Is sweetened condensed milk a substitute for evaporated milk?
No.

Sweetened condensed milk has a 40% sugar content. It is very sweet, suitable for desserts and such. It is entirely too sweet to substituted into a curry. 

The consistency is drastically different. Evaporated milk is about the same consistency as heavy cream. Sweetened condensed milk, because of its high sugar content, is more the consistency of a warm caramel. 

Also, they are different colors, evaporated milk is white, sweetened condensed is light brown.