EFFECT OF Bi ADDITION ON THE CORROSION RESISTANCE OF Zr-4 IN SUPERHEATED STEAM AT 400 ℃/10.3 Mpa

Abstract Small amounts of a number of alloying materials were added to Type 304 stainless steel in an effort to improve its corrosion resistance to superheated steam at 650 C (1202 F), 42 kg/cm2. Aluminum and siliconwere valuable additions, but the amount of aluminum required to reduce the corrosion rate significantly embrittled the alloy. Type 304 containing about 3w/oSi appeared to be a practical alloy. In a similar fashion, the addition of about 3w/oAl to Incoloy 800 greatly improved its resistance to static superheated steam. Films stripped from samples corroded in steam with various prior surface preparations were examined by electron microscopy and chemical analysis in an attempt to clarify the reasons for differing corrosion behavior. It was concluded that the rapid diffusion of chromium into the corrosion films formed on mechanically worked surfaces is the key factor in the improved corrosion resistance of these surfaces.

Download Full-text

Assessing the corrosion resistance of chromium-aluminum steels in superheated steam

Soviet Materials Science ◽

10.1007/bf00716921 ◽

1976 ◽

Vol 11 (2) ◽

pp. 229-230

Author(s):

V. G. Makarenko ◽

I. A. Povyshev

Keyword(s):

Corrosion Resistance ◽

Superheated Steam

Download Full-text

Superheated Steam Of Zirconium Alloys Containing Small Amounts Of Iron and Copper or Nickel

CORROSION ◽

10.5006/0010-9312-21.4.113 ◽

1965 ◽

Vol 21 (4) ◽

pp. 113-124 ◽

Cited By ~ 5

Author(s):

S. GREENBERG ◽

C. A. YOUNGDAHL

Keyword(s):

Corrosion Resistance ◽

Corrosion Rate ◽

Corrosion Product ◽

Flow Rate ◽

Superheated Steam ◽

Zirconium Alloys ◽

Oxygen Absorption ◽

Exposure Temperature ◽

Hydrogen Mixtures

Abstract Alloys of zirconium containing small amounts of iron and copper or nickel have corrosion resistance in superheated steam superior to that of the Zircaloys. At 540 C (1004 F) and 600 psi lowest rates are about 4 mdd (2.4 mpy) and at 650 C (1202 F) and 600 psi rates are about 6.8 mdd (4.1 mpy). High initial rates lead to an extrapolated intercept of about 4 mg/sq cm at 650 C (1202 F). The thickening films are subject to cracking at sharp radii. Absorption of corrosion product hydrogen decreases markedly as exposure temperature is raised from 540 to 650 C (1004 to 1202 F). This phenomenon is not understood. Metal embrittlement due to oxygen absorption becomes an increasingly serious problem as temperature is raised. Corrosion rate at 650 C (1202 F) is not affected by flow rate (300 ft/sec) or by presence of oxygen or oxygen-hydrogen mixtures in the steam.

Download Full-text

Microstructures of Ti-1.5 w/o Ni Alloys with Mo and A1 Additions

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113895 ◽

1975 ◽

Vol 33 ◽

pp. 54-55

Author(s):

Anna C. Fraker

Keyword(s):

Corrosion Resistance ◽

Beneficial Effect ◽

Crevice Corrosion ◽

Local Corrosion ◽

Precipitate Size ◽

Ni Alloys

Small amounts of nickel are added to titanium to improve the crevice corrosion resistance but this results in an alloy which has sheet fabrication difficulties and is subject to the formation of large Ti2Ni precipitates. These large precipitates can serve as local corrosion sites; but in a smaller more widely dispersed form, they can have a beneficial effect on crevice corrosion resistance. The purpose of the present work is to show that the addition of a small amount of Mo to the Ti-1.5Ni alloy reduces the Ti2Ni precipitate size and produces a more elongated grained microstructure. It has recently been reported that small additions of Mo to Ti-0.8 to lw/o Ni alloys produce good crevice corrosion resistance and improved fabrication properties.

Download Full-text