Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Page 230 of 707

Fig. 4. Variation in elongation, tensile strength, and hardness with temperature. Watts bath pH 3 and 495 A/m2 (46 A/ft2 ). Shot peening the steel prior to plating helps minimize reduction in fatigue life upon cyclical stress loading. Highly stressed, high-strength steels are susceptible to hydrogen embrittlement during normal plating operations. Because nickel plating is highly efficient, hydrogen damage is unlikely to occur as a result of nickel plating per se. The pre- treatment of steel prior to plating, however, may require exposing the steel to acids and alkalies. During these operations, excessive amounts of hydrogen may evolve which may damage steels susceptible to hydrogen embrittlement. Steels that are susceptible to hydrogen embrittlement should be heat treated to remove hydrogen. The time required may vary from 8 to 24 hr depending on the type of steel and the amount of hydrogen to be removed. The temperature is of the order of 205° Hydrogen Embrittlement C (400° F), and the exact temperature may be alloy dependent. NICKEL ELECTROFORMING Nickel electroforming is electrodeposition applied to the production of metal prod- ucts. It involves the production or reproduction of products by electroplating onto a mandrel that is subsequently separated from the deposit. It is an extremely use- 229

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