Stainless steels nickel, effect

Molybdenum alloying is not particularly beneficial for SCC resistance of austenitic stainless steels nickel is the most important beneficial element. Referring to Figure 26, Mo increases and by about the sme amount, through its effect on the localized corrosion velocity, while Ni (above 10%) decreases the crack velocity, thus lowering E [68,111,112]. 

Storage. For receiving glycerol from standard 30.3-m (8000-gal) tank cars (36.3-t), a storage tank of 38—45-m ((10-12) x 10 — gal) capacity should be employed. Preferably it should be of stainless steel (304 or 316), of stainless- or nickel-clad steel, or of aluminum. Certain resin linings such as Lithcote have also been used. Glycerol does not seriously corrode steel tanks at room temperature but gradually absorbed moisture may have an effect. Therefore, tanks should be sealed with an air-breather trap. 

Nickel and Nickel Alloys A wide range of ferrous and nonfer-rous nickel and nickel-bearing alloys are available. They are usually selected because of their improved resistance to chemical attack or their superior resistance to the effects of high temperature. In general terms their cost and corrosion resistance are somewhat a func tion of their nickel content. The 300 Series stainless steels are the most generally used. Some other frequently used alloys are hsted in Table 10-35 together with their nominal compositions. For metallurgical and corrosion resistance data, see Sec. 28. 

D02 G.E. Duvall, D.E. Davenport, and J.J. Kelly, Metallurgical Effects of Explosion-Induced Shock Waves, in Research Seminar on High Nickel Alloys for High Temperatures, Iron-Nickel Alloys, Stainless Steels (The International Nickel Co., New York, 1960). 

Total world production of nickel is in the region of 1.0 million tonnes pa of which (1995) 25% comes from the former Soviet Union, 18% from Canada, 12% from New Caledonia and 10% from Australia. The bulk of this is used in the production of alloys both ferrous and non-ferrous. In 1889 J. Riley of Glasgow published a report on the effect of adding nickel to steel. This was noticed by the US Navy who initiated the use of nickel steels in armour plating. Stainless steels contain up to 8% Ni and the use of Alnico steel for permanent magnets has already been mentioned (p. 1114). 

Steels and stainless steels show preferential nucleation of pits at inclusions, most notably sulphide inclusions ". Other sulphur-rich regions in ferrous and nickel-based alloys may also lead to premature failure. It has been shown that accumulation of sulphur on the surface of these materials retards passivity and enhances dissolution of the metal. These effects occur in any solution in which the metal shows an active region and they are also preferential pitting sites in the presence of chloride. A recent notion for... 

Pakhomova, N. A. and Levin, I. A., Effect of Grain Size on the Inter-crystalline Corrosion of Stainless Steel Type 18-8 , Zashch. Metal, 9, 676 (1973) C.A., 80, 86207j Brown, M. H. and Kirchner, R. W., Corrosion of High Alloy Weldments 1. Sensitisation of Wrought High Nickel Alloys , Corrosion, 29, 470 (1973)... 

Tomashov, N. D., Chernova, G. P. and Markova, O. N., Effect of Alloying Elements on the Tendency of Stainless Chromium-Nickel Steels to Pitting Corrosion , Sa. Korroziya Meta i Splavov, 73 (1963) C.A., 60, 3805b... 

Selective removal of the less noble constituent has been demonstrated by chemical analysis in the case of nickel-rich alloys in fused caustic soda or fused fluorides ", and by etching effects and X-ray microanalysis for Fe-18Cr-8Ni steels in fused alkali chlorides. This type of excessive damage can occur with quite small total amounts of corrosion, and in this sense its effect on the mechanical properties of the alloy is comparable with the notorious effect of intercrystalline disintegration in the stainless steels. 

Contact of brass, bronze, copper or the more resistant stainless steels with the 13% Cr steels in sea-water can lead to accelerated corrosion of the latter. Galvanic contact effects on metals coupled to the austenitic types are only slight with brass, bronze and copper, but with cadmium, zinc, aluminium and magnesium alloys, insulation or protective measures are necessary to avoid serious attack on the non-ferrous material. Mild steel and the 13% chromium types are also liable to accelerated attack from contact with the chromium-nickel grades. The austenitic materials do not themselves suffer anodic attack in sea-water from contact with any of the usual materials of construction. 

Fig. 8.30 Effect of nickel content on the susceptibility to stress-corrosion cracking of stainless steel wires containing 18-20% chromium in a magnesium chloride solution boiling at 154°C...

Fig. 8.49 Effect of nickel content on residual ductility of austenitic stainless steels (after...

Compared with ferritic carbon and low-alloy steels, relatively little information is available in the literature concerning stainless steels or nickel-base alloys. From the preceding section concerning low-alloy steels in high temperature aqueous environments, where environmental effects depend critically on water chemistry and dissolution and repassivation kinetics when protective oxide films are ruptured, it can be anticipated that this factor would be of even more importance for more highly alloyed corrosion-resistant materials. 

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