Influence of RE oxide additions on hot corrosion bdhaviors of NiAl coatings

INFLUENCE OF RE OXIDE ADDITIONS ONHOT CORROSION BEHAVIORS OF NiAl COATINGS￣①

ＩＮＦＬＵＥＮＣＥＯＦＲＥＯＸＩＤＥＡＤＤＩＴＩＯＮＳＯＮＨＯＴＣＯＲＲＯＳＩＯＮＢＥＨＡＶＩＯＲＳＯＦＮｉＡｌＣＯＡＴＩＮＧＳ￣①Ｍａ，Ｘｉｎｇｑｉｎｇ；Ｌｉ，Ｔｉｅｆａｎ（ＣｏｒｒｏｓｉｏｎＳｃｉｅｎｃｅＬａｂｏｒａｔｏｒｙ，ＡｃａｄｅｍｉａＳｉ...

The influence of rare-earth(RE) oxide additions, e. g. Y_2O_3 and Gd_2O_3 on the hot corrosionbehaviors of the NiAl coatings exposed to the Na_2SO_4+25wt.- % K_2SO_4 fused salt at 850℃ wasstudied. The experimental results show that the RE oxide additions can not only reduce the corro-sion rates of the coatings, but also lighten the corrosion degree of the sulfides on the coatingsthrough the formation of stable RE-oxygen-sulfides which are aggregated in the surface corrosionareas of the coatings. With increasing additions , the effect of the RE oxides against hot corrosionwill improve. Furthermore, the corrosion form of the sulfides will change from imhomogeous cor-rosion , in which case the intracrystalline local corrosion is predominant , to mixed type corrosion ,in which case the transgranular corrosion is predominant.