As-cast and Q+T. In as-cast condition, slight scratches are visible on Austenite matrix.
Q+T condition: Note the carbide particles precipitated, from tempered Martensite, after tempering.
Metal diffusion between ductile iron (3.90%C, 0%Cr) and AISI D2 (1.50%C, 12%Cr) steel .
Chrome and Carbon atoms migrated across the interface in opposite directions.
Metal diffusion between ductile iron melt and 10C (0.10%C) steel sheet.
QT iron melt with C% of 3.90% was poured at 1450C. 10C steel sheet was then carburized by QT melt.
Hypereutectoid composition is obtained at surface of 10C steel sheet.
Carbon % gradient is seen from surface to center of steel sheet.
On the QT side and adjacent to the interface, there is a thin layer of Pearlite without graphite nodules in it.
This layer is called "diluted layer" in which C% is not high enough to promote crystalization of graphite nodules.
Photos were shot with digital camera (數位相機) at the resolution of 1600x1200 pixels and down-sized to 640x480 for uploading.
Microscope used is Olympus GX 51 as mentioned previously in my posts.
Diffusion was blocked at "no diffusion zone" by chrome oxide (氧化物) which is not visible even under optical microscope. It was a test done some 3 yrs ago, trying to make composite steel plate.