【作者】 王静；

【导师】 王佳； 李相波；

【作者基本信息】 中国海洋大学 ， 应用化学， 2008， 硕士

【摘要】 随着航空、航海技术的快速发展,对发动机、内燃机材料强度的要求不断提高,尤其是处于腐蚀环境中的部件,常规涂层和阴极保护技术无法满足其长效防护的要求,因此,耐腐蚀、耐高温及抗磨损的新型材料不断涌现,喷涂金属/陶瓷涂层是目前提高内燃机、发动机经济性和可靠性最有效的方法。金属/陶瓷复合涂层既有良好的隔热效果,又有耐磨、耐腐蚀及热冲击性能,在高温工作的材料中得到了广泛的应用。中间过渡层的引入缓解了因金属与陶瓷的热膨胀系数差异引起的热应力,使涂层的内聚强度和涂层与基体的结合强度都得到明显提高,从而改善涂层的抗热震性能,提高涂层的服役寿命。冷气动力喷涂是一种新兴的技术,该技术是一种基于空气动力学原理的材料表面改性新技术,它利用低温(〈600℃)预热高压气体携带粉末颗粒经缩放型拉瓦尔喷管形成超音速气-固双相流,以超高速在完全固态下撞击基体。在整个过程中由于喷涂温度低,粒子保持固体状态、不会发生化学反应及相变、不易发生固体粒子长大及氧化现象。在一定程度上弥补了热喷涂技术的缺陷,为改善复合涂层耐高温耐腐蚀性能开辟了新的道路。论文从金属/陶瓷涂层的隔热特性、热应力分析入手,用ansys有限元软件分析了不同材料组成、不同厚度、不同结构涂层的隔热特性和热应力分布,得出了涂层隔热特性及热应力与涂层材料、结构、厚度的关系,为复合涂层结构的选定提供指导。利用数值模拟软件Gambit、Fluent等,计算CoNiCrAlY和ZrO2颗粒在喷涂过程中由喷嘴入口至基板的撞击速度,研究不同的颗粒尺寸、气体、入口温度、压力和环境压力等工艺参数及喷嘴结构对颗粒撞击速度的影响,将冷喷涂工艺参数定为:喷涂气体选择氦气,喷涂温度:450～500℃,喷涂压力:1.5～3.0Mpa,喷涂距离:15～30mm,膨胀比:5～10。并用ANSYS/LS-DYNA软件模拟了CoNiCrAlY和ZrO2颗粒喷涂撞击过程,为冷喷涂制备金属/陶瓷复合涂层提供理论依据。本论文解决了复合涂层中合金粘结底层的制备工艺及其性能研究。用氦气作为主气制备了CoNiCrAlY合金涂层、ZrO2-CoNiCrAlY金属/陶瓷涂层、Al-CoNiCrAlY涂层。因氦气价格高而且用量大,使喷涂的成本较高,为了降低喷涂成本,尝试使用空气制备CoNiCrAlY合金,由数值分析可知:空气作为主气时,达不到CoNiCrAlY合金的临界速度,所以喷涂效果不是很好。在CoNiCrAlY合金里加入10%和5%的铝,用空气制备出了结构致密的Al-CoNiCrAlY合金涂层。运用扫描电镜(SEM)、能谱分析(EDS)对制备的涂层进行表观形貌分析,发现喷涂粒子之间是通过高速碰撞发生强烈塑性变形而结合在一起,涂层内部致密性很好,喷涂过程中未发生明显氧化;通过对涂层显微硬度的测试表明,由于冷喷涂过程中喷涂粒子的喷丸强化作用,冷喷涂合金涂层的显微硬度较高,尤其是添加了ZrO2的合金涂层,这说明涂层的局部抗压、耐磨性能较好;对涂层孔隙率的分析表明,冷喷涂合金涂层的孔隙率非常低,说明涂层较致密,不存在贯穿到基体的孔隙,可以有效防止腐蚀介质的渗透;结合强度试验表明,断裂都是发生在涂层与基体之间,冷喷涂合金涂层内部的结合强度比涂层与基体之间高。抗热震性试验表明,冷喷涂合金涂层的抗热震性性能很好,添加了ZrO2的合金涂层经过12次的热震试验后发生局部剥落;添加了Al的合金涂层经过12次热震试验后涂层依然没有剥落,说明冷喷涂制备的合金涂层抗热震性能很好。海水浸泡试验和中性盐雾试验表明,冷喷涂合金涂层结构致密,孔隙率低,可以较好的阻止腐蚀介质向涂层内部及基体渗透,延长了涂层的使用寿命,有效的保护了基体。因为本论文是在相关文献很少的基础上用冷喷涂技术制备的金属/陶瓷涂层,并进行了冷喷涂参数的优化及涂层性能分析。整个研究需要深入涉及的内容较多,应用到实际工业生产还有许多内容需要进一步地深入和完善。更多还原

【Abstract】 With the continuing development of aviation and navigation, the demand for the materials with higher performance for gas turbine and the internal combustion engine is increasing. Conventional coating and cathodic protection cann’t meet the protection demand especially for the components in the severest corrosion environment. So the materials with high-temperature resistant and corrosion-resistant have been developed continuously, and, at present, spraying mental/ ceramic coating is the most effective way to improve the economy and reliability of the gas turbine and the internal combustion engine.Mental/ceramic coatings have been widely used in the high temperature environment for its good thermal insulation, corrosion resistant and wear resistant properties. The interlayer is introduced into the mental/ceramic coating to decrease the high thermal stress caused by the mismatch of the thermal expansion coefficient, it is able to improve the combination, thermal-shock resistance and service life of coating.First, the ansys software was used to implement the theoretical calculation of temperature fields and thermal stress fields in the mental/ceramic coating. The influence of the material, structure and thickness on the thermal insulation and thermal stress of the coating was studied.Second, the accelerating behaviors of the CoNiCrAlY and ZrO2 particals were simulated through Gambit and Fluent software. The influence of different process parameters and nozzle structure on the accelerating behaviors was investigated, the appropriate spray parameters were obtained, gas temperature: 450～500℃, gas pressure: 1.5～3.0Mpa, spray distance: 15～30mm, expansion ratio:5～10. The impinging simulation in the spray process of the CoNiCrAlY and ZrO2 particals was also studied through the ansys software.Third, the coatings were prepared with the appropriate spray parameters, CoNiCrAlY , ZrO2-CoNiCrAlY and Al-CoNiCrAlY coatings are prepared with helium gas. Because the helium gas is very expensive, the CoNiCrAlY coating with air gas was studied for decreasing spray cost, though it was difficult at the beginning, and finally, the Al-CoNiCrAlY coating was prepared successfully with air gas.At last, the performances of the coatings were also studied. The apperarance of coating was observed through SEM and EDS. The results showed that the coating was deposited through intensive plastic deformation of the spray particles by high-speed impact, and no oxidation phenomena discovered in the cold spray process. The microhardness of the coating is high because of the shot peening strengthening in the cold spray. With optical microscopy, it is found that the coating has lower porosity, and can avoid crrosive medium penetrating into the coating. The combination test showed that the adhesion strength between coatings is higher than that between coating and substrate, and the coating combined physically to the substrate through the plastic deformation of spray particles.The thermal shock resistance test showed that the coating has high thermal shock resistance, particle spalling occurred for the ZrO2-CoNiCrAlY coating after 12 times thermal shock resistance test, the Al-CoNiCrAlY coatings endured 12 times thermal shock were perfect without any defects, such as crack and spalling. In order to study the corrosion resistance of the coating, the seawater corrosion resistance test and the neutral salt spray test were performed. The results indicated that the steel can be effectively protected by the cold-sprayed coating.In order to put this process into industrial use, there are still many problems waiting for further research and improvement.更多还原