【作者】 李二兴；

【导师】 刘胜新；

【作者基本信息】 郑州大学 ， 材料加工工程， 2012， 硕士

【摘要】 活塞杆是液压设备中的易损件,在使用过程中易出现磨损、腐蚀、变形等现象导致液压系统失效,延误生产进度。因此在活塞杆表面制备有防护层,目前国内主要采用电镀硬铬及复合镀铬、堆焊工艺制备和修复活塞杆表面防护层。火焰喷涂加感应重熔技术及等离子熔覆技术两种工艺均可在活塞杆表面制备高硬度抗磨耐蚀防护层的能力,且在成本、环境保护、适用性、规模应用等方面具有较强优势,但是有关这两种工艺在制备及修复液压支架立柱活塞杆方面的研究及分析不多。本文首先使用商业雾化粉末Fe90分别优化得到了火焰喷涂加感应重熔技术、等离子熔覆技术的最佳工艺参数,并在上述条件下,从成形性、防护层组织、结合强度、孔隙率、对合金粉末的要求及耐磨性能等方面分别对两种工艺的优劣进行了对比分析。另外,还结合液压支架立柱活塞杆的实际工作状况,设计并制备了耐磨耐蚀、抗形变的Fe基合金粉末防护层,并使用硬度计、金相显微镜、SEM、EDAX及XRD等检测手段分析所得防护层的力学性能和显微组织。在火焰喷涂加感应重熔技术中,当氧-乙炔流量比例为1.0、送粉量为97.7g/min、预热时间为40s、喷涂时间为3min、工件表面线速度为12.7m/min、重熔电源功率为60kW、频率为20kHz、感应线圈移动速率为4mm/min、试样表面温度为1100-1170℃时,能得到涂层沉积速率最大、粉末散失率最小、涂层与基材结合强度较佳的Fe90合金防护层。该防护层成形良好,与基材呈微冶金结合；硬度达到50～55HRC,内部组织致密,由HV849.5的奥氏体和HV948.4的针状共晶组成,层内存在少量孔隙；而使用最佳工艺参数得到的机械混合粉末Fe基合金防护层,则孔隙率高,力学性能较差。在等离子熔覆技术中,经实验得到的最佳工艺参数：喷嘴到基材距离为12mm、搭接率(搭接宽度)25%、熔覆电流为300A、熔覆速率为312mm/min、送粉量为50-55g/min。在上述参数得到的等离子熔覆Fe90合金防护层,成形良好,组织致密,且与基材呈完全冶金结合。熔覆层由大量枝晶组成；搭接区存在二次热致重结晶现象；热影响组织由片状珠光体、魏氏体区和再结晶区组成。结合液压支架立柱活塞杆表面防护层性能要求,通过正交实验得到适用于等离子熔覆技术的铁基合金粉末最佳配方：C4.5Cr23Ni6BSi4.5MnRE。经熔覆后的防护层,其组织主要由(Fe,Cr)7C3、(Fe,Cr)23C6硬质相和(Fe,Cr)-Y固溶体基体组成。磨损实验和腐蚀实验发现,该配方防护层耐磨耐蚀性能均优于Fe90等离子熔覆合金层。更多还原

【Abstract】 The poston of hydraulic pressure system was vulnerable point, and especially, it would be abrasion, rusty and out of shape, as a result, it delayed production and caused losses. So the coating over poston was made before used, the coating over poston were made and repaired widely used the processes of hard chromium or chromium composite electroplating and overlay welding in the past dacades. The flame spraying and plasma jet cladding process were suitable to produce and repair the hard, wear resistance, corrosion coating over hydraulic pressure poston, which take a lot of advantages such as low cost, environment protecting, applicability and widely used compared with electroplate, However, the research work on them is still insufficient.In this paper, Fe90alloy power, which was made by atomization method, was used to determinate the best technical parameters of the flame spraying plus induction remelting and the plasma jet cladding process. Under the best parameters, Comparision of the two processes was done in this paper from shape, structure, bonding strength, poison rate and conditions of powder. And then, according to working condition of hydraulic pressure supporting poston and the parameters, we design suitable Fe-based alloy power, detected and analysised the properties and structure of the coating by hardness tester, OM, SEM, ED AX, XRD and etc.The results presented that, in the process of flame spraying, when O2and C2H2flux ratio is1.0, transport powder rate is97.7g/min, preheat time is40s, spray time is3min, surface line speed of sample is12.7m/s, power of electricity-supply is60kW、frequency is20kHz, the temperature of the sample surface is about1100～1170℃, The flame spraying process is apply to atomization alloy powder, for example, Fe90alloy powder can be made into coating, whose hardness reaches50-55HRC, and its structure is compact, without pores. But the mechanically mixed powder it’s not suit to this process and the corresponding coating contains a lot of porosity. The optimizing parameters of the plasma cladding process are as follows:the distance between nozzle and ions is12mm, overlapping ratio (overlapping width) is25%, the welding current is300A, the welding rate is312mm/min, and the powder feeding rate is50-55g/min. Under parameters above, the well shaped and compact structure Fe90alloy plasma cladding overlay is obtained. The coating zone was consist of a large number of dendritic crystals. The heat affected zone mainly contains of ferrite, pearlite and widmanstatten. Recrystallization district was thermally induced in the overlapping zone.According to the requirement of overlay properties of poston, Fe-based powder C4.5Cr23Ni6BSi4.5MnlRE was the most optimization powder during orthogonal experiments. The cladding coating was consist of hard phase of (Fe,Cr)7C3and(Fe, Cr)23C6and alloyed y-solution matrix. The wear and corrosion resistence properties of this Fe-based alloy powder coating were better than Fe90plasma cladding overlay.更多还原