Using vacuum induction melting combined with inert gas protection

the occurrence and formation Law of the interfacial reaction between DZ22Bsuperalloy and Al

2

O

3

ceramic shell for investment casting were investigated with considering different melting temperature and contacted time.Moreover

the resultant surface sanding defect caused by interfacial reaction was also discussed.The results show that the Hf element in superalloys exhibits highly active

which is prone to react with Al

2

O

3

and the reaction product of HfO

2

is formed on the casting surface.With the contacted time of 15min

the interfacial reaction is enhanced with the increase of melting temperature.It is found that absence of interfacial reaction occurs at 1 400℃

and weak interfacial reaction is formed at 1 500℃

and then serious reaction can be expected at 1 600℃

accompanied with the sand sticking phenomenon.Due to the formation of physical permeability layer and the presence of stress concentration

the surface layer of ceramic shell is inclined to fall out.Most serious reaction can be observed with the contacted time of 30min and melting temperature of 1 600℃

where the reaction zone with the size of 1mm is formed on the casting surface.