CaSO_4 と C との共存下における軟鋼, 16Cr 鋼, Ni および Ni-20Cr 合金の高温腐食

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Ash deposits, especially alkali and alkaline earth sulfates, have been said to be an important source of the hot corrosion of valves and pre-combustion chambers in automobile diesel engines. In the present work, to clarify the corrosion behavior, crusible-type corrosion tests by CaSO_4-C mixtures have been carried out on pure nickel, iron and their Cr-containing alloys in the temperature range from 650°to 1100℃ for 4h in air. The results obtained from gravimetric measurements and metallographic examination are summarized as follows : 1) The CaSO_4 alone is not corrosive for above metals and alloys, however the addition of C causes very severe attack, especially on Ni-20% Cr alloy. 2) On Ni and Ni-20% Cr alloy the temperature dependence of the corrosion caused by CaSO_4-20% C mixture is different from that of well-known SO_2 gas corrosion ; nickel shows a monotonic increase in weight loss with temperature and Ni-20% Cr alloy shows a maximum at about 875℃. 3) In the corrosion scale, the sulfides and the oxides of each element in alloys are recognized ; this scale morphology is characteristic of the sulfidation-accelerated oxidation.
社団法人日本鉄鋼協会の論文
1983-10-01