This paper presents the influence of nitrogen fluid phase on surface heat transfer coefficient in cryogenic machining. A novel optical nitrogen phase sensor is presented for characterizing the cryogenic fluid phase. Surface heat transfer coefficient was established experimentally, with the support of a new heat transfer model for cryogenic machining. Finite element models are developed with experimental data for Inconel 718, simulating the process behavior with varying nitrogen phases. Desired fluid phase at the delivery is found to be the key for achieving truly sustainable cryogenic machining
