Using metal wire as the spraying material, through the high-energy density and large current to generate ohmic heating, the metal wire rapidly undergoes solid→liquid→vapor→plasma phase change, resulting in an electric explosion. The explosion shock wave is used to partially melt but not vaporize The metal droplets are sprayed on the surface of the workpiece at a high speed to form a high temperature and ablation resistant coating.
Is that possible for inner coating for oil and gas pipeline if outer diameter 139.7 (5-1/2) and inner diameter 127.3 (5.012)?
Kindly, I hope if I see you answers. I appreciate your advices and guidance for me.
Hi Mohamed,
wire spraying techniques (flame spraying and electric arc metallization) are the oldest thermal spraying technologies invented by Max Ulrich Schoop about 100 years ago. At that time, these were advanced methods of coating, but over 100 years the technique has gone ahead and now there are better technologies. The problem with wire spraying methods is that the coatings are porous, permeable to gases and liquids, and in your case this is completely unacceptable.
Good day, Mohammad. However, such coatings can be applied to metal surfaces. They are porous, but not necessarily gas permeable. As a rule, after applying such a coating, additional machining is required to reduce the roughness. Plasma methods are difficult to apply such coatings to the inner surface of the pipe. You can read about it here
Article On the Problem of Deposition of Wear‐ and Heat‐Resistant Coa...
Article Strength characteristics of coatings in electric-arc metallization
Article Hardness of coatings of various filler materials in electric...
There is an alternative to plasma technologies - flame spraying of coatings. And there is also a journal dedicated to this topic - Journal of Thermal Spray Technology. Perhaps you will find something useful there.
https://www.springer.com/journal/11666
Thanks dear friends and teachers. I appreciate your kindness. But I think the minimum diameter which has it possible to apply the coating by HVOF is about 6 cm by special gun. So, I mentioned diameter(12.7cm) is good to apply the coating by HVOF by commercial gun like JP5000. The best microstructure and performance will be resulted from using HVOF plus powder of superalloy instead of wire. If I want to use wire, I have to apply the coating by wire arc spray. It is possible but weaker than HVOF in the case of performance.
Do you think, is it possible?
Pavel Grinchuk Vadim Verlotski
Dear Mohammed,
such small inner diameters cannot be sprayed with wire, but only with powder. For powder spraying of small inner diameters, there are only three options: flame spraying with a special nozzle, plasma spraying and HVOF using low power devices with a short nozzle (JP5000 is absolutely not suitable). However, no matter how hard you try, it will not work to spray pipes longer than 2-3 meters, and even then at very high investment costs. In addition, in all three cases, the coating will be of poor quality (porous), and the deposition rate will be very low (no more than 10 g/min).
I know of one single technology that allows you to actually get a high-quality nickel alloy coating on the inner surface of a straight steel pipe up to 4-5 meters long and 10-20 cm in diameter.This technology is sometimes used for extruder and looks like this:
Self-fluxing alloy NiCrBSi powder is poured into the steel pipe, after which the pipe is hermetically welded with steel plugs at both ends. After sealing, the pipe is placed in a sintering machine, which rotates it at a speed of several thousand revolutions per minute and simultaneously heats it to a temperature of about 1050-1100°C (melting point of the NiCrBSi alloy). After cooling, a smooth, defect-free coating is obtained with a thickness of 1-2 mm with a hardness of up to 54 HRC and a very high resistance to corrosion.
I am afraid that this technology will be too expensive for your purposes.
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