ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
The machinery used in coal thermoelectrical plants usually is submitted to erosive wear.The erosive wear occurs mainly in the metallic pipe set of heat exchangers due the flow of hot gasescarrying erosive particles. Jorge Lacerda’s thermoelectrical complex at Capivari de Baixo city holdsseven power units, where two units use approximately 20 000 ASTM A178 heat pipes. The set issubmitted to a semester maintenance schedule (preventive and corrective) where the damaged pipesare changed. So, in this work a set of erosive wear accelerated tests according ASTM G76 wereperformed in order to develop and specify materials and methods to diminish the erosive actioncaused by the combustion gases over the heat pipes. Specimens were coated with WC12Co andCr3C2-25NiCr alloys using the HVOF technique and the coated specimens were tested at 450°C, theheat pipes working temperature. Silica was used as abrasive material at 30° and 45° impact angles,simulating a harder erosive condition than the real condition. The best performance coating atlaboratory scale was later used in field condition. The results showed the coated specimenperformance is better than the ASTM A178 alloy. The erosion resistance of the Cr3C2-25NiCr andWC12Co coatings is eight times higher than the uncoated alloy, and the coatings also presented abetter corrosion resistance. This feature is important, because despite the erosive action thecirculating gases also present a large amount of sulfur in their composition. Sulfur at lowertemperatures forms H2SO4, causing intense corrosion of the pipes located at the heat exchangerscolder parts. Based on the results and considering the coating costs the Cr3C2-25NiCr alloy wasselected to coat a set of pipes mounted at the region of the heat exchanger with the most intenseerosive wear. At the moment these coated tubes are in field operation and under observationregarding their performance in comparison with the uncoated pipes located at the same heatexchanger. The real operation conditions of the coated pipes will be estimated from the field lifecycle analysis, and after all the cost-benefit of the studied coating
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.591-593.49.pdf
Permalink
