What is a request to replace something within the IT infrastructure called?

A request to replace something within the IT infrastructure is called Request for Change. A Request for Change (RFL) is a formal request to implement a change, and is the first step taken before creating a Change Record.

The RFL includes all information needed for the team to approve and implement a change, ranging from a low to high level of detail depending on what the change request is. In the case of a large change request, the RFL often acts as a type of 'Project Charter,' where it is the overarching plan guiding multiple projects.