The coke in the coils has a serious impact on the long-term and stable operation of the ethylene plant . Inhibiting coking of the cracking furnace is an important issue. In this paper, the Cr/CeO 2 coatings were prepared on the surface of 310S stainless steel by high-velocity oxygen-fuel (HVOF) spraying. The anti-coking performances of the bare 310S specimen and the Cr/CeO 2 coatings were tested by using the pyrolysis of naphtha . The results show that the coating with the thickness of 10–15 μm and a very small number of pores was built up by the obviously deformed splats and the coating/substrate interface is jagged bond. The white area on the surface of Cr/CeO 2 coatings mainly includes CeO 2 . However, the gray area is made of Cr or Cr 2 O 3 . Compared with the bare 310S specimen, the coking inhibition rates of coatings are 48.7%, 58.9%, 76.1% and 88.9% when the ratio of Cr and CeO 2 powder is 19:1, 9:1, 4:1 and 3:2, respectively. With increasing the relative ratio of CeO 2 , more white areas without coke are exposed. The CeO 2 surface can not only inhibit catalytic coking, but also promote the reaction of water vapor and coke.
Liu Ji,Chen Tongzhou,Duan Haitao,Yuan Chengqing,Bai Xiuqin
Cavitation erosion is a major failure mode of hydraulic turbine components. Coatings could be an effective solution to this problem. In this study, a CeO2-modified (1 wt%) dual-scale WC-10Co-4Cr powder (WC composed of 70 wt% micrometer WC (2.5 μm) and 30 wt% nanometer WC (100 ~ 200 nm)) was fabricated by agglomeration and sintering. CeO2-modified dual-scale WC-10Co-4Cr coatings (C-coating), dual-scale WC-10Co-4Cr coatings (D-coating), and micrometer WC-10Co-4Cr coatings (M-coating) were then deposited using a high-velocity oxygen fuel (HVOF). The mechanical properties and cavitation erosion behavior of these coatings were studied. The results showed that the CeO2-modified WC-10Co-4Cr coatings could effectively reduce decarburization in the powder preparation and HVOF process, the coatings having the highest WC retention rate. The C-coatings possessed a higher fracture strength (6.3 MPa m 1/2 ) and hardness (1348.2 HV0.3) than the D-coatings by more than 8.6 and 3.0%, respectively. The cavitation erosion resistance of the WC-10Co-4Cr coatings was affected by their microstructure and mechanical properties. The CeO2-modified coatings exhibited improved fracture toughness and hardness, reduced porosity, and, as a result, the C-coatings had the best cavitation erosion resistance.
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