Creating an effective and reliable field electron emission cathode is an important task of vacuum electronics. Field emission from massive cathodes made of industrial graphite was considered in this work. During the experiments, traditional current-voltage characteristics were obtained for the samples, long-term tests were carried out, and cathodes were exposed to argon ions. Carbon cathodes demonstrated emission current of hundreds microamperes and were able to successfully operate at pressure up to 2· 10-2 Pa. Such experimental conditions resulted in degradation of cathodes emission properties. For each stage of study the ion flux and electric field enhancement factors were calculated and analyzed. The best emission properties were shown by the sample with the lowest ash content and the largest grain size - GMZ graphite.