燃焼ガス雰囲気中における Ni 基耐熱合金単結晶の高温腐食に対する W/Ta 比の効果

概要

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Burner rig tests of nickel-base superalloy single crystals with various W/Ta ratio (W+Ta=7at%) were carried out at 900℃ for 7h in combustion gas flowing at Mach 0.5, prepared from 5ppm NaCl-containing air and 0.5% sulfur-containing fuel. The hot corrosion tests revealed that the alloys with higher W/Ta ratio were severely attacked. The cross sections of these alloys with high W/Ta ratio were characterized by a thin oxide layer, while that of the alloy with the lowest W/Ta ratio was characterized by a continuous aluminum oxide layer covered by a thick NiO layer. The hot corrosion behavior seems to depend primarily on W content rather than on Ta content ; the difference in hot corrosion behavior was explained by acidic fluxing of NiO and Al_2O_3 due to dissolution of tungsten oxide.
1990-09-01