【作者】 王海涛；

【导师】 于化顺；

【作者基本信息】 山东大学 ， 材料加工工程， 2010， 博士

【摘要】 铁基高温合金是广泛应用于航空、航天、能源、冶金和石油化工等领域的高温结构材料。现代工业的高速发展对设备材料的高温抗氧化性能提出了越来越高的要求,通过复合氧化膜的高温抗氧化性能研究,对深入认识铁基高温合金抗氧化机理,寻求合金抗氧化的新工艺、新方法,提高合金抗氧化使用温度,进一步开发研制新型高性能铁基高温合金具有重要意义。本文以铁基高温合金K273与耐热钢ZG40Cr24为母合金,通过Al、Si元素合金化植入的方法,采用中频感应电炉不氧化法熔炼铸造试验合金。按照国标依据氧化增重的方法对试验合金进行1100℃,500小时抗氧化试验。通过SEM扫描电镜,EDS能谱分析,X-射线衍射分析,直流双桥电阻仪,激光导热仪等多种测试技术,系统研究了氧化膜形貌、氧化膜成分对试验合金抗氧化性能的影响；复合氧化膜的热力学生成；复合氧化膜生成后阻滞基体金属进一步氧化的机制；试验合金氧化动力学规律以及氧化膜高温热稳定性、抗剥落性。最后以实验为依据,结合理论分析研制了双相铁基高温合金,对其高温抗氧化性以及高温、室温强塑性进行了综合测试。高温合金K273与耐热钢ZG40Cr24通过合金化植入2wt.%Si+4wt.%Al后,高温抗氧化性能均得到显著提高,1100℃氧化增重速率分别由原来的12.2557g.m-2.h-1、3.53 1 9 g.m-2.h-1降低到0.3542g.m-2.h-1、0.0633g.m-2.h-1,由原来的不抗氧化、弱抗氧化提升为强抗氧化和完全抗氧化水平。通过金属元素氧化热力学计算建立了复合氧化膜的生成模型。试验合金于1100℃高温下,依据氧化物吉布斯生成自由能的大小,Fe、Cr、Ni、Mn、Al、Si等金属元素不断竞争氧化与还原,最终生成了由Cr2O3,α-Al2O3,SiO2及尖晶石Fe(Ni,Mn)Cr2O4组成的复合氧化膜。该复合氧化膜结构平坦,组织致密,氧化物颗粒度均匀细小,具有优异的抗氧化性能。通过氧化膜形貌,物相成份,元素分布等实验表征,以及氧化膜电导性与热扩散性的测量分析,研究了复合氧化膜的抗氧化机制。复合氧化膜是由P型半导体氧化物和N型半导体氧化物高度复合而成,减少了氧化膜内部离子、电子的扩散迁移数量,大大降低了金属基体的进一步氧化反应速度；同时,氧化膜内部的P、N型半导体氧化物组成了无数个PN结,PN结具有单向电荷导通性,无数个PN结在空间上呈现无序排列,各向同性,于是复合氧化膜任意方向均为电荷非导通状态,整体表现出电绝缘性质,因此复合氧化膜阻止了电化学腐蚀的进行,合金的抗氧化耐腐蚀能力极大提高。Al、Si元素的加入使高温合金K273与耐热钢的氧化膜抗剥落性大大增强,1100℃ZG40Cr24试验合金氧化膜剥落速率由原来的1.2681 g.m-2.h-1降低为0,达到完全抗剥落性。这是由于a-Al2O3与Fe基体体积比值：1.5<PBRα-Al2O3／Fe<2,以及N型半导体氧化物Si 0z于氧化膜外层生长,使生成的复合氧化膜既致密完整,又不产生生长应力破坏氧化膜。同时晶粒均匀细小的复合氧化膜通过Hall-Petch细晶强化原理大大增强了其自身的结合强度,因此复合氧化膜的高温热稳定性大大增强。通过对氧化增重数据的最小二乘法回归分析,复合氧化膜1100℃氧化动力学曲线严格遵循幂函数规律,幂函数方程为y=axb,(a>0,0<b<1),参数a、b共同影响曲线的位置高低和初始抗氧化能力,参数b决定了曲线趋于平稳的能力。b值的大小反映了合金抗氧化性能,b值增大,合金抗氧化性较差；b值减小,合金抗氧化性增强。通过合金化元素配比,研制了一种新型双相铁基高温合金：15Cr23Ni9Al3Si2,试验合金基体由奥氏体与铁素体两相组成。1100℃高温下,试验合金表层自发生成P+N型半导体复合氧化膜,氧化增重速率为0.0576g.m-2.h-1,氧化膜剥落速率为0,达到了完全抗氧化水平。试验合金室温拉伸强度达到σb 386.7MPa,屈服强度σp0.2305.8MPa,断面收缩率ψ5.8%；1100℃高温拉伸强度达到σb 122.5MPa,屈服强度σp0.295.5MPa,断面收缩率ψ18.4%。室温及高温强塑性达到较高水平。更多还原

【Abstract】 Ferro based supperalloys have broad prospect in the application fields of aircraft, spacecraft, energy resource, metallurgical and petrochemistry industrys. The zooming morden industry calls for critical high temperature oxidation ressitance of materials. By research of composite oxide scale on high temperature oxidation resistane, it is of great significance to understand the oxidation resistance mechanism, find new method and technology for oxidation resistance in higher temperature, and develop new unique properties ferro based supperalloys.Based on Ferro based supperalloy K273 and heat resistant steel ZG40Cr24, test alloys were cast by intermediate frequency induction furnace with non-oxidation method by alloying of Al and Si. The oxidation reistance at 1100℃for 500 hours of test alloys was carried out according to oxidation weight gain method by Chinese standard. By Scan Electricle Microscope, Energy Dispersive Spectroscope, X-ray Diffractor, Direct Current Resistance Meter, and Laser Thermal Conductivity, the effects of scale morphology and compositions on oxidation resistance were analyzed, the thermodynamic forming, oxidation resistance mechanism, oxidation kinetics, thermal stability and exfoliaton resistance of composite scale were studied systematically. A kind of dual phase ferro based supperalloy was developed on the experiment and theory analysis, and the high temperature oxidation resistance, high temperature and room temperature mechanical properties were examined.By alloy planting of 2wt.%Si and 4wt.%Al, the oxidation resistance of supperalloy K273 and heat rsistant steel ZG40Cr24 at 1100℃were both elevated remarkablely, the oxidation weight gain rate decreased from 12.2557g.m-2.h-1 and 3.5319g.m-2.h-1 to 0.3542g.m-2.h-1 and 0.0633g.m-2.h-1 respectively, the properties changed from none oxidation resistance to strong oxidation resistance for K273, and from the poor to the complete for ZG40Cr24.The growing modle of composite scale was established, by thermodynamics calculation of alloying elements. According to the Gibbs energy, Fe, Cr, Ni, Mn, Al, Si compete to be oxidated or deoxidated, so the composite scale made up of Cr2O3,α-Al2O3, SiO2 and spinel Fe(Ni,Mn)Cr2O4 came into being. Plane and compact structure, fine and even oxide grains endowed the composte scale with excellent high temperature oxidation resistance.By tests and analysis of oxides morphology, phase composition, elements distribution, electrical resistance, and thermal diffusion, the essence of composite scale oxidation resistance was fond to be that, the P type and N type semiconductor oxides in composite scale compose to be PN junctions, every PN junction is unilateral electrical conductivity, and numerous PN junctions arrange out of order in space, so the composite scale comes to be isolated on the whole, the transferring of ions and electrons in scale are hold back greatly, thus the further oxidation rate of base metal falls greatly, and the oxidation resistance of composite scale goes up markedly.With the adding of Al and Si, the scale exfoliation resistance of K273 and ZG40Cr24 was reinforced greatly, the scale exfoliation weight gain rate at at 1100℃descend from 1.2681g.m-2.h-1 to zero, reaching complete exfoliation reistance for ZG40Cr24 test alloy. Beacause of 1.5< PBRα-AlO3 Fe<2 and the growning of SiO2 from the out side of scale- scale/oxyzen interface, the composite scale grows whole and compact without accumulation of growing stress. At the same time, the even and fine oxides grains strengthen the scale intension by Hall-Petch theory. So the composite scale thermal stability of the boost up.According to the oxidation weight gains, the oxidation kinetics curves were plotted, and the equations were regressed by least squear method and none-linear curve fitting. The oxidation kinetics curves of composite scale strictly follow the power function of y=axb (a>0,0<b<1). The parametersαand b together affect the curve location and oxidation resistance, b determines the stability of curves and reflects the oxidation resistance of test alloys, the smaller, the stronger.By alloying of metal elements, a new type of dual phase ferro based supperalloy:15Cr23Ni9A13Si2 is developed. The base structure is made up of austenite and ferrite. At 1100℃, the P+N type semiconductor oxide scale comes into being spontaneously. With the oxidation wight gain rate of 0.0576 g.m-2h-1, and zero scale exfoliation, test alloy possesses complete oxidation resistance. With high temperature intension and plasticity:σb 386.7MPa,σp0.2 305.8MPa, (?)5.8%, and room temperature intension and plasticity:σb 122.5MPa,σp0.2 95.5MPa,(?)18.4%, test alloy reaches high level in mechanical properties.更多还原