Short Time Oxidation Behavior Of Two Directional Solidification Superalloys At Different Temperatures

Ni-base single crystal superalloy is key material for the manufacturing of turbine bladewhich is the important parts of advanced aero-engines. In real service conditions, the blade willbear higher temperature, so that, the materials of blade must call for good oxidation resistance.At present, the studies of oxide of blade materials focus on long time oxide and cycling oxide,but for the aeroengine, the short time oxide of blade is very important, so the oxidation ofdirectional solid MC2Ni base superalloy and DZ40M Co base superalloy were investigated inthis paper.The study of oxidation dynamics curves of Ni base superalloy at short time indicated thatthe temperature is one of a importance effect factors for the oxide gain of the alloy, as a result ofthe investigation, the oxide order is that800℃,700℃and600℃. The oxide dynamics accordwith some rules when the alloy was heated at900℃to1100℃, the oxide velocity expeditedwith the increasing of temperature. During the oxidation, the oxide behavior was controlled bysurface reaction at the nonage, and the diffusion reaction dominated at the evening of oxidation.The investigation of oxidation mechanism of the Ni base superalloy at different temperatureindicated that the oxides were the mixture of Al₂O₃,NiO,Cr₂O₃and TiO₂, and some NiO wereremained in local area of the surface. The integrate oxidation film formed when the alloy washeated at1000℃, and when heated at1100℃, some spinel NiCr₂O₄formed at the outer layer,and the local area was very loosen, at the same time, some desquamated oxidation films wereobserved.The investigation of oxidation mechanism of the Co base superalloy at differenttemperature indicated that some CoO formed at the surface of the alloy when heated at900℃,afterward some mixture of Cr₂O₃and Al₂O₃were observed. With the increasing of the heatedtime, the amount of Cr₂O₃and Al₂O₃increased. When the alloy was heated at1000℃and1100℃, the number of Cr₂O₃and Al₂O₃reduced gradually, and some spinel CoCr₂O₄wereobserved.