采用B4C和FeSi2对C/SiC刹车材料改性的新方法及其摩擦磨损机理

Serious abrasion and friction coefficient instability of the disk/pad brake pairs were produced when the full C/SiC (carbon-ceramic) brake disk and pad were used, which affect carbon-ceramic brake materials applied to the disk/pad brake systems, such as the high-speed train and automobile brake systems. The main reason is that the poor matrix toughness of the carbon-ceramic brake materials will lead to the brittle flaking off of the disk/pad friction interface during braking, and the friction interface is easy to produce oxidation wear to aggravate the brittle flaking off. The project intends to introduce the toughness matrix FeSi2 and self-healing component B4C into the brake materials by B4C slurry infiltration combined with FeSi75 melt infiltration process that reduce the oxidation wear and brittle flaking off to improve the friction and wear properties of the materials. The infiltration and reaction mechanism of FeSi75 melt and the microstructure formation mechanism of the friction components, the influence of the composition and microstructure on the properties of the B4C and FeSi2 modified carbon-ceramic brake materials, and friction and wear mechanism of the brake materials will be researched and revealed. And the matching design among the composition, microstructure and properties of the B4C and FeSi2 modified carbon ceramic brake materials will be studied. The project will improve the material system and process system of carbon-ceramic brake materials, and enrich the tribological mechanism of carbon-ceramic brake materials. The results will promote the applications of carbon-ceramic brake materials.

盘/片刹车副在使用全C/SiC（碳陶）刹车材料时磨损大，摩擦系数不稳定，影响其在高速列车和汽车等盘/片刹车结构中应用推广。主要原因是碳陶刹车材料基体韧性差，盘/片摩擦界面在刹车过程中易产生脆性剥落，而且摩擦界面易产生氧化磨损加剧脆性剥落。本项目拟通过B4C浆料浸渗结合FeSi75熔融浸渗工艺（RMI-FeSi75）在碳陶刹车材料中引入韧性基体组元FeSi2和自愈合防氧化组元B4C，降低摩擦界面的氧化磨损和脆性剥落来改善材料的摩擦磨损性能。研究并揭示FeSi75熔渗反应机理及材料的摩擦组元微结构形成机理，B4C、FeSi2改性碳陶刹车材料的组成/结构对材料性能的影响规律，以及B4C、FeSi2改性碳陶刹车材料的摩擦磨损机理；并研究B4C、FeSi2改性碳陶刹车副材料的组成/结构/性能匹配设计。本项目将完善碳陶刹车材料的材料体系及工艺体系，丰富碳陶刹车材料的摩擦磨损机理，为其推广应用奠定基础。

为解决传统三维针刺C/C-SiC刹车材料应用于盘/片刹车系统时存在磨损大、摩擦系数不稳定的问题，本项目提出向C/C-SiC中引入FeSi2合金组元，提高基体韧性来提升材料的抗磨损性能；向C/C-SiC中引入B4C，提升材料的抗氧化磨损能力。本项目系统研究了FeSi2/B4C改性C/C-SiC刹车材料的组成/微结构特征、力学性能、抗氧化性能、热物理性能和不同条件下的摩擦磨损性能。结果表明：.(1) 向C/C-SiC中引入FeSi2合金组元，改善了基体的韧性，在摩擦过程中抑制了基体脆性剥落，降低了磨粒磨损，显著提升了材料的抗磨损能力，将磨损率，尤其是高能载刹车时的磨损率降低了一个数量级以上，由1.4 μm/cycle降低至0.11 μm/cycle。.(2)在材料中引入适量FeSi2相（小于5 wt.%），材料的力学性能得以显著提升，抗弯强度由190±10 MPa提升至340±19 MPa。.(3) 采用浆料浸渍技术向C/C-SiC纤维束间引入B4C，显著提升材料的抗氧化能力，在空气中700℃ⅹ12 h氧化失重率由改性前的60%降低至17%，能显著降低材料的氧化磨损。.(4) 在C/C-SiC中引入B4C，材料在1000℃的比热容由3.52 J/cm3·K提升至4.12J/cm3·K，在高能载状态刹车时摩擦界面温度可降低100℃以上，B4C在摩擦过程中氧化生成B2O3，保护碳纤维和热解碳免于氧化，显著提升了材料的抗氧化磨损，使材料的线磨损率降低了50%以上。.通过对材料组成/结构与性能的研究，掌握了FeSi2/B4C改性C/C-SiC刹车材料的微结构形成机理，明晰了FeSi2合金相对材料力学性能的影响规律、B4C填料对材料的氧化防护机制，揭示了材料在不同条件下的摩擦磨损机理，为C/C-SiC刹车材料在高铁和汽车中的应用推广奠定了基础。