Abstract
With synergy of plastic deformation near crack tip and pulse current treatment, complex phase transformation and recrystallization occur in the metallographic structure, with the austenite transforming to fine grain structure and deformation-induced martensite; but, without the plastic deformation, the phase transformation, and recrystallization it was difficult for the crack arrest process to take place only undergoing the pulse current treatment. The nano-indentation experiment showed that the phase transformation region contained the maximum residual compressive stress consisting of four parts: the plastic stress, the explosion stress, the thermal stress, and the transformation stress, which was beneficial to restrain the crack growth. However, the solidification structure and the deformation-induced martensite structure was vulnerable to pitting corrosion through scanning microelectrode technology (SMET) and pitting corrosion experiment, but the pitting corrosion resistance could be improved through the solution heat treatment.
Highlights
Crack is one of the most common failure modes of metal components, frequently leading to serious accidents and damages
According to the theory of fracture mechanics, a plastic zone would be formed near crack tip in the process of crack growth, which had a significant influence on the metallographic transformation and the corrosion property of austenitic stainless steel
If the crack tip of 304 stainless steel existed in plastic zone, the metallographic structure would
Summary
Crack is one of the most common failure modes of metal components, frequently leading to serious accidents and damages. Mechanism of the metallographic transformation is unclear in the heat affected zone near crack tip in the crack arrest process. Corrosion resistance of materials, especially austenitic stainless steel, near crack tip has been rarely reported after the pulse current treatment. According to the theory of fracture mechanics, a plastic zone would be formed near crack tip in the process of crack growth, which had a significant influence on the metallographic transformation and the corrosion property of austenitic stainless steel. Optical microscopy (OM), scanning electron microscopy (SEM), nano-indentation, SMET were used to study the microstructure, residual stress, and pitting corrosion near crack tip of 304 stainless steel specimens with plastic zone or non-plastic zone after the pulse current treatment. The reasons for change of the pitting corrosion resistance in different micro-zones near crack tip were discussed
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