Relationship between the effect and the amount of SiO2 addition on the photo-generated hydrophilicity of TiO2 films isinvestigated. X-ray diffraction, UV-Vis spectrumand Fourier transform infrared spectroscopy are used to determine film behaviorand the hydrophilicity is assessed by contact angle measurement. It is found that addition of 40 mol% SiO2 to TiO2 is mosteffective for reducing the contact angle of water. The contact angle of water can maintain low for a long time in dark place.SiO2 addition has a suppressive effect on the crystal growth of TiO2 in calcination and enhances the transmittance of thecomposite films. SiO2 and TiO2 form single oxide particles in the films, but a part of complex oxide may be formed. Ti-O-Sibonds increase the acidity which induces the increasing of the hydroxyl content in the composite films.

Hot corrosion often takes place at elevated temperatures in gas turbines and other equipment. However, hot corrosionin ethylene cracking tubes is seldom seen. In this case, an examination of pitting in ethylene cracking tubes made ofHP 40 steel (25Cr–35Ni) which failed in weldments (Ni-base alloy) has been conducted to identify the cause of failure.Results show that these failures had been caused by hot corrosion produced by Na2SO4. A molten state was noticedfrom the morphology. Analysis revealed that pitting in tube weldment was caused by high-temperature hot corrosion(Type I corrosion and Type II corrosion) produced by Na2SO4. The mechanism of different types of hot corrosion isdiscussed. Finally, the cause of hot corrosion is discussed including the origin of Na,V, S and the formation of Na2SO4.The influence of temperature, composition and microstructure of materials on hot corrosion is discussed. To avoid suchhot corrosion, precautions should be taken, including increasing Cr content in weldments, decreasing protrusion inweldments, washing internal surfaces of tubes with hot steam regularly.

Eleetroless NiP coating has stochastic nonlinear structure, which was in far from equi-librium and instability state. Fractal theory, an effective method for solvin9 nonlin-ear system, was introduced to describe the coating structure quantitatively. Disorderand self-similarity characteristics, which a~ the two basic features of fractal, were plained in this paper for the first time. The results show that amorphous NiP structuexhibits scale invariance and can be quantitatively characterized by ]rectal dimension.Based on the fractal principte a two-dimensional computer simulation on electrolessNiP deposition was carried out and it is in agreement with the experimental Tsult. Fi-nally, the fractal dynamics and process of atom growth were investigated. The resultsshow that the atom deposition is reaction limited growth process.

Effects of CeO2 or/and La2O3 addition on photo-generated hydrophilicity of TiO2/SiO2 film were investigated in this paper with the testingof X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible spectroscopy (UV-vis) and scanning electronmicroscopy (SEM). It is found that appropriate amount of CeO2 or/and La2O3 is effective on the super-hydrophilic property of TiO2 becauseof the increase of oxygen vacancies. The super-hydrophilic property of the composite film becomes better during UV irradiation and it canmaintain for a long time in the dark with the synergetic effect of rare earth oxides and SiO2.

The failure of ethylene cracking tubes at an elevation of about 5 m in radiant chambers after one-year service hasbeen analysed. Bulges and circumferential cracks, oriented towards the walls/burners, are the result. The investigationincluded tensile tests, optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS),and X-ray diffraction (XRD) analysis. Analysis revealed that ruptures found in the tubes were caused by overheating ofthe tubes because of inappropriate burning of bottom burners. Significant growth of precipitates of carbide wasobserved in the failed zones which results in the drastic reduction of material ductility. The bulged zones also showeda globular form of grains. Tube bowing, due to the restricted growth during the hot expansion, promotes cracks. Toavoid such overheating, precautions should be taken while improving the burning condition of the bottom burnersand decreasing the peak tube metal temperature. It is necessary to check the tube temperature periodically in criticalpositions and one should ensure that the temperature is less than the design temperature.

The present work studies the AISI304 weld cracking mechanism of AISI321 austenite stainless steel of flue gas pipe,which served up to 60,000 h at 650-700℃. The performance and microstructure of failed material were characterizedby impact test, optical microscopy, scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy(EDS), X-ray diffraction (XRD). The results show that cracks ware caused by embrittlement of weld metal and thermalstress. Needle like r-phase precipitation during service is primarily responsible for significant degradation in mechanicalproperties and microstructures of weld metal. Needle type r-phase is a severe stress-raiser and plays a role as crackinitiator at the interface with matrix. In addition, maximum equivalent stress is about 175 MPa in the elbow whichis near to the yield stress of the steel. It is highly possible that a crack will be initiated under above stress conditionand will propagate faster along embrittled r-phase. Several approaches should be employed to control r-phase precipitationin weld. These approaches include: decreasing content of ferrite and M23C6 carbide in weld and selecting Nbadded weld wire during welding.

The failure of a bellow expansion joint of 304 stainless steel has been analysed. Stress corrosion cracking (SCC)caused by wet hydrogen sulfide was responsible for the failure. Observation of metallographic sections indicated thatthe crack is transgranular SCC (TGSCC) with cracking in a direction perpendicular to axial stress. Scanning electronmicroscopy (SEM) analysis of the fracture surface showed that the cracks are cleavage and quasi-cleavage with obviousfan-shaped marking and branched propagation, which indicated that the cracking mode is hydrogen-induced cracking(HIC). Metallographic and SEM analysis showed strain-induced martensite transformed from austenite during the coldworking process. This resulted in a considerable susceptibility to sulfide stress corrosion cracking (SSCC). The quantitativeanalysis results of XRD indicated that the content of martensite was up to 44%. The location of HIC at theexpansion joint located at crests with maximum cold work deformation and hardness.

Ethylene cracking tubes of HP40 grade (25Cr–35Ni–0.4C) creep-resistant austenitic steel which failed after 80,000 h servicewere investigated for quantitative cavity evaluation. The results show that the creep cavity area fractions (Ω) present littledifference from outer surface to inner surface through the thickness, and larger difference on different tube outer surfaces. TheΩ obtained from the outer surface can stand for creep damage state for ethylene cracking tubes. The relationship between creepcavity area fraction and continuum damage mechanics is discussed. At failure, the critical value of damage variable D=1 iscorresponding to Ω= 2.8% measured on the tube outer surface.