Research On Burning Charcteristics Of Aircraft Engine Titanium Alloy

Titanium and titanium alloys with its superior performance has been widelyapplied to aircraft engine industry. But because of the characteristics of titanium alloyitself, resulting in titanium alloy were easy to catch fire and be burning in aero-engineapplication environment. Thereby, Application of the titanium alloy in advanced aeroengine is limited to some extent. In order to meet the requirements of advancedaero-engine and prevent the titanium-burning and reduce the weight of aircraft toincrease thrust-weight ratio, the people must study the subject of combustion of titaniumalloy. The combustion process is very complex and difficult to control, The paperstudied on the oxidation behavior of titanium alloys and its combustion products toreveal the relationship between high-temperature oxidation behavior and combustionbehavior and explore the mechanism of alloy combustion behavior.In this paper, the experimental process is divided into two parts, Experimentprocess of this paper is divided into two parts. One part analysed oxidation mechanismand established related model by studying the high temperature oxidation behavior ofTi40and Ti17alloy. The second part defined studied combustion zone and analyseddifferent regional characteristics. It explained the similarities and differences betweentwo types of titanium alloy in oxidation and combustion, and revealed the essence ofdifferent types of combustion behavior.The experimental results show that the melting point of V₂O₅could be boundary ofoxidation mechanism of Ti40alloy. The oxidation at temperature below700℃, the mainprocess of oxidation is outward growth of the V₂O₅in blending oxidation filmpreferentially. The oxidation mechanism is controlled by diffusion mechanism of Velements in the V₂O₅. Oxidation at temperature above700℃, fusion volatilization ofV₂O₅, causing oxidation layer porosity, oxide layer is mainly composed of TiO₂and SiO₂. There are enrichment layer of V, Cr elements in the interface of oxide layer andthe substrate. Under this condition, the oxidation of Ti40is controlled by diffusionmechanism of V element inβ-Ti. Oxidation of Ti17alloy at temperatures above700℃,oxidation behavior will increase and oxidation layer is porous. There is not a barrierlayer which can prevent diffusion of the O element inward at high temperature.Titanium alloy can be divided into4sections, combustion surface（CS）, moltenzone（MZ）, transitional zone（TZ） and influence zone（IZ）. The CS of two alloys is mainlyconsist of TiO₂, and with oxide of V. Cr₂O₃and SiO₂are detected on CS of Ti40. MZ ofTC4is in loose and porous state. There are lots of cracks and holes in the TZ and IZ;MZ of Ti40is compact, between MZ and IZ there is a TZ which is rich of V and Cr, itcan stop oxygen diffusing effectively. From the MZ to matrix, oxygen content reducesgradually, and oxide of Ti with different valence state is detected. Because of effect ofoxygen, the hardness of the two alloy increase after combustion, increment of Ti40ismuch greater than that of TC4. The special oxidation properties of Ti40alloy canexplain burn-resistant character of Ti40alloy in some way.