Revealing the critical failure factor and sub-surface damage mechanism of 316 stainless steel during fretting corrosion under the molten lead-bismuth eutectic

Abstract

The critical failure factor and damage mechanism of 316 stainless steel during fretting corrosion under the molten lead-bismuth eutectic (LBE) are specially investigated. Representative Fτ-D-cycle curves are shown to reflect the changing process and characteristics of different cycles for each parameter during fretting corrosion tests. The fretting operation regime is the mixed fretting regime (MFR) with minor stroke. The increase in stroke and temperature convert the fretting operation regime from MFR to the gross sliding regime (GSR). According to the dissipated energy and wear volume among all the samples, the results demonstrate more information as follows: the change of dissipated energy and wear volume is positively correlated with stroke, cycle number and temperature. The most serious damage occurred at 450 ℃− 80 µm-2 × 106 cycles. Multivariate linear regression model was established for 18 groups of data, and it was concluded that temperature was the key failure factor within the parameter range of this experiment. The first effect of temperature increase is to increase the rate of diffusion of Ni element into LBE, and the inevitable dissolution corrosion will occur. The problem is that a large number of vacancy defects are generated. The second effect of temperature increase is that the austenite substrate is transformed into ferrite, which cannot resist damage caused by fretting, due to the dissolution of large amounts of Ni.