STUDY ON DESCALING CHARACTERISTICS OF 304 STAINLESS STEEL USING PICKLING AND ABRASIVE WATER JET

Abstract

The variability in the surface integrity, mechanical properties and corrosion resistance of the surface layer of 304 stainless steel after scale removal by pickling and an abrasive water jet, removing the oxide and Cr-poor layer was studied comparatively. It was found that the surfaces of the pickling specimens were etched with pits of varying sizes, with Ra of 4.384 µm and Rz of 24.81 µm, while the surface microhardness fluctuated in a range of 200–220 HV. The surfaces of the abrasive water jet specimens exhibited a stack laminar characteristic, Ra of 3.960 µm and Rz of 22.63 µm, while the surface microhardness decreased with an increase in the distance from the surface; the surface microhardness increased from the original 210 HV to 380–390 HV, producing a 1-mm deep work-hardening layer, which had a great impact on the microhardness of the substrate 0–0.3 mm from the surface. For both the pickling specimens and the abrasive water jet specimens, the material tensile strength and yield strength were slightly increased, and the elongation after fracture was significantly reduced. The corrosion resistance of the pickling specimens was better than that of the abrasive water jet specimens. The surface layer of the AWJ specimens generated a Cr-poor layer due to severe secondary oxidation, and the corrosion resistance of the material was reduced.