The buckling spallation behavior of the cyclic oxidation scales for high temperature alloys has been described as a strut rest ing on elastic foundation under critical stability.According to the buckling pro pagation analysis using finite elements method,the model of cyclic oxidation ki netic has been developed.The calculation results for Fe-Ni-Cr-Al alloys are cons istent with the experimental results,indicating the validity and suitability of the model.

The oxidation behavior of a Ti45Al10Nb allo y has been studied in oxygen and air atmosphere at 800～960℃.It was shown that th e alloy is better than Ti-50Al alloy in oxidation resistance.The oxidation rate in weight gain of Ti45Al10Nb is comparable to or even better than that of ox id ation resistant steel.It was also found that the rate of oxidation in air decrea ses obviously than that in pure oxygen.Based on the result of X-ray or EDS analy sis,the oxide scales consist of TiO2 and Al2O3,but TiN was identified in the scale tested in air.It was concluded that TiN in the scale,which was stabili zed by Nb,was responsible for the decreased rate of oxidation in air.

A Fe20Cr45Al microcrystalline coating an d a Fe20Cr45Al-Y2O3 oxide dispersed microcystalline coating have been prep ared on the Fe20Cr45Al alloy by high frequency electro-spark deposition techni que with home-made equipement.Isothermal oxidation tests of the coated and uncoa ted specimens at 1000℃ and 1100℃ in air were carried out for 200h.The results show that the microcrystalline coatings with Y2O3 dispersed oxide particles el iminated the wrinkles emerged on the Al2O3 oxide scale completely,reduced th e oxide grain size,improved the spalling resistance and enhanced the compactness and the adhesion of oxide scales significantly.In the case of specimens with th e single microcrystalline coating,the wrinkles on oxide scales were only eliminat ed partly and oxide scales were composed of mixtures of wrinkled oxides and micr ocrystallized oxides.The effect of the coatings on oxidation kinetics relied on temperature,or the growing rate of oxide scales.At 1000℃ the weight-gain of all coated specimens reduced;while at 1100℃ the effects of both coatings on oxidat ion kinetics were trivial.It was proved that the microcrystalline structure and the dispersed Y2O3 oxide particles in the coatings have synergetic effects o n improving the protection of Al2O3 oxide scales.

The oxidation behaviors of Ag-In alloys with di fferent indium content were studied at different oxygen partial pressure control l ed by an oxygen pump system.It is shown that both In2O3 particles and nano-s ize fibres can form on the surface of Ag-In alloys at different conditions:P O2=021×10-5 Pa and 550℃,at which internal oxidation may occur in the Ag-In alloys.When Ag-In alloy oxidized at PO20.21×105 Pa,I n2O3 particles and pure Ag nodules appeared on the surface of Ag-In alloys.W hile at low oxygen partial pressures,nano-size In2O3 fibres formed on the su rface of Ag-In alloys.Increasing the Indium content in the alloys or decreasing system oxygen partial pressure can promote the formation of In2O3 on the sur face of alloys.

High temperature oxidation and hot corrosion be haviors of MCrAlY coating，thermal barrier coatings (TBCs) and gradient thermal barrier coatings prepared by electron beam physical vapor deposition (EB-PVD) ha ve been investigated.Although these coatings showed excellent oxidation behavior ，the mass gain for MCrAlY coatings was larger after being sprayed with a 2 mg/c m2 deposit of Na2SO4 and tested at 950℃.The lower mass gain for TBCs and GTBCs indicated that the ceramic coating has a benefit to improve the hot corros ion behavior.However，thermal cyclic life time for TBCs and GTBCs decreased duri ng hot corrosion testing.

The high temperature oxidation behavior of low pressure plasma sprayed(LPPS) NiCrAlY coating on nickel-base superalloy was stud ied at 1050℃ in a flow of O2,mixtures of O2 and 5%H2O under atmospheric p ressure.Oxide formed on the surface of LPPS NiCrAlY coating after oxidation at 1 050℃ in pure O2 consisted of Al2O3,whereas oxide formed on the surface of LPPS NiCrAlY coating after oxidation at 1050℃ in a mixture of O2 and 5%H2O is composed of Al2O3,Cr2O3 and NiO.The effect of water vapor on the cha racteristics of the oxide scale formed is attributed to the increase in Ni catio n transport.

High temperature corrosion behavior of A3 ste el was studied in V2O5+Na2SO4 at 700℃.The results indicated that severe corrosion of A3 steel occurred in V2O5+Na2SO4 at 700℃～850℃ and max imal corrosion rate was found in 85 mass% V2O5+15 mass%Na2SO4.The corros ion mechanisms were discussed.

Influence of heat treatment times at temperatur e of 1100℃ on the characteristics of NiCrAlY-ZrO2 interface and distributio n of elements was studied in thermal barrier coatings(TBCs) consisting of bond coat deposited by low pressure plasma spray (LPPS) and top coat deposited by ai r plasma spray (APS ) in this paper.

Photocatalytic titanium dioxide film in nano crytalline has been prepared by electrochemical oxidation process.It shows that amorphous titanium dioxide films are formed during the electrochemical oxidation process in the studied solution and applied voltage.Then heat treatment is carri ed out on the formed amorphous film to form nano crystallized titanium dioxide f ilm under the controlled temperature and heating time.The oxidation kinetics has been studied by measuring the film thickness and current density with oxidation time respectively.It shows that the film grows to an equilibrium thickness unde r certain oxidation voltage and the equilibrium thickness increases with the app lied voltage.The oxidation current density decreases with time in logarithm law under the applied voltage range from 0 to 80 V.The film crystalline size ranges from 10～30 nm and the film phase structure can be pure anatase as demonstrated by TEM and X-ray diffraction after the crystallization treatment.The photo abso r ption measurement demonstrated that the prepared film shows very strong absorpti on to the incoming light of near ultraviolet wave range.

T91 steels with and without the treatments,shot bla sted (shot),electrophoresis deposited RE coating (RE),and combined treatments of shot blasted and deposited RE coating (shot+RE),were oxidized at 600℃ in water vapor for 300 hours by tubing device containing high temperature deoxidizing wa ter vapor.The results show that the combined treatments can decrease the parabol ic rate constant,effectively improve the property of water vapor oxidation resis tance and be superior to deposited RE coating only.Through combined treatments,t he grain size of the oxide scale deceases from 3～5 μm to 0.5 μm.The effects o f shot blasted and electrophoresis deposition RE coating on the oxidation mechan ism are analyzed,and the effects of the combined treatments on diffusion mechani sm in the oxidation process and the oxide scale phase forms are also discussed.

A NiCrAlY bond coat had been deposited on a Ni- base single crystal superalloy by magnetron sputtering,and then a top coat (7 ma ss%Y2O3-ZrO2) had been deposited by electron beam-physical vapor depositio n (EB-PVD).The phase transformation of ceramic top coat was investigated and the surface morphology change of the samples was observed.It was found that the ZrO 2-7 mass% Y2O3 ceramic top coat deposited by EB-PVD showed columnar grain s which formed dense clusters and the surface was relatively dense.However there were gaps or holes among grain clusters,which allowed the lateral expansion and contraction of the ceramic columnar grains and allowed free expansion of the su bstrate over a relatively large range.After exposure to elevated temperatures,th e gaps among columnar grain clusters became larger.The relatively large gaps int erconnected into one another and formed microcracks.With thermal cycling going o n,the microcracks extended across and through the top coat.Also the Y2O3 con tent in nonequilibrium tetragonal phase decreased gradually,and the nonequilibri um tetragonal phase decomposed to equilibrium tetragonal and cubic phases.After 300 thermal cycles at 1050℃,small amount of monoclinic phase was formed from th e decomposition of the tetragonal phases.

The thermal barrier coatings (TBC),which Ni30C r12Al0.3Y bond coating was deposited by magnetron sputtering and ZrO2 ceramic top coating was deposited by electron beam-physical vapor deposition (EB-PVD),wa s produced on Ni-base superalloy.The bond coatings,which the mean grain size was less than 100 nm,were nanostructured coatings,and had good oxidation-resist ance.The ceramic topcoats,which were columnar structure,permitted larger strain in the coatings.The as-deposited ceramic coatings consisted of large quantity no nequilibrium tetragonal (t′),a small amount cubic (c) and monoclinic ( m) phases.The t′ phases,which had important role to the stabilization o f zirconia at high temperature,can not directly transform into m phase during co oli ng.During cyclic oxidation at 1050℃,the scale of the cast alloy had spalled aft er two cycles.After 100 cycles,the surface scale of single-crystal superalloy wa s mainly composed of NiO、Cr2O3,a little Al2O3 and pores by the Kirkenda ll effect.However,the ceramic coatings,which had microcrack,have not spalled and the thermally grown oxide (TGO) was Al2O3.There were some microcrack betwee n TGO and bond coating after 300 cycles.

The cyclic oxidation behavior of K40S,a kind of cobalt-base superalloy,with maximun temperatures at 950℃,1000℃ was studied .The alloy possesses excellent resistance when tested at 950℃ for 400 hours.At 1000℃,K40S exhibited weight loss behavior due to oxide scale spallation after 5 0 cycles of test.Primary oxide products at the early stage of oxidation are Cr 2O3,CoCr2O4 with a little amount of CoO.Nearly all of the formed Cr2 O3 were detached off after 400 thermal cycles.Other oxides such as Cr2WO6, NiCr2O4,volatile WO3 also began to develop due to depletion of chromiu m in the alloy surfaces.Silicon,manganese addition make K40S alloy more resis tant to cyclic oxidation than directionally solidified DZ40M alloy,which has sim ilar composition to K40S but contains no silicon,manganese elements in the a lloy.

The sulphation and oxidation corrosion resista nce of Ni3Al-based intermetallics has been investigated in this paper.In burning environment of inferior quality coal,Ni3Al-based alloy provided excellent prot ection against sulphation corrosion.Its properties of sulphation resistance is o ver 3.6 times that of 2520 heat resistant alloy,this is excellent commercial mat erial of sulphation corrosion resistance at high temperature. 

In this paper,the effect of diffusion treatment on hot dip aluminum coatings microstructure have been analyzed by means of EPM and XRD,the specimens diffused at 850 ℃ have two zones,but diffusion coating pr oduced at 950℃ have three zones.The cyclic thermal shock properties and weight gains of oxidation on diffusion layers have been investigated in air for 500 hou rs.The results show that the oxidation kinetic curves obey conventional paraboli c law,the optimum technical parameters is diffusion for 4 hours at 950℃ on dip 10min specimen.

The corrosion behaviors of Zr-Sn-Nb alloy (N18, N36) developed in China have been studied by out-of-pile autoclave in 360℃ wate r with 70 μg/g Li,in 400℃ and 500℃ high pressure steam.The results show that the nodular corrosion for two kinds of alloys did not occur after 500h,and Zr-4 alloy did after 4h in high-pressure oxygen at 500℃;that the weight gain of N18 samples is lower than Zr-4,and of N36 is higher than Zr-4 after 245 days in 400 ℃ high pressure steam;that the weight gain for two kinds of alloys samples is o nly 16%-25% that of Zr-4 after 300 days in 360℃ water with 70 μg/g Li.N18 allo y possesse s good corrosion resistance in both high temperature water and high pressure ste am.Addition of alloying element Nb in Zr-Sn binary system,on the one hand,solid solution of Nb in α-Zr can resist the detrimental effect of C,N impurities on c orrosion behavior,on the another hand,the formation of α-Nb second phase partic les and their uniform distribution in alloy can reduce greatly the oxidation rat io in high temperature water and high pressure steam.The nonuniform growth of o xide film occurs at the oxide film/metal interface,and that of oxide film become s more distinct after oxidant transition.