发动机排气门新型抗高温氧化涂层研究

目的提高排气门材料21-4N合金的抗高温氧化腐蚀性能和抗开裂剥落性能,提高排气门的服役性能,延长使用寿命。方法利用两步循环喷雾热解技术在21-4N合金表面制备(Al_2O_3-Y_2O_3)/YSZ层状陶瓷复合涂层,通过扫描电镜和能谱对涂层形貌和成分进行分析,通过循环氧化腐蚀实验评价涂层的抗高温氧化腐蚀性能和抗开裂剥落性能,通过划痕测试来评价涂层的结合强度。结果该层状复合涂层厚度均一、结构致密清晰,在900℃高温循环氧化100 h的实验中,该涂层样品的质量增加量和剥落量分别为0.3025和0.06 mg/cm~2,远低于无涂层21-4N合金的质量增加量和剥落量,具有优异的耐高温氧化腐蚀性能。该复合涂层的膜基结合力达到40 N,远高于21-4N合金表面氧化膜的结合力,能够满足排气门实际应用工况要求。结论采用两步循环喷雾热解技术在21-4N合金表面制备的(Al_2O_3-Y_2O_3)/YSZ层状复合涂层,能够有效提高排气门材料的抗高温氧化腐蚀性能,并具有优异的结合力。

Novel Coating of High-temperature Oxidation Resistance of Engine Exhaust Valve

The work aims to improve high-temperature oxidation resistance and anti-cracking spalling resistance of exhaust valve material like 21-4N alloy, enhance service performance and extend service life of engine exhaust valve. (Al2O3-Y2O3)/ YSZ laminated ceramic composite coatings were fabricated on the surface of 21-4N alloy by means of two-step cyclic spray pyrolysis technique. The morphology and composition were studied by virtue of SEM and EDS. The cyclic oxidation resistance tests were conducted to evaluate high-temperature oxidation resistance and anti-cracking spalling resistance of the coatings, while bonding strength was studied by performing scratching test. The laminated composite coating exhibited uniform thickness and compact microstructure. In the cyclic oxidation test conducted at 900℃ for 100 h, the sample with coating exhibited supe-rior high-temperature oxidation resistance, by which the weight gain and spalled mass were separately 0.3025 and 0.06 mg/cm2, far lower than that of 21-4N alloy without coating. The film-substrate bonding force (40 N) was apparently higher than that of 21-4N alloy, meeting the requirements of exhaust valve in actual working conditions. The (Al2O3-Y2O3)/YSZ laminated ceramic composite coatings fabricated on the surface of 21-4N alloy by means of two-step cyclic spray pyrolysis technique can improve high-temperature oxidation corrosion resistance of engine exhaust valve material significantly and contribute to excellent adhesion.