离子辐照对不同Nb含量CrNb涂层结构和力学性能的影响

Effect of Ion Irradiation on Structure and Mechanical Property of CrNb Coating with Different Nb Contents

利用能量为6 MeV、注量为2.3×10^(15)Au/cm^(2)的Au离子对磁控溅射法制备的Cr和CrNb涂层进行离子辐照。采用XRD、SEM及TEM等分析技术研究辐照对4种不同Nb含量的涂层微观结构和力学性能的影响。结果表明:随着Nb含量增加,晶格畸变导致衍射峰偏移,晶体转变为非晶,经离子辐照后涂层相结构出现了结晶现象。辐照令4种涂层表面形貌更光滑,同时TEM分析发现辐照区域微观组织结构变化不明显,表现出良好的抗辐照性能。Nb元素加入到Cr基涂层中,能提高涂层硬度模量和塑性变形能力,其中Cr_(0.92)Nb_(0.08)涂层具有最大值(硬度13.7 GPa、弹性模量204.2 GPa),经过离子辐照后的涂层均表现出较沉积态更高的硬度模量,这是辐照硬化导致。Cr基涂层中加入Nb元素能增加涂层力学性能,并未降低涂层的抗辐照性能,同时Cr_(0.82)Nb_(0.18)涂层在4种涂层中的抗辐照性能较好。

After the Fukushima nuclear accident,the concept of accident-tolerant fuel(ATF)was proposed.ATF can resist coolant loss accidents for a long time,while maintaining or improving the performance under normal conditions.Coating the surface of zircon fuel cladding is an important strategy for the development of accident resistant fuel cladding.Due to its advantages of high melting point,high thermal conductivity,good mechanical properties and high binding force with zirconium alloy,as well as excellent oxidation resistance and corrosion resistance induced by self-passivation ability,the pure Cr metal coating has become one of the most promising candidate materials in the field of ATF zirconium cladding.Before and during nuclear fuel operation or under accident conditions,the pure Cr coating is prone to breakage and cracking.The properties of Cr coating can be improved by adding Al,Ni,V,Nb and other metal elements.It provides a potential strategy to improve the comprehensive performance of Cr coated zirconium alloy coating.CrNb alloy coatings with different Nb contents were deposited on Zr alloy substrate with length of 10 mm×width of 10 mm and thickness of 1.5 mm by magnetron sputtering.During magnetron sputtering,the vacuum of the chamber was less than 5×10^(-3)Pa,the deposition temperature was kept at about 300℃,the argon gas flow rate was fixed at 55 sccm,and the sputtering pressure was fixed at about 0.5-0.6 Pa.By changing the area ratio of Cr and Nb,four coatings Cr,Cr_(0.92)Nb_(0.08),Cr_(0.82)Nb_(0.18)and Cr_(0.63)Nb_(0.37)were finally obtained.Due to the difference in sputtering rate of different elements,the thickness of all coatings is about 7μm,which is controlled by deposition time.Ion irradiation of Cr and CrNb coatings prepared by magnetron sputtering was carried out using Au ions with energy of 6 MeV and injection amount of 2.3×10^(15)Au/cm^(2).The effects of irradiation on the microstructure and mechanical properties of four Nb coatings were investigated by XRD,SEM and TEM.The results show that with the increase of Nb content,lattice distortion leads to diffraction peak shift,crystal changes to amorphous,and the phase structure of the coating is crystalline after ion irradiation.The surface morphology after irradiation is smoother and flatter than that under deposition,and the four coatings show excellent irradiation resistance.The hardness and elastic modulus of the deposited coatings increase first and then decrease with the change of Nb content,and the maximum value is Cr_(0.92)Nb_(0.08)coating(with hardness of 13.7 GPa and elastic modulus of 204.2 GPa),and the plastic deformation ability is improved.The addition of Nb content is beneficial to improve the mechanical properties of Cr coating.After the ion irradiation experiment,the hardness modulus and H/E and H^(3)/E^(2)of the coating increase as a result of irradiation hardening,and the H/E and H^(3)/E^(2)of the coating before and after the irradiation of Cr_(0.82)Nb_(0.18)have the smallest changes.Therefore,the irradiation resistance of the coating samples prepared is relatively good,and the addition of Nb element to Cr coating does not reduce the irradiation resistance of the coating.