Mechanical properties of 422 stainless steel repaired via wire feed laser welding

Abstract

Laser welding with filler wire additions could be used in restoration of components that are of high cost or sometimes difficult to procure, such as steam turbine blades in fossil fuel power plants. In the present work, machined V groove specimens were employed to simulate laser repair of Carpenter 636 stainless steel (SS), which has a similar composition to a blade material, type 422 SS. Before repair welding, a heat treatment procedure including solution and temper treatments of the specimens was carried out according to the mechanical and microstructural analyses of a used blade after 20 years service at about 540° C. Tensile, impact, and fatigue crack growth tests of weld repairs using 410 SS filler wire were conducted. The weld repairs exhibited an impact toughness similar to that of the base metal and a lower fatigue crack growth rate than the base metal. However, the lower hardness associated with 410 SS filler metal led to tensile fracture in the weld metal of repaired specimens. Accordingly, the use of 410 SS filler metal for repair welding type 422 SS components should be limited to regions under low stress.

Keywords

STAINLESS STEEL LASER WELDING STEAM TURBINES

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