Al および Pt-Al コーティングした Ni 基超合金 IN-738LC の耐燃焼ガス腐食性

概要

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Pack cementation process has been applied for aluminide and platinum-aluminide coating on a nickel-base superalloy IN-738LC. Burner rig test using light oil containing 0.33%S was carried out for the evaluation of hot corrosion resistance. Aluminide coatings have two coating layers. The outer layer is high-Al NiAl and the inner layer consists mainly of low-Al NiAl. Hot corrosion resistance of the aluminide coatings can be improved by increasing the thickness of the outer layer. In the burner rig tests at 850℃ or below, the aluminide coatings whose outer layer thicknesses are about 80μ are more hot corrosion resistant than the platinum-aluminide coatings made by electroplating of platinum of 7μ thickness and aluminizing at 1120℃. This difference is attributed to the preferential attack of the PtAl_2 dispersed in the outer layer of the platinum-aluminide coatings. In the burner rig test at about 1000℃, the platinum-aluminide coatings are more hot corrosion resistant than the aluminide coatings, because of dissolution of the undesirable PtAl_2 particles into the matrix and the increased Pt concentration in the coating layer, both due to the rapid diffusion of atoms at the high temperature.
1983-06-01