Failure analysis of heat exchanger tubes of Ni-200 alloy in a titanium tetrachloride vaporizer

Document Type : Original Article

Authors

1 Metallurgical and Materials Engineering Department, Faculty of Petroleum and Mining Engineering, Suez University, 43721 Suez, Egypt. - Department of Environmental Engineering, College of Engineering at Al-Lith, Umm Al-Qura University, Saudi Arabia.

2 Metallurgical and Materials Engineering Department, Faculty of Petroleum and Mining Engineering, Suez University, 43721 Suez, Egypt - Department of Environmental Engineering, College of Engineering at Al-Lith, Umm Al-Qura University, Saudi Arabia.

3 Cristal Global, KSA

Abstract

This paper presents a metallurgical analysis of damage occurred in heat exchanger tubes of nickel alloy (Ni-200) used for vaporizing titanium tetrachloride (TiCl4). The tubes had undergone a dual environmental condition with heating water steam inside and liquidous TiCl4 outside. Several investigations were conducted to identify the potential failure mechanism. Such investigations included visual examination and microstructural characterization via optical microscopy and scanning electron microscopy (SEM) equipped with energy dispersive X-ray analyzer (EDX). Investigations extended also to the mechanical characterization of the tube materials through hardness and tensile testing. The results of hardness and tensile tests showed that the bent tubes had sustained strain hardening, which can act as potential sites of corrosion. SEM and EDX investigations revealed that the damaged sections had corrosion product layers rich in sulfur. However, Cavitation corrosion was found to be the main corrosion form shown in the damaged tubes. It is recommended to keep TiCl4 liquid at high pressure values so that the vapor bubbles are not formed. Also, the sulfur content in the TiCl4 must be kept at very low levels.

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