Nitriding of AISI M2 tool steel in an inductive r.f. plasma

Abstract

The nitriding of AISI M2 tool steel in an inductive r.f. plasma was investigated. The plasma was sustained with a 27.12 MHz generator in gas mixtures of N 2 and H 2 at a pressure of 10 mbar. The ion nitriding was performed at a net r.f. power of 400 W at substrate temperatures of 450–500 °C. X-ray diffraction studies of the treated samples revealed that the most efficient formation of nitride phases was observed in samples nitrided in a pure N 2 plasma. As a result of the ion nitriding the surface hardness was substantially increased from a Vickers hardness VHN of 290 kgf mm -2 for untreated samples to a maximum VHN of 1200 kgf mm -2 for samples treated in a plasma sustained in a gas mixture with N 2:H 2 = 1:1.