Combined effect of rapid nitriding and plastic deformation on the surface strength, toughness and wear resistance of steel 38CrMoAlA

B Wang,W T Fu,Z Q Lv,S H Sun,X Huang,Z A Zhou

doi:10.1088/1757-899x/89/1/012046

Abstract

The combined treatment of pressurized gas nitriding and cold rolling is proposed as a new approach to rapid preparation of a strong and tough nitrided layer for steel 38CrMoAlA. The microstructural characteristics and properties of the modified surface layer in comparison with those of the conventionally gas nitrided sample have systematically been evaluated. The results show that the hardness and toughness of the nitrided surface layer can be significantly improved by the combined treatment. Especially, the wear resistance of nitrided surface layer under heavy loads was greatly enhanced. It can provide a new approach to rapidly preparing a nitrided layer with high strength and toughness.

Highlights

Gas nitriding (GN), one of the well-established commercial surface modification techniques, has been widely used for improving the mechanical properties and wear/corrosion resistance of alloys and steels [1,2,3]
After the pressurized gas nitriding (PGN) treatment at 530°C under 5 atm for 5 h, the nitrided surface layer almost consisted of αN phases except for a very small amount of γ′-Fe4N phase (Fig. 1d), which was consistent with the optical microscopy (OM) observation of the PGN sample (Fig. 1c)
The above results demonstrated that a compound-free nitrided layer can be rapidly prepared by PGN with a controlled nitriding potential, which was obtained through adjusting the nitriding pressure and ammonia flow rate

Summary

Introduction

Gas nitriding (GN), one of the well-established commercial surface modification techniques, has been widely used for improving the mechanical properties and wear/corrosion resistance of alloys and steels [1,2,3]. Compared with the diffusion layer, the compound layer consisting of a heterogeneous mixture of ɛ-Fe2-3N and γ′-Fe4N phase, is very thin and contains high internal stresses, so that the nitrided surface layer is friable and brittle [4,5,6,7,8,9]. This will affect the performance of the nitrided components subjected to severe service environments involving high shear, compressive and impact loading conditions [4,5,7]. Some methods of nitriding such as two-stage GN and controlled GN with the nitriding potential below the critical value were

Methods

Results

Conclusion