舶用原動機の耐熱鋼とその盛金用合金のアルミナイジング処理
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概要
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Hot corrosions of marine engine steels have often been experienced in operations with fuel oil C Fuel oil C has approximately 40〜400 ppm vanadium, 50 ppm Na and 3〜3.5 wt% sulphur. The controlling factors against its corrosive effect are oil ash deposits containing V_2O_5, Na_2SO_4 SO_3 at elevated temperature 500 to 700℃, pulsating combustion pressure, and so on. It is the aim of the present paper to describe an aluminized process as protective to hot corrosions of heat resistant steels on marine engine service. The results obtained from this study were as follows. (1) None of the alloys used in the typical marine engine and investigated in the present experiment has satisfactory resistance to vanadium attack corrosions, although austenitic alloys-14 Cr-14 Ni-2 W and territic alloy-2 Si-11 Cr-1 Mo, have been found as having comparatively high resistance. In general the resistance may be the function of the base composition, i. e., the Ni ; Cr ; Fe. (2) At service temperature, 600℃, the alloy's resistance to vanadium attack as well as to the scaling loss and such mechnical properties as fatigue life, shockwearing, etc., has been remarkably improved by the aluminized process. (3) However, it is less effective if micro cracks are initiated in the intermetallic compound formed on the surface of base material during the pulsating heats. It is likely that the intermetallic compound layer is stable against crack-initiations during the heating process if proper base materials, such as austenitic alloys 14 Cr-14Ni--2 W, are selected, whose thermal expansion is approximate to that of the surface layer.
- 1969-04-15