there are several different grades for the new CrystalCoat, and CrystalCoat HT products. The different specifications allow MWH to tailor the coating to the individual application. All the coatings however include the following characteristics:
• high resistance to hot corrosion
• excellent bonding strength between coating and substrate
• coefficient of thermal expansion matched to the substrate
• elastic and highly resistant to thermal shock
• low porosity
• impermeable and thermodynamically stable up to high temperatures
Hot-gas corrosion tests run at 700o C and 900o C have shown very significant reduction in corrosion rates when compared with Nimonic 80A and Nimonic 81. Operations trials in a 320 mm bore power generation engine have confirmed these results. Trials have so far only been carried out on Nimonic valves coated with CrystalCoat. The next step will be to carry out trials on less expensive valve materials, but already MWH are predicting major savings for operators of engines with high temperatures such as power generating engines, and also on engines operating on gas.