nChartControl1.Serializer.SaveControlStateToFile("C:\\SOMEFILE.TMP", Serialization.PersistencyFormat.Binary, null);

MemoryStream stream = new MemoryStream();
nChartControl1.Serializer.SaveControlStateToStream(stream, Serialization.PersistencyFormat.Binary, null);

You can also take a look at All Examples\Serialization as well as in the documentation:

http://helpdotnetvision.nevron.com/UsersGuide_Serialization_Serializing_the_Control_State.html

That describes the serialization support in detail. Let us know if you have any questions.