Papers by Author: Yong Jiang

Abstract: In this paper, corrosion behaviors of 13MnNiMoR steel and its weld joint in the EO reactor service environment were studied. Metallographic analysis and electrochemistry corrosion tests in boiler water which are concerned on different zone metal of 13MnNiMoR steel weld joint have been carried out, and the effect of postweld heat treatment and the pH value of the working medium were discussed. The results indicated that the resistance of different zone metal in joint is tightly connected with their microstructure and heat-affected zone always shows the max corrosion current density. The results also showed that heat treatment could significantly improve the anticorrosion properties of 13MnNiMoR steel weld joint.

Abstract: In this paper, mechanical performance test, slow strain rate test (SSRT) and optical microscopy analysis were employed in studying the effect of carbon migration on sulfide stress corrosion cracking (SSCC) behaviors of Cr5Mo/A302/0Cr18Ni9 dissimilar joints. The results showed that the resistance to SSCC of this joint improved first then decline after 98h aging treatments. Optical microscopy analysis showed fracture located in coarse grain heat-affected zone (HAZ) of as-welded joint, while in the joints aged for 56h and 98h, the fracture position transferred from coarse grain zone of HAZ to carbon rich belt in welds.

Abstract: The difference in microstructures of the base metal (BM), weld metal (WM) and heat-affected zone (HAZ) in the weldment is one of the major reasons for the failure of the welded equipments, which can be essentially attributed to the non-homogeneous corrosion occurred electrochemically on the weldment. Therefore, it is necessary to explore the corrosion properties of weldment. In this paper, the electrochemical behavior of SPV50Q steel weldment was investigated. The polarization curves of BM, WM and HAZ in 5wt.%NaCl-0.5wt.%HAc solution containing H2S were measured by potentiodynamic polarization. Interface characterization was also conducted by electrochemical impedance spectroscopy (EIS). The results show the anodic curves are almost same regardless of various pH or H2S content, but the cathodic curves show some difference. Relatively large variation in corrosion current density (icorr) obtained by fitting technique exists among BM, WM and HAZ. icorr of WM and HAZ is larger than that of BM, and icorr of WM is maximum. According to EIS results, polarization resistance (Rp) increases in the orders of WM, HAZ and BM. It is concluded that WM and HAZ are less resistant to corrosion than BM, which can be correlated to the premature failure of the weldment serviced in H2S-containing environment such as sulfide stress corrosion cracking (SSCC) and /or stress oriented hydrogen-induced cracking (SOHIC) etc.

Abstract: This paper is aimed at investigating the damage and remaining life of a whole HP-Nb hydrogen reformer tube serviced for 12 years. The damage and remaining life evaluation of different parts of the tube were made using metallographic examination, ambient and high temperature uniaxial tensile tests, creep rupture tests and damage mechanics analysis. The results showed that different parts of the tube have the different damage and remaining life due to different service temperature, higher the service temperature, severer the damage and shorter the remaining life. Based on these research results, a case of local maintenance of the reformer tube was introduced.