摘要
通过双层辉光等离子体表面渗金属方法,在难熔金属Mo、Nb表面成功制得Ir涂层,并对其微观结构和微观形貌进行分析.制得的铱涂层呈亮银白色,致密且表面均匀,无明显缺陷.XRD研究表明:Ir涂层呈多晶态,并沿(220)晶面优先生长,Nb基体上Ir涂层(220)晶面择优生长趋势明显高于Mo基体上Ir涂层(220)晶面择优生长趋势;Ir涂层由锥形晶构成,致密均匀,没有微观缺陷和微观裂纹.Ir涂层制备过程中,在基材表面形成了一个基材元素梯度分布的过渡层.过渡层的存在使得Ir涂层与基材结合良好;同时,Ir涂层遭受高密度离子轰击,在涂层内部产生高的残余压应力.利用纳米压痕仪测定了致密Ir涂层的硬度及弹性模量,并对其加载卸载曲线进行分析.由于基体热膨胀系数的差异,Nb基体上Ir涂层的残余压应力、表面硬度均大于Mo基体上Ir涂层.
Iridium （Ir） has low oxygen permeability up to 2 100 ℃ with the melting temperature of 2 440 ℃, good chemical compatibility, and an effective barrier to oxygen diffusion. Ir coaling had been taken as the promising oxi- dation protection of the refractory materials to provide even higher service temperature and longer service life. Ir coating could be prepared through various techniques, such as metal organic chemical vapor deposition, chemical va- por deposition, D.C. or R. F. magnetron sputtering and pulsed laser deposition. The double glow plasmas technique is a novel technique to prepare metals coating. The novelty of this technique is coating elements can inter into the substrate to form a buffer layer with the coating concentration distributed gradiently along the depth of the buffer layer, In this research, Ir coating was obtained on the surface of Mo and Nb substrate by double glow plasmas tech- nique, Ir coating seemed to be light silver-white, and no any surface defects through macrography. Microstructure and morphology of the as-prepared Ir coating was examined by the X-ray diffraction and scanning electron microsco- py, respectively. The experimental results indicated that the iridium coating had a poly-crystalline structure with preferential growth orientation of （220） crystal plane. The trend of （220） preferred orientation on Nb substrate was the higher than that on Mo substrate. The Ir coating was rough and composed of the tapered crystallites, but no evi- dence of cracks or other defects. A buffer layer was formed between the pure Ir coating and the Mo （Nb） substrate during the forming of the Ir coating. The Mo （Nb） concentration distributed gradiently along the depth of the buffer layer, which resulted to the highly adherent Ir coating. Because of the bombardment of the high density hybrid ions. the intrinsic growth stress （compressive） was generated in Ir coating. The surface micro-hardness, elastic modulus and the load-depth curve of the Ir coating were measured by nano-indentation instrument. The residual compressive stress and the surface micro-indentation on Nb substrate were higher than those on Mo substrate, which was caused by the difference of the coefficient of thermal expansion between the Ir coating and the substrate. The trend of hard- ness, elastic modulus of the Ir coating on Mo/Nb substrates was consistent to the residual stress and the crystal ori- entation.
出处
《南京大学学报（自然科学版）》
CAS
CSCD
北大核心
2009年第2期234-240,共7页
Journal of Nanjing University（Natural Science）
基金
国家自然科学基金(50872055/E020703)
关键词
双辉等离子
难熔金属
铱涂层
表面形貌
显微结构
残余应力
double glow plasma, refractory metals, lr coating, surface morphology, microstructure,residual stress
