| A higher request has been put forward for the wear resistance and operating temperature of cannon gun tube with the continuous development and progress of modern artillery.In order to improve the performance and service life of the gun barrel,an MCrAl Y coating was deposited on the surface of PCrNi3 MoVA steel substrate by mean of electrospark deposition technology.The law of mass transfer was investigated by adding two kinds of electrodes?PCrNi3MoVA and W-Ni-Fe?.In the light of the actual working condition of the gun barrel,the friction and wear tests were carried out by utilizing nano indentation tester and high speed reciprocating friction and wear tester.The isothermal oxidation experiment of the samples at 900 for 100 hours was carried ?out by using discontinuous weighing isothermal oxidation method.The original microstructure,morphologies after wear and oxidation testing,and oxide composition of the samples were analyzed using SEM,EDS,XRD and other testing means,which could establish the theory basis for the application of MCrAlY coating on the gun barrel.For the NiCrAlY,PCrNi3 MoVA and W-Ni-Fe anode materials,the anodic corrosion quantity is inversely proportional to its melting point,and the NiCrAlY electrode has a lower melting point,so it has a highest corrosion quantity.The mass transfer coefficients of the three electrode materials show that the NiCrAlY electrode has a high efficiency,which can be applied for build-up welding and repairing.The electrospark deposited NiCrAlY coating,which has a is metallurgical bonding with the substrate,is continuous and dense.The coating with columnar superfine grain structure,which is composed of ?-NiAl and ?-Ni,is formed by the mixing the element Ni,Cr,Al from the anode and the element Fe from the substrate.The hardness of the NiCrAlY coating was increased by 22% compared with the substrate whilst the modulus of elasticity was lower than that of the substrate.In friction and wear test,the coating had lower friction coefficient on the same reciprocating speed,and with the increase of the friction velocity,the friction coefficient of the NiCrAlY coating decreased.The main wear mechanism of the substrate could be characterized as severe plastic flow and abrasive wear while the wear mechanism of NiCrAlY coating is micro-cutting abrasive wear.The severe oxidation took place for the PCr Ni3 MoVA steel at 900 for 100 hours,?however,and the NiCrAlY coating was a completely antioxidant level.The oxidation kinetics curves of the PCrNi3 MoVA steel and NiCrAlY coating approximately obeyed the parabolic law,nevertheless,and the weight gain of PCrNi3 MoVA steel was 135 times compared with that of the NiCrAlY coating.Oxide films composed of Fe2O3,Fe3O4 and FeO,a sparse layered structure,were formed on the surface of the PCrNi3 MoVA steel and they had the phenomenon of the cracking and spalling from the substrate A continuous,intact and compact oxide film mainly composed of Al2O3 was formed on the surface of the NiCrAlY coating,which improved the oxidation resistance of the PCrNi3 MoVA steel substrate. |
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