Sync my husband's Exchange with my iPhone 7 plus
You add it just like you would an email account. you will need his email address, password and possibly the active directory domain name depending on that version of Exchange they have.


Tap settings, scroll down and tap Mail, Contacts, Calendars.
Tap Add Account...
Tap Microsoft Exchange
Enter the mail address and the password and tap next
If everything is copacetic you'll get green checkmarks and then the screen to choose what parts of the account you want to add.


In your case turn off everything except Calendars and tap save.

Some versions of iOS and Exchange will REPLACE the current contents of your calendar for it's own information. So you may want to back up your calendar on your Mac before you do this, just in case.

Or you could use the free iOS Outlook client. I use it for my work email, it's a good client and helps to keep my work and personal info separate.