Zhang Borui,Chen Jintong,Xu jinlong,et al.Effects of Temperature and Atmosphere on the Isothermal Decarburization Behavior of GCr15 Steel[J].Special Steel,
Zhang Borui,Chen Jintong,Xu jinlong,et al.Effects of Temperature and Atmosphere on the Isothermal Decarburization Behavior of GCr15 Steel[J].Special Steel,DOI:.
Effects of Temperature and Atmosphere on the Isothermal Decarburization Behavior of GCr15 Steel
GCr15 is a typical representative of high-carbon chromium bearing steel, and surface decarburization can severely degrade its surface quality and service performance. This paper presents an experimental investigation and mechanism analysis on the isothermal decarburization behavior of GCr15 bearing steel in air, N₂+H₂+H₂O and N₂+H₂O atmospheres. The results show that in air atmosphere, no decarburization layer was observed at 700 ℃, a fully decarburized layer and a partially decarburized layer were observed at 800 ℃, and only a partially decarburized layer was present above 900 ℃. Compared with hypoeutectoid steel, GCr15 exhibits a decarburization layer covering a wide range of carbon content. Coupled with the strong sensitivity of room-temperature microstructure to the cooling rate after isothermal decarburization, the evolution of room-temperature microstructure in the decarburization layer with decarburization time is complex. The hardness method, rather than the metallographic method, is the preferred method for measuring decarburization depth. The total decarburization layer thickness increases with rising temperature and holding time, reaching 511, 690, 960, and 1 270 μm after isothermal treatment at 700, 800, 900, and 1 000 ℃ for 120 min respectively. In comparison with the N₂+H₂+H₂O atmosphere, the strong oxidizability of the N₂+H₂O atmosphere results in the oxidative ablation of the decarburized ferrite layer and even a certain proportion of the partially decarburized layer. The results of this study provide guidance for decarburization layer control during the thermal processing design of GCr15 steel.
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