The mechanical behavior of a cast form of an advanced austenitic stainless steel, CF8C-Plus, is compared with that of its wrought equivalent in terms of both tensile and creep-rupture properties and estimated allowable stress values for pressurized service at temperatures up to about 850°C. A traditional Larson-Miller parametric model is used to analyze the creep-rupture data and to predict long-term lifetimes for comparison of the two alloy types. The cast CF8C-Plus exhibited lower yield and tensile strengths, but higher creep strength compared to its wrought counterpart. Two welding methods, shielded-metal-arc welding (SMAW) and gas-metal-arc welding, met the weld qualification acceptance criteria in ASME BPVC Section IX for the cast CF8C-Plus. However, for the wrought CF8C-Plus, while SMAW and gas-tungsten-arc welding passed the tensile acceptance criteria, they failed the side bend tests due to lack of fusion or weld metal discontinuities.

This paper presents a judicious reasoning method by coupling passive voltage contrast (PVC) with scanning probe microscopy (SPM) for revealing particular invisible defect modes, which were imperceptible to observe and very difficult to identify by means of traditional physical failure analysis techniques. In order to certify this compound method, it is applied to an implant issue as a case study. Through solving this particular defect mode, whose exact failure position could not be determined even with the most sensitive PVC or high-resolution SPM current mapping, the procedures and contentions are illustrated further. The significance of the reasoning method is based on electrical characterization and differential analysis. By coupling PVC with SPM, the capability to identify tiny defects is not limited to just distinguishing leakage or high-resistance under contacts. PVC can detect abnormal N+ contacts due to improper implanting, and SPM can provide the precise electrical characteristics.