The paper reports on a phase transformation in sputtered Ti-SS (stainless steel) alloy film during its plasma nitriding. First, it is shown that a Ti-SS film containing of about 9.5 wt.% of Fe is, when magnetron sputter deposited at low substrate temperatures below 100 degrees C, a high-temperature cubic beta-Ti phase film. A formation of high-temperature structure is due to a 'mixing effect', i.e., to an addition of Fe to Ti. During plasma nitriding of high-temperature cubic P-TI phase film, an opposite process takes place. The amount of Fe in the Ti-SS film reduces due to a formation of iron nitride gamma'-Fe4N. A depletion of Fe in the Ti-Fe alloy results in a phase conversion. The high-temperature cubic P-Ti phase converts into a low temperature hexagonal cr-Ti phase when the amount of Fe decreases below a minimum value necessary to sustain a high temperature structure of Ti-SS alloy film. The plasma nitriding was carried out in an anomalous glow discharge in a mixture of N-2 + H-2 at the total pressure 1067 Pa for 2 h at 550 degrees C.