Enhanced Erosion-Corrosion Resistance of Tungsten by Carburizing Using Spark Plasma Sintering Technique.

Yan Jiang,Qianfeng Fang,Junfeng Yang,Zhuoming Xie

doi:10.3390/ma13122719

Abstract

The biggest obstacle for the application of tungsten as the target materials in the spallation neutron source is its serious corrosion in the coolant of flowing water. For this reason, W–Cr–C clad tungsten was developed by tungsten carburizing in a spark plasma sintering device, with superior corrosion resistance in the static immersion and electrochemical corrosion test. This work focused on its erosion and corrosion performance in a flowing water system, based upon test parameters simulated under the service conditions. W–Cr–C clad tungsten showed superior corrosion resistance to that of bare tungsten due to the corrosion form changing from the intergranular corrosion of bare tungsten to pitting corrosion of W–Cr–C coating. The corrosion rate of tungsten was as high as tenfold that of the coated sample at 20 °C, and at most fourfold at 60 °C after testing for 360 h. Effects of water velocity and temperature on pitting and intergranular corrosion were investigated in detail and their corresponding corrosion mechanisms were analyzed and discussed.

Highlights

Tungsten is being chosen as the most favorable spallation target material for the spallation neutron source (SNS) due to its obvious advantages including high melting point, high neutron yield, and superior thermal conductivity [1,2]
The morphology, compositions, and phase distribution of the coated sample were characterized by the electron backscatter diffraction (EBSD) system
Close to the carbon and chromium-rich zone, tungsten carbide reached stoichiometry WC with an average grain size of 800 nm (Figure 2c,d), and chromium carbide is indexed as Cr7 C3

Summary

Introduction

Tungsten is being chosen as the most favorable spallation target material for the spallation neutron source (SNS) due to its obvious advantages including high melting point, high neutron yield, and superior thermal conductivity [1,2]. To improve the corrosion resistance, tungsten cladding with high temperature and corrosion resistance coatings have been developed as a target material such as HIPed tantalum-clad tungsten [7,8]. It suffers from issues of interface defects [7] and the high decay heat of tantalum [8,9]. The development of binder-free tungsten carbide coatings needed to solve two problems: density and brittleness To this end, carburizing by spark plasma sintering (SPS) technology was employed to produce tungsten carbide coatings on tungsten [17]. SPS is a high-temperature and fast-process sintering technique that provides a fast heating/cooling rate, short consolidation time, and controllable pressure, having been widely used in densification fabrication of nanomaterials, Materials 2020, 13, 2719; doi:10.3390/ma13122719 www.mdpi.com/journal/materials

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Discussion

Conclusion