ABSTRACT
High temperature corrosion and erosion of the boiler pipes has been becoming one of major issues which puzzled security and stability of power plant for generations. Especially in recent years, with development of industrial and the increasing of power consumption, the larger capacity generators emerged. At the same time, the low quality coal was used to reduce the cost of power generation, which result the corrosion speed of the pipeline greatly increased. In order to improve the power plant boiler pipe the capability of corrosion-resistant, an ti-erosion at high temperature. Preparing FeCoCr coatings on the surface of 20 steel used the supersonic electric arc thermal spraying technology. The high temperature oxidation, vulcanization and wearing of coatings were tested. Metallographic microscope, X -ray diffraction, scanning electron microscope and micro hardness tester etc were used to test and analysis .
Draw the following conclusions:
(1) The supersonic electric arc spraying FeCoCr coatings were obvious layer structure, the thickness was about 230 ji in and the organization was dense.The pore rate of coatings was about 5%. The coating is mainly composed of metal compounds of CoFe, (Cr, Fe) and a little of Si02.
(2) The bond strength of FeCoCr coatings and the substrate is about 19MPa.Heated and air-cooled at 700。C for 600 times, there were no significant spalling and cracks in the coatings, indicating that the coatings' property of thermal-shock resistance was well and coatings matched with the substrate material well.
(3) Samples oxidized at 700°C for 100 hours, substrate weight gained of 20 steel was about 230}ig/mm and FeCoCr coatings was about 60[ig/mra". The weight gained of the 20 steel as more than 3 times as the FeCoCr coatings specimen. The high temperature oxidation resistance of 20 steel was improved obviously by FeCoCr coatings. It benefits from the dense Cr203 and CoO oxidized film on the surface of coatings. So the way of oxidation gradually transformed into the mass transfer reactions from the initial interface reaction and corrosion was decelerated. The substrate of 20 steel has been interface reaction, so corrosion faster.
(4) Samples vulcanized at 700°C for 100 hours, 700 °C heat curing 100 hours, substrate weight gained of 20 steel was about 1400p.g/mm and FeCoCr coatings was about 400|ig/mm". The weight gained of the 20 steel as more than 3 times as the FeCoCr coatings specimen. The high temperature vulcanization resistance of 20 steel was improved obviously by FeCoCr coatings. It benefits from the dense CoCr204, CoFe204 and Cr203 oxide film on the surface of coatings. They protected the internal metal.
(5)The coating micro-hardness was about 615N/mm2. The friction coefficient of FeCoCr coatings was about 0.33 heated at 700"Cfor 100 hours.The friction coefficient without heat treatment was about 0.4. The friction coefficients of the substrate of 20 steel always were approximately 0.5 even heated for 100 hours. Heat treatment of coatings changed wear morphology from the "tear" and "fiiiTows" into minor injury, but it didn't change the wear morphology of 20 steel.
Keywords: supersonic arc thermal spray, FeCoCr coatings, thermal- shock resistance, the property of anti-oxidation at high temperature, the property of anti-curing at high temperature, wear resistance
本站文章未经允许不得转载；如欲转载请注明出处，北京桑尧科技开发有限公司网址：http://en.sunspraying.com/
|
