In order to improve the high temperature performance of AISI 403 martensitic stainless steel, duplex surface treatment which
combines the methods of pack cementation chromizing and boronizing was carried out. Specimens were chromized at 1100 8C
for 2 h and were subsequently boronized in a solid medium consisting of EKabor-III powders at 950 8C for 9 h. The characteristics
of the duplex treated specimens were evaluated by a scanning electron microscopy, X-ray diffraction (XRD), glow discharge
optical emission spectroscopy and Micro-Vickers hardness testing. The chromizing for 2 h had created a Cr diffusion layer of
approximately 130 mmthickness. Subsequent boronizing on the Cr diffused layer induced formation of duplex layer of
approximately 50 mm thickness with a largely improved surface microhardness up to approximately 2300 Hv. The cross-sectional
microstructure of duplex treated specimen consisted of a duplex layer, a transition region between duplex layer and Cr diffusion
layer, a Cr diffusion layer and matrix in series. XRD analysis revealed that the various phases of FeB, Fe2B and CrB are present
in the duplex layer. The wear volume of duplex treated specimen after a wear test at 500 8C, comparing the duplex treated
specimen with the specimen treated only by boronizing, was reduced by a factor of 1.5. In addition, the duplex treated specimen
showed a much-improved high temperature oxidation resistance, which could be attributed to the high Cr content (f20 at.%).
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