the us department of energy advanced research and technology development (ar&&td) fossil energy materials program in 1986 began a six-year activity to investigate candidate alloys fro advanced steam cycle superheaters and reheaters. the specific advanced austenitic alloys of interest were defined through a screening program which assessed strength and metallurgical stability within the temperature range of 650 to 760c. one task in the program addresses the fabrication of tubing from alloys containing controlled amounts of mc- carbide forming additions and the cladding or surface treating of tubing for optimum corrosion resistance. these alloys are members of a family of ht-ups (high-temperature, ultrafine precipitate) austenitic alloys. under the current research effort, a heat of 20cr- 30ni-mo (m800h) was successfully melted, cast, and hot rotary forged into billet stock. hot extrusion of wrought monolithic and alloy 690 and 671 clad m800h and lss was demonstrated. furthermore, cold tube- reducing of monolithic and alloy 690 clad m800h and lss was successfully demonstrated. alloy 671 clad composite hollows, however, could not be cold reduced because of a blocky carbide discontinuous network at the interface. monolithic and alloy 690 clad m800h and lss tubes were solution treated at 2175(degrees)f (1190c) and 5--10 cold worked. weld cladding of m800h and lss with alloy 690 or mig72 was successfully demonstrated. lss was also chromize surface-treated during this research effort. and, four laboratory heats of lss and m800h were modified to yield improved heat-affected zone li