The Duplicate Replacer app doesn't require Vault. But it does work very well with Vault. If you are using a new version of Vault Professional you have access to the Vault  Duplicate Search tool. 

The Vault Duplicate Search was added to paid versions of Vault starting with release 2020.2. It's a great tool that searches for duplicates against files already in the Vault only. Therefore if you have duplicate components in your active assembly in Inventor, you would need to use this long workflow to replace the duplicates cleanly if using the Vault tool only.

Vault-only workflow

1. Check In the entire assembly into Vault.
2. Wait for the Vault Job Processor to index the parts for duplicates….
3. Run the Vault Duplicate Search tool inside Inventor.
4. Right click on each part file in the duplicates list to replace it from Vault.
5. Clean up the Vault to remove the redundant parts that have been replaced.

We're big fans of Vault, for real.
But this duplicates workflow is far from ideal.

Vault and Duplicate Replacer Workflow
If you're not a fan of the workflow above, why not add The Duplicate Replacer alongside Vault and supercharge your workflow:
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1. Use The Duplicate Replacer to quickly scan the active assembly.
2. Use The Duplicate Replacer to replace all the duplicates (with any member of each group of duplicates) in seconds*.
3. Now you've cleaned up the assembly with respect to itself, use the Vault Duplicate Search tool to perform a check of your cleaned-up assembly against the Vault and replace from the Vault also, before checking in. Beautiful.

* Can take minutes on large (2K+ components) assemblies!