Mechanical Properties of steel P91 and steel 12X1812T in dissimilar pipe welds used in boiler components

Abstract

The various welded joints used in production, most often in piping systems, always represent a special critical place in the system itself, seen in terms of possible occurrences of damage (defects). In the case of welding various joints of low-alloy and high-alloy steels, problems often arise due to the choice of additional materials, because the additional material according to the carbon content may more suit only one of the steels in the joint, usually the lower grade. The selected additive material, on the other hand, determines the properties of the welded joint, because it dictates the development of specific metallurgical processes in welding in which certain phases take place, which in turn are characterized by certain properties. The experimental investigation was made of dissimilar metal weld (DMW) joints between martensitic steel type P91 and austenitic steel type 12X18H12T using ERNiCr-3 filler metal. The as received P91 steel has been buttered using ERNiCr-3 filler metal, subjected to post weld heat treatment (PWHT) at 760°C for 120 min followed by air cooling and then welded with steel 12X18H12T by tungsten inert gas welding process without any PWHT after welding. Mechanical properties (tensile strength and hardness) and microstructure were investigated on the welded joints.