Yes. Each passenger is allowed a maximum of five pieces or 100 kg (paid excess baggage ) at a time.
To purchase excess baggage login to Manage Booking (you will require PNR/ticket number/FFP number and passenger's last name).
Once you retrieve your booking, then click on "Purchase Excess baggage" on the right panel to purchase excess baggage online.
For other enquiries contact your local offices, contact details can be found in the following link https://www.qatarairways.com/en/worldwide-offices.html