Integrated welding and thermal processing joining method for creep strength enhanced ferritic steels

A method of forming a weld comprising the steps of:

• providing a first surface of a carbon steel;
• providing a second surface of a weldable alloy;
• positioning said first surface adjacent to said second surface;
• welding said first surface to said second surface by applying a first heat source to said first surface and said second surface to heat said first surface and second surface to a sufficiently high temperature above their melting points to form a weld;
• cooling said weld to below the martensitic start temperature of said carbon steel but before said weld cools below said first surface's martensitic finish temperature;
• tempering said weld subsequent to said step of cooling, said tempering including heating said weld at a rate of 10° C. per second or greater to above said first surface's martensitic start temperature but to not above the austenitization temperature of said first surface;
• maintaining the weld at a temperature between said first surface's austenitization start temperature and martensitic start temperature for a sufficient amount of time to transform the weld and heat affected zone of said first surface into tempered martensite;
• and
• cooling said weld at a rate of 15° C. per minute or greater after transforming the weld and heat affected zone of said first surface into tempered martensite.