IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Engineering Monday Sessions
       Session SE-MoP

Paper SE-MoP8
The Effect of Cooling Conditions on Plasma-Carbonitrided Iron Surfaces

Monday, October 29, 2001, 5:30 pm, Room 134/135

Session: Poster Session
Presenter: P.A.P. Nascente, Universidade Federal de Sao Carlos, Brazil
Authors: L.C. Gontijo, Universidade Federal de Sao Carlos, Brazil
R. Machado, Universidade Federal de Sao Carlos, Brazil
E.J. Miola, Universidade Federal de Sao Carlos, Brazil
L.C. Casteletti, Universidade de Sao Paulo, Brazil
P.A.P. Nascente, Universidade Federal de Sao Carlos, Brazil
Correspondent: Click to Email
Plasma- carbonitriding has been used to improve the tribological and mechanical properties of materials, specially iron-based alloys. In this work, the Pulsed Glow Discharge (PGD) technique was employed for carbonitriding pure iron. This method is more economical than others because it provides for faster nitrogen and carbon diffusion, which in turn allows for lower processing temperatures and shorter treatment times with satisfactory results. Three sample sets were carbonitrided in a gas mixture of 2 vol. % CH@sub 4@, 20 vol. % N@sub 2@, 78 vol. % H@sub 2@, under a pressure of 400 Pa, discharge frequency of 9 kHz, temperature of 580 °C, during 90 minutes. The first sample set was cooled under vacuum, the second set, under air, and the third set was quickly removed from the furnace and then quenched in oil. The three sample sets were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). For the samples cooled under vacuum, the diffusion zone comprised of enlongated needle-like precipitates and shorter ones, which were identified as @gamma@'-Fe@sub 4@N and @alpha@"-Fe@sub 16@N@sub 2@, respectively. The same phases were also observed in the diffusion zone of the samples cooled under air. However, these phases were not detected in the samples quenched in oil. The compound layer for the three sample sets consisted of @gamma@'-Fe@sub 4@N and @epsilon@-Fe@sub x@(N,C). An austenite (@gamma@) transformed zone was detected in between the compound layer and the diffusion zone.