Carl D. Lundin

Power generation industry materials and their weldability

Abstract The development and use of modern materials for the power generation industry for the 1990s and beyond is discussed together with several important aspects of their weldability. The need for additional base material research is highlighted along with the pressing need for the simultaneous evolution of filler metal.

A Historical Perspective on Varestraint Testing and the Importance of Testing Parameters

This paper provides a historical perspective on the development of the Varestraint testing method as well as the design of a new Varestraint testing machine, utilized on a daily basis in the aerospace industry to solve hot cracking issues in production. The paper also discloses the importance in choosing the right testing parameters in order to minimize scatter in test results and to be able to make a reliable judgment in susceptibility towards hot cracking. Weld current, weld speed, bending rate and strain level as well as the evaluation procedure with i.e. measurement errors are included in the analyses.

Materials and Their Weldability for the Power Generation Industry

The development and utility of modern materials for the power generation industry for the 1990’s and beyond is discussed together with their weldability The need for additional base material research is highlighted along with the requirements for filler metal evolution.

CRYO-CRACKING : A TECHNIQUE FOR CREEP DAMAGE ASSESSMENT IN HIGH TEMPERATURE COMPONENTS

The characterisation of fracture surfaces of service exposed SA welds created under cryogenic conditions leads to a new fractographic analysis method called “Cryo-Cracking”. The “Cryo-Cracking” method takes advantage of an ability to separate the previous (service) creep damage from the “Cryo- Cracking” induced fracture features. This allows the evaluation of cavities and service damaged grain boundaries and permits a quantitative definition of damage level; aided by the SEMs high resolution and enhanced depth of field. In addition, directed EDS can provide chemical information regarding cavitation and the particulates which nucleate cavities. The “Cryo-Cracking” method does not depend on personal metallographic skills and is thus considered less sensitive to misinterpretation due to specimen preparation techniques.

Microstructural Investigation of the Weld HAZ in a Modified 800H Alloy

Detailed metallographic investigations of Gleeble simulated HAZ samples in modified 800H were performed. Precipitate dissolution, grain growth, HAZ liquation and the hardness degradation behavior in modified 800H were also addressed. Results of this study agree with previous HAZ hot cracking and softening behavior evaluations.Copyright