Manufacture And Study On Microstructure And Propertities Of Surface Pretected Coating Of Hydraulic Pressure Supporting Poston

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.