摘要
本文采用双层辉光等离子表面冶金技术在Q235钢表面制备Ni-Cr合金层,通过扫描电子显微镜及能谱仪附件、X射线衍射仪、动态显微硬度系统等测试方法表征了合金层的组织形貌、化学成分、相组成、动态显微硬度和弹性模量,并采用CHI750电化学工作站,以304L不锈钢为对比试样,通过三电极体系以0.001V/S的扫描速度研究了两者在3.5%的NaCl和0.5%H2SO4两种介质中的电化学腐蚀行为.结果表明:等离子共渗后,Q235钢表面形成了厚度约12μm的镍铬合金层,渗层均匀致密,无孔洞裂纹等缺陷,其表面晶粒结聚成团,呈颗粒状.镍、铬合金元素由表及里呈梯度分布,并在次表层达到浓度高峰,其原因在于在此工艺下沉积的表层区域原子发生逆溅射和逆扩散.合金层主要由FeCr0.29Ni0.16C0.06、Cr23C6和γ相组成,与基体呈冶金结合,表面动态显微硬度达9.72GPa.电化学腐蚀试验表明合金层在NaCl溶液中的自腐蚀电位相对于不锈钢正移25mV,并且具有比不锈钢更小的腐蚀电流密度,而在H2SO4溶液中合金层的腐蚀电位虽负移9mV,但其腐蚀电流密度依然远小于不锈钢,计算得出其腐蚀速度相对于不锈钢分别降低了2.35倍和1.30倍,因此双层辉光等离子镍铬共渗可显著提高Q235的耐腐蚀性能.
In this paper, the nickel-chromium alloyed layer was prepared on Q235 steel by using Double Glow Plas- ma Surface Alloying Technology. The morphology and microstructure of the alloyed layer were observed by means of optical microscope （OM） and scanning electron microscope（SEM）. The concentration distributions of Nickel and Chromium were analyzed using the energy dispersive spectrometer （EDS） accessory. The composing phases of the alloyed layers were identified by an X-ray diffraction （XRD）. A Shimadzu Dynamic Ultra-micro Hardness System configured with a Berkovich （3--sided pyramid, 100°） diamond tip nano-indenter was used to measure the dynamic hardness and elastic modulus of both the substrate and the alloyed layer. The corrosion behaviors of the alloyed layer were evaluated by polarization experiments in 3.5% NaCl solution and 0.5% H2SO4 solution using a CHI 750 type electrochemical workstation. Three-electrode system was applied to determine the polarization curves. The measure- ments were conducted at 25℃ under atmospheric condition with a scanning rate of 0. 001 V/s. Some 304 L stainless steel specimens were also subjected to those experiments to give out a comparison. All the results indicate that a uni form, dense Ni--Cr alloyed layer had been synthesized without any cracks and holes on the surface of Q235 steel by the novel plasma surface alloying technique. And the average thickness of the alloyed layer is about 12μm. The sur- face grains self-assembled into larger particle groups. The prepared alloyed layer is composed of FeCr0. 29 Ni0. 16C0.06, Cre3C6 compound phases and y solid solution phase. The contents of nickel and chromium decrease gradually from the surface to the interior generally. However, the concentrations of both elements rise to a peak on the subsurface. The causing reason may be attributed to a reverse sputtering and reverse diffusion of the deposited atoms was taken place during the alloying process. The protective layer exhibits high dynamic hardness, high el
出处
《南京大学学报（自然科学版）》
CAS
CSCD
北大核心
2009年第2期223-229,共7页
Journal of Nanjing University（Natural Science）
基金
江苏省科技成果转化专项资金(BA2007036)
关键词
等离子表面冶金
镍
铬
耐蚀性能
surface alloying, nickel, chromium, corrosion resistance
