FeCrAlY-La2Zr2O7/La2Zr2O7-合金钢/合金钢基体高温耐磨隔热抗氧化梯度复合涂层激光增材制造技术

The core component of the inner diameter forming of seamless steel tubes is the piercing plug (mainly 15Cr2Ni3MoW (softening temperature is not higher than 1000 ℃) and other alloy steels). Under extreme conditions such as severe impact wear at high temperature (about 1150 ℃), the failure of the plugs caused by high temperature, pure oxidation-resistance and wear-resistance is a bottleneck problem restricting their life-times. At present, a layer of iron oxides with thickness of 150-450 μm is prefabricated on the top surface of the plugs by pre-oxidation. The maximum heat insulation is not more than 110 ℃. The structure is loose and easy to crack, and its oxidation-resistance and wear-resistance are poor. Therefore, the problem of rapid failure of the plugs can not be solved. In this project, a new idea of fabricating FeCrAlY-La2Zr2O7/La2Zr2O7-alloy steel/alloy steel substrate gradient composite coating with high temperature wear-resistance, heat insulation and oxidation-resistance (about 1 mm thick) by laser addition on the top surface is put forward. FeCrAlY will make the coating surface produce dense α-Al2O3 scale, which has high oxidation-resistance and wear-resistance. La2Zr2O7 has low thermal conductivity and good high temperature stability. La2Zr2O7 will be dispersed in the alloy coating to ensure that the coating has high thermal insulation (over 150 ℃), strength and hardness. This study could lay a theoretical and experimental foundation for the development of high efficiency, long life-time and high dimensional precision piercing plugs.

无缝钢管内径成形所依赖的最核心部件是穿孔顶头（以15Cr2Ni3MoW（软化温度不高于1000℃）等合金钢为主）。在高温（1150℃左右）剧烈冲击磨损等极端工况下，因高温、抗氧化和耐磨性差导致的顶头失效是制约其寿命的瓶颈难题。目前普遍采用预氧化在顶头表面预制一层厚150-450 μm的铁氧化皮，最高隔热不超过110℃，结构疏松易开裂，抗氧化和耐磨性差，无法解决顶头快速失效难题。本项目提出在顶头表面激光增材制造FeCrAlY-La2Zr2O7/La2Zr2O7-合金钢/合金钢基体高温耐磨隔热抗氧化梯度复合涂层（厚约1 mm）新思路。FeCrAlY使涂层表面产生致密α-Al2O3膜，起抗氧化和耐磨作用；La2Zr2O7具有低热导率和良好高温稳定性，弥散分布在合金涂层中，保证涂层具有高的隔热（超过150℃）、强度和硬度。本研究可为发展高效长寿命高尺寸精度穿孔顶头奠定理论和实验基础。

本项目针对无缝钢管穿孔顶头提前失效行业难题，提出了具有优异的抗高温氧化、耐磨、隔热性能的激光增材制造FeCrAlY-LZO（LZO为La2Zr2O7简称）复合涂层技术，本项目建立了复合涂层计算模型并对其隔热性能影响规律进行了模拟计算，研究了SLM工艺参数对MCrAlY涂层组织结构影响规律，揭示了制备工艺和成分对FeCrAl-LZO复合涂层组织结构的影响规律，系统阐明了复合涂层高温氧化行为及其影响机制，讨论了复合涂层高温摩擦磨损行为及其影响规律。获得以下主要研究结果：.（1）模拟计算结果表明复合涂层中强化相（LZO）占比和孔隙率对其热导率有重要影响，为了提高复合涂层隔热效果，应适当提高强化相占比和孔隙率。随着分散相在单元体内所占份额ω的增加，所需涂层厚度逐渐降低，ω每增加5%，所需厚度大致降低2.3 mm。.（2）SLM工艺参数（如激光功率/熔覆温度、扫描速率、扫描间距等）和粉末组成（如LZO含量、粒径大小、Al含量、Y2O3含量等）对复合涂层组织均匀性、致密度和显微硬度及热导率有重要影响。.（3）复合涂层中适当的含Al量可有效延长涂层表面氧化膜保持时间；由于MA影响，较低含Al量（4 wt.%、8 wt.%）复合涂层表面氧化物为α-Al2O3，含Al量（10 wt.%、12 wt.%）较高复合涂层氧化50 h时表面呈现θ-Al2O3形貌；低Al含量复合涂层氧化动力学曲线符合抛物线规律，较高Al含量复合涂层氧化过程中氧化膜出现了剥落；随着复合涂层中Y2O3含量增加，氧化膜增厚速率逐渐增大，但适量Y2O3可有效提高热循环次数，未添加Y2O3复合涂层循环80次后氧化膜开始剥落，而添加Y2O3复合涂层循环200次后均未发生明显失重。.（4）随着SLM激光功率/熔覆温度和LZO含量的提高，复合涂层摩擦系数和磨损量呈现先降低后升高的趋势；随着Al含量升高，复合涂层的摩擦系数和磨损率呈现先降低后升高再降低的趋势。. 本项目研究结果可为发展高性能无缝钢管穿孔顶头防护涂层奠定一定基础。

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