An improved single-step catalytic oxidation process for the conversion of one or more C3 to C5 alkanes, in the presence of supercritical fluid, to one or more oxidation products, such as unsaturated carboxylic acids and unsaturated nitriles. This method for fabricating a stepped forged material comprises the following steps: a step for obtaining a primary forged material in which an austenite stainless steel billet is heated to 1000-1080\xb0 C. Subsequently, a sight glass structure is snapped into the sight glass opening to complete the installation of the doorburner assembly.