Creep Resistant Steels

[@wanghou6219]

Professor Bhadeshia. Would the metastable carbide strart to dissolve immediately when stable carbides begin to form?

[@bhadeshia123]

The reactions occur simultaneously rather than stepwise, albeit at different rates

[@KarthikIyerCoep]

Thank you Sir for sharing this video Regards, Karthik Iyer Welding Engineer

[@srivatsakulkarni1981]

Dear sir, I have a doubt. what is the significance of equicohesive temperature. To my understanding it is temperature at which strength of grain and grain boundaries are same. so consider the example of bainitic creep steels or martensitic steels these are widely used in power plant applications (~650°C). These steels inherently have fine grains when put in service. But literature says coarse grain favour creep deformation. so it means that the 650°C is the limiting temperature for the grain boundaries above this temperature grains have high strength ??. if not then why can't we use martensitic steels in gas turbine applications where service temperature is very high

[@bhadeshia123]

Afraid I do not know.

[@osgokul]

Its not that grains become stronger but grain boundaries become weaker. At high temperatures the grain boundary becomes weaker than the grain interior and two grains can slide past one another due to shear stress. The temperature at which the grain is as strong as the grain boundary is called the equicohesive temperature.

[@wanghou6219]

professor Bhadeshia: where can find the second part of this vedio?

[@bhadeshia123]

kzbin.info/www/bejne/jZOpn2pqhsiImNE