There are very similar between over-molding and 2k injection molding, simply explain there is two point difference.
1, overmolding is using normal injection molding machine to produce the parts, which means move the first part (substrate part) to the second mold to mold to get the final part. 2K injection molding is using the 2K injection molding machine to produce two or three materials (colors), molding process is simple and fast.
2, compare to overmolding and 2k injection molding, 2k injection molding has high quality and high production efficiency, but since the 2k injection molding machine is too expensive, so sometimes use over-molding to replace it.
Blow is the relation to overmolding and 2k injection molding.