The creep enhanced low alloy steel with 2.25Cr-1.6W-V-Nb (HCM2S; Gr.23, ASME CC2199) has been originally developed by Mitsubishi Heavy Industries, Ltd. and Sumitomo Metal Industries, Ltd. The steel tubes and pipe (T23/P23) are now widely used for fossil fired power plants all over the world. Recently, the chemical composition requirements for ASME Code of the steel have been changed and a new Code Case 2199-4 has been issued with the additional restriction regarding Ti, B, N and Ni, and the Ti/N ratio incorporated. In this study, the effects of additional elements of Ti, N and B on the mechanical properties and microstructure of T23/P23 steels have been evaluated. It is found that N decreases the hardenability of the steel by forming BN type nitride and thus consuming the effective B, which is a key element for hardening of the steel. The addition of Ti, on the other hand, enhances the hardenability of the steel by precipitating TiN and thus increasing the effective B. It is also found that too much addition of Ti degrades the Charpy impact property and creep ductility of the steel to a great extent. This phenomenon might affect the steel's long-term creep rupture properties, although a steel with the original chemical composition has demonstrated high creep strength at temperatures up to 600°C for more than 110,000 h.

This study investigates the behavior of boron nitride (BN) inclusions in high-chromium ferritic heat-resistant steels like P92 and P122. Boron is added to improve creep resistance, but its role is not fully understood. Here, the formation and dissolution of BN inclusions during high-temperature heat treatment were examined. Microscopic analysis revealed coarse BN inclusions (2-5 μm) alongside smaller alumina inclusions. Annealing experiments showed that these BN inclusions only dissolved at temperatures exceeding 1200°C, suggesting they form during casting or forging processes below 1150°C. Chemical analysis identified a critical boron and nitrogen concentration threshold (below 0.001% B and 0.015% N) for BN inclusion formation.

Pin-point (specific area) planar transmission electron microscopy (TEM) analysis has been improved to study process-induced defects in recent very large scale integrated (VLSI) devices. The specimens are prepared by a combination of marking failure sites with focused ion beam (FTB) equipment and planar TEM specimen preparation technique. This method provides not only planar observation of localized failures with an accurate observation with high positioning accuracy but also wide range of observable area which is feasible to carry out some application techniques associated with TEM. In particular, it is found to be a powerful method to identify the nature of crystalline defects which cause the failures. This work presents the detailed procedure and demonstrates its successful applicability via studying a leaky bipolar transistor in 0.5μm BiCMOS devices (one failure of more than 4500 transistors). The results clarify the presence of stacking faults, formed during epitaxial growth, between collector and emitter regions in the specific transistor with resistive collector-emitter leakage current.