Y Gong, Z-G. Yang/Materials and Design 32 (2011)671-681 679 c (d)4o 500 000100200 000100200300400 Fig. 16. Morphologies and EDS of the cross-section of the perforated manhole door(a )macroscopic morphology, (b)SEM micrograph, (c)EDS of site A and(d) EDS of site B Table 5 Site a 14.25 9030.13 2.53 1.60 25.31 1297 1840.665342 XRF results of the brown rust(wt%). Element Al Wt% 0.3141.220.744 25302082527.0Rest Fig. 17. XRD results of the brown rust. fuels. Commonly, sulfur is activated at high temperatures and is al- ways in forms of hydrogen sulfide(H2S), mercaptan(RCH2CH2SH) corrosion actually occurred at the same time under which condi- and simple sulfur (S), which are all easy to react with the metal ele- tion, the defects grew increasingly larger and deeper, and eventu- ments in the materials to form metal sulfides, such as FeS, Nis, Mns ally resulted in the perforation and so on. Compared with the most familiar corrosion products After determining the causes of the perforation on the nozzle, the metal oxides, the metal sulfides usually perform four distinct now it was wondered what the actual factors were leading to the features [30. 1. e. the large amount of lattice defects for diffusion, fracture on its inlet tube for primary air. As was detected above the poor thermodynamic stability, the large internal stresses to that the fractured tube had suffered severe thinning of its wall crack, and the ease to form low melting point eutectics like Fe- thickness, seen in Fig. 2c, hence it can be inferred that the fracture FeS, Ni-NiS, FeO-FeS, etc. Consequently, the metal sulfides would was relevant to erosive wear on the pipe. Commonly speaking. easily decompose and therefore enlarge the defects. In addition, three reasons can usually be ascribed to the erosive effect on noz- it was obvious that the ablation and the high-temperature sulfur zles in a CFB boiler, (a)the impact on outside walls of nozzles fromfuels. Commonly, sulfur is activated at high temperatures and is al￾ways in forms of hydrogen sulfide (H2S), mercaptan (RCH2CH2SH) and simple sulfur (S), which are all easy to react with the metal ele￾ments in the materials to form metal sulfides, such as FeS, NiS, MnS and so on. Compared with the most familiar corrosion products – the metal oxides, the metal sulfides usually perform four distinct features [30], i.e. the large amount of lattice defects for diffusion, the poor thermodynamic stability, the large internal stresses to crack, and the ease to form low melting point eutectics like Fe– FeS, Ni–NiS, FeO–FeS, etc. Consequently, the metal sulfides would easily decompose and therefore enlarge the defects. In addition, it was obvious that the ablation and the high-temperature sulfur corrosion actually occurred at the same time, under which condi￾tion, the defects grew increasingly larger and deeper, and eventu￾ally resulted in the perforation. After determining the causes of the perforation on the nozzle, now it was wondered what the actual factors were leading to the fracture on its inlet tube for primary air. As was detected above that the fractured tube had suffered severe thinning of its wall thickness, seen in Fig. 2c, hence it can be inferred that the fracture was relevant to erosive wear on the pipe. Commonly speaking, three reasons can usually be ascribed to the erosive effect on noz￾zles in a CFB boiler, (a) the impact on outside walls of nozzles from Table 5 Chemical compositions on cross-section of the perforated manhole door (wt.%). Element C O Si Al Cu S Site A / 14.25 4.90 30.13 2.53 1.60 Site B 25.31 12.97 5.81 1.84 0.66 53.42 Table 6 XRF results of the brown rust (wt.%). Element Al Si S K Ca Mn Fe O Wt.% 0.314 1.22 0.744 0.225 3.02 0.825 27.0 Rest Fig. 17. XRD results of the brown rust. Fig. 16. Morphologies and EDS of the cross-section of the perforated manhole door (a) macroscopic morphology, (b) SEM micrograph, (c) EDS of site A and (d) EDS of site B. Y. Gong, Z.-G. Yang / Materials and Design 32 (2011) 671–681 679