Boeing Aircraft experienced excessive cracking and weld repair maintenance in very short periods of time with their 316 stainless steel salt pot heat treat baskets. The baskets are used to hold a variety of components including critical machined landing gear segments during hardening and tempering cycles. The cracking was believed to be caused by a combination of constant thermal cycling of the heavily welded baskets from 1800°F to 600°F and corrosion from the molten salt.
In their search for an improved material of construction, Boeing was looking for an alloy which would avoid catastrophic basket failure and subsequent loss of expensive machined components, reduce life-cycle cost by reducing extensive weld repair, and increase up-time and resultant capacity through the heat treat operation
Boeing selected HAYNES® 556® alloy and was pleased to note its availability from Haynes’ Service Center Stock.
HAYNES 556 alloy has nearly twice the strength of 316 alloy at 1600°F. Combined with its excellent ductility, thermal fatigue resistance is improved. Laboratory tests and field experience show 556 alloy to be equal to, or better than, nickel-base HASTELLOY® X alloy regarding resistance to molten chloride salts. In addition, as-welded ductility of 556 alloy is excellent.
Thus far, at comparable operating times, 556 alloy baskets have far outperformed 316 alloy baskets. Maintenance costs are down and reliability is increased. Can you afford not to consider HAYNES 556 alloy?
*Average of two tests for each condition