Weld overlaid

LL. Attack in nozzle attachment area of a vessel weld overlaid with Type 309Nb. 

Reactors are normally made of low-alloy steel (selected per API Publication 941) and clad or weld overlaid with type 347 (UNS S34700) SS. The stabilized grades (i.e., type 947 or 321 [UNS S32100] SS) are normally used for all stainless equipment in these units to avoid intergranular stress corrosion cracking (SCC) during downtime. Downtime corrosion is discussed in the next section of this chapter, Feed-Effluent Exchangers."... 

Two sections of steel condenser tubing experienced considerable metal loss from internal surfaces. An old section contained a perforation the newer section had not failed. A stratified oxide and deposit layer overlaid all internal surfaces (Fig. 5.14). Corrosion was severe along a longitudinal weld seam in the older section (Fig. 5.15). Differential oxygen concentration cells operated beneath the heavy accumulation of corrosion products and deposits. The older tube perforated along a weld seam. 

If austenitic stainless steel parts exposed to conditions that promote intergranular corrosion are to be fabricated, hard faced, overlaid, or repaired by welding, these parts shall be made of low-carbon or stabilized grades. 

Waste-to-energy boilers Coal-fired Boilers Pulp and paper digesters Kraft recovery boilers Municipal waste containing chloride, sulfur, alkali metals, zinc and lead Sulfidation attack boiler tube wastage (50-60 mpy) Thiosulfate and polysulfides Sulfate, thiosulfate Chloride 59 (alloy 625 overlay weld metal used) 8 (alloy 625 and 309 SS) 21 (overlaid with 309 SS) 11 (309 L on lower furnace sidewalls 625 on floor tubes and smelt opening)... 

Coatings for carbon and Cr-Mo steels are often overlaid, and of composition corresponding to the austenitic alloys listed in Table 5-1, although several steel products are diffusion aluminized, particularly for resistance to sulBdation attack (Sivakumar and Rao, 1982 Bayer, 1995). The weld overlay process, in which an arc-welding method is used to deposit a 2-3 mm coating (i.e., clad-... 

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