FUNCTIONALLY GRADED COMPOSITIONAL CONTROL METHODS TO ELIMINATE DISSIMILAR METAL WELDS (DMWs) DURING MANUFACTURE OF INTEGRAL HEADERS

摘要

A method of manufacturing a header assembly having a header section and a tube section includes the steps of providing a reverse mold of the header assembly, forming the header section by filling a header section of the reverse mold with an atomized low alloy steel powder, and forming the tube section. The tube section is formed by filling a first portion of a tube section with an atomized low alloy steel powder, forming a transition region by filling a second portion of the tube section with a series of atomized steel powders incrementally from a low alloy steel to an austenitic stainless steel, and filling a third portion of the tube section with an atomized austenitic stainless steel powder. The method further includes the step of consolidating and melting the atomized powders in a high temperature, high pressure atmosphere.