【作者】 周云龙；

【导师】 盛忠起；

【作者基本信息】 东北大学 ， 机械工程（专业学位）， 2019， 硕士

【摘要】 紧固件作为应用范围最广的工业三大基础零件之一,在社会生产中发挥着不可替代的作用。随着人类对海洋资源的逐步开发和各种海上基础设施的兴建,紧固件的需求量不断增加。又由于我国东南沿海及其附近岛礁地区常年处于高温、高湿、高盐雾、多霉菌、强日照、强风(“三高一多两强”)的自然环境下,紧固件腐蚀情况尤为突出,特别是海上交通不便,各种结构、设备的维修和维护工作难以进行。且紧固件腐蚀后只能够采用新的紧固件来替代,由此造成了极大的不便与浪费。机械能助热扩渗技术是近年来紧固件行业应用最为广泛的先进表面处理技术,可以制备出防腐、耐磨性能优异的渗层,并且生产过程绿色、无污染。本论文采用机械能助热扩渗技术,以锌、铝、镍粉为供渗剂,通过调整450℃低温环境下渗剂中Zn、Al、Ni元素所占的比例及机械能助渗工艺参数,在45#钢基体表面制备出防腐性能优越的合金渗层,以达到延长螺栓紧固件使用寿命的目的。论文的主要研究内容如下:(1)通过预试验和优化试验,对渗层的表面和截面形貌进行了观察和分析,对渗层的表面硬度、孔隙率及结合强度进行了测量和计算。确定了优化后的渗剂配方及助渗工艺参数为:供渗剂(15%Al-35%Zn),活化剂(0.02%NH4Cl),催渗剂(0.05%稀土)及填充剂(余量为Al2O3);保温温度450℃,保温时间4h,渗炉转速7r/min。(2)采用XRD(X射线衍射)及EDS(能谱仪)对渗层进行物相组成及成分分布分析。结果表明:优化后渗层物相主要为Al2O3、Г1相(Fe11Zn40)和δ1相(FeZn6.67、FeZn8.87、FeZn10.98)Zn-Fe合金;Al元素主要集中在渗层表面,靠近渗层表面处的Zn-Fe合金主要为FeZn10.98;靠近渗层与基体分界线处的Zn-Fe合金主要为FeZn6.67;基体与渗层间存在厚度约5μm的过渡区,过渡区中存在一层富碳层,并且Zn、Fe元素含量在过渡区发生陡变。(3)以不同渗剂配方和助渗工艺参数制备的渗层为研究对象,进行了摩擦磨损试验,通过磨痕三维形貌、宽度、深度、磨损体积及摩擦系数曲线对渗层进行耐磨性能表征。结果表明:制备的渗层耐磨性能均优于基体,渗剂中Al含量的提高有助于增强渗层表面的耐磨性能,并且助渗工艺参数的变化对渗层的耐磨性能无明显影响。(4)以不同渗剂配方制备的渗层为研究对象,对其进行电化学分析,并研究了助渗工艺参数优化后制备的渗层在3.5wt.%NaCl环境中的腐蚀机理。结果表明,腐蚀主要过程为:浸泡0-24h,低频区阻抗模值降低,容抗弧半径变小,此时腐蚀溶液侵入渗层,渗层快速腐蚀;浸泡72-360h,低频区阻抗模值和容抗弧半径逐渐增大,此时为腐蚀扩散阶段,渗层的腐蚀速率逐渐下降;浸泡360h后,渗层仍具备优异的防腐效果。(5)通过全浸试验和盐雾试验对渗层进行了耐蚀性能测试,并进行了腐蚀产物成分分析。结果表明:优化后的渗层经1000h浸泡后,腐蚀速率仅有0.88×104g.m-2.min-1,且腐蚀产物能够牢固地填充入渗层表面的孔隙中。盐雾腐蚀前期的腐蚀产物主要为ZnO及Zn5(OH)8Cl2H2O;盐雾腐蚀中期的腐蚀产物中出现了ZnAl2O4和不稳定的腐蚀中间产物FeOCl;盐雾腐蚀后期的腐蚀产物中ZnAl2O4相消失,多了 Zn(OH)2、Al(OH)3相。更多还原

【Abstract】 As one of three basic parts of the industry with widest application range,the fastener plays an irreplaceable role in social production.With the gradual development of marine resources and the construction of various marine infrastructure,the demand for fasteners is increasing.In addition,due to the high temperature,high humidity,high salt fog,much mold,strong sunlight and strong wind(three highs,one much and two strong),the corrosion of fasteners is particularly prominent in the southeast coast of China and the nearby islands and reefs all year round.Especially in the case of inconvenient sea transportation,it is difficult to carry out repair and maintenance work on various structures and equipments.Moreover,the fasteners can only be replaced by new fasteners,which causes great inconvenience and waste.Mechanical energy-assisted thermal infiltration technology is the most widely used advanced surface treatment technology in the fastener industry in recent years,which can produce an infiltrated layer with excellent corrosion resistance and wear resistance,in addition,of which the production process is green and pollution-free.In this thesis,the mechanical energy-assisted thermal infiltration technique is adopted,and zinc,aluminum and nickel powder are used as the infiltration agent.By adjusting the ratio of Zn,Al and Ni elements in the infiltration agent and the mechanical energy-assisted infiltration process parameters at low temperature environment of 450℃,an alloy infiltrated layer with superior corrosion resistance is prepared on the surface of 45#steel matrix to achieve the purpose of extending the service life of fastener bolts.The main research contents of the thesis are as follows:(1)The surface and cross section morphology of infiltrated layers were observed and analyzed through pre-test and optimization experiments.The surface hardness,porosity and bonding strength of infiltrated layers were measured and calculated.The optimized infiltration agent formulation and the infiltration process parameters were determined as follows:infiltration agent(15%Al,35%Zn),activator(0.02%NH4Cl),catalyzer(0.05%RE)and filler(the balance is Al2O3),the holding temperature is 450℃,the holding time is 4h,and the infiltration furnace speed is 7r/min.(2)XRD diffraction analysis and energy spectrum analysis were used to analyze the phase composition and composition distribution of infiltrated layers.The results show that the main phases of the optimized infiltrated layer are Al2O3,Γ1 phase(Fe11Zn40)and δ1 phases(FeZn6.67,FeZn8.87,FeZn10.98)of Zn-Fe alloys.The Al element is mainly concentrated on the surface of the infiltrated layer,the Zn-Fe alloy near the surface of the infiltrated layer is mainly FeZn10.98,and the Zn-Fe alloy near the interface between the infiltrated layer and the substrate is mainly FeZn6.67.There is a transition zone between the substrate and the infiltrated layer with a thickness of about 5 μm.A carbon-rich layer exists in the transition zone,and the content of Zn and Fe elements changes sharply in the transition zone.(3)Friction and wear tests were carried out on the infiltrated layers prepared with different formulations and process parameters.The wear resistance of the infiltrated layer was characterized by the three-dimensional morphology,width,depth,wear volume and friction coefficient curves of the wear marks.The results show that the wear resistance of the infiltrated layers is better than that of the substrate.The increase of Al content in the infiltrated layer helps to enhance the wear resistance of the surface of the infiltrated layer,and the change of process parameters has no significant effects on the wear resistance of the infiltrated layers.(4)The electrochemical analysis was carried out on the infiltrated layers prepared with different infiltration agent formulations.The corrosion mechanism of the optimized infiltrated layer in a 3.5wt.%NaCl environment was studied.The main corrosion process is found as follows:1)in the time zone of 0-24h,the impedance modulus of the low frequency region is reduced,and the radius of the capacitive anti-arc becomes smaller,the corrosion solution invades the infiltrated layer and the layer is quickly corroded;1)in the time zone of 72-360h,the corrosion is diffused clearly,and the impedance modulus of the low frequency region and the radius of the capacitive anti-arc gradually increases,and the corrosion rate of the infiltrated layer gradually decreases;3)after soaking for 360h,the infiltrated layer still has excellent antiseptic effect.(5)The corrosion resistance of the infiltrated layer was tested by the full immersion test and the salt spray test,and the composition of corrosion products was analyzed.The results show that after the optimized layer was soaked for 1000the corrosion rate is only 0.88×10-4g·m-2·min-1.And the corrosion products can be firmly filled into the pores on the surface of the infiltrated layer.The corrosion products in the early stage of salt spray corrosion are mainly ZnO and Zn5(OH)8Cl2H2O.The corrosion products in the middle stage of salt spray corrosion are ZnAl2O4 and the unstable corrosion intermediate FeOCl.The ZnAlO4 phase in the corrosion products in the later stage of salt spray corrosion disappears,but Zn(OH)2 and Al(OH)3 phase appear.更多还原