Reactive sputter deposition of chromium nitride coatings

The effect of substrate temperature and sputtering gas composition on the structure and properties of chromium-chromium nitride films deposited on C-1040 steel using r.f. magnetron sputter deposition was investigated. X-ray diffraction analysis was used to determine the structure and the composition of the films. The average grain size of the films was determined using the full width at half-maximum method (or Scherrer's formula) from the X-ray diffraction pattern. Films were deposited at temperatures ranging from room temperature to 400 degrees C. At 200 degrees C all the films consisted of a single phase, while at 400 degrees C dual-phase films were observed at certain partial pressures of nitrogen. Microhardnesses of the films were evaluated from the composite hardness (substrate with films on it) values using a physical model. At 200 degrees C, the hardness of the films was seen to increase with increasing nitrogen content in the sputtering gas as a result of the hard Cr-N phase formation. At higher deposition temperatures, the residual stresses lead to spalling of film.