As a freshman in 2020, Hartwig played in six games while making three starts en route to being named a Big Ten Conferencehonorable mention. In 2021, he started all 13 games for the Boilermakers. Ahead of the 2022season, Hartwig was named to the Rimington Trophywatchlist. That season, he started 11 games for the Boilermakers before suffering an injury. In 2023, Hartwig started nine games after missing the first three due to an injury from 2022, once again earning an all-Big Ten honorable mention.