Investigation Of Corrosion Resistance For Surface Coating Of Superalloy Liner

As the requirement for the barrel corrosion resistance are higher and high with the gun development and progress,this study will improve the corrosion resistance of the gun barrel by employing the Ni-base single crystal superalloy with outstanding high-temperature mechanical properties as gun liner and fabricating NiCrAlY coatings on superalloy surface by means of two technologies,arc ion plating?AIP?and electrospark deposition?ESD?.In addition,aiming at the interdiffusion problem,the substrate pre-oxidation method was applied to prepared an active diffusion barrier?ADB?between AIP NiCrAlY coating and superalloy substrate to inhibit the elements interdiffusion.The nanoindentor,high speed reciprocating friction wear tester and high-temperature muffle furnace were used to test the properties of the hardness,elasticity modulus,fiction and wear,and high-temperature oxidation resistance of the samples,and the SEM?scanning electron microscope?,TEM?Transmission Electron Microscope?,EDS?Energy Disperse Spectroscopy?,EPMA?Electro-Probe Microanalyzer?and XRD?X-Ray Diffraction?were employed to analyze the morphologies,compositions and phase structures of the samples.The two coatings have different microstructure,of which the AIP coating is composed of?-Cr,?-NiAl and?-Ni whilst the ESD coating consists of?-NiAl and?-Ni.The hardness of the AIP and ESD coatings increased 14%and 19%and the elasticity modulus did 4%and 21%than those of the DD6 superalloy substrate,respectively.Moreover,the mechanism of the DD6 superalloy is characterized as severe abrasive wear while those of the AIP and ESD coatings belong to adhere and micro-cutting abrasive wear respectively.the fiction coefficient of the AIP?0.42⁰.47?and ESD?0.27⁰.32?coatings reduced that of the substrate?0.50⁰.57?and have obvious antifriciton effect.After oxidizing at 1100?for 100 hours in air,the DD6 superalloy surface formed three layers of oxides,Ni?Co?O,spinels and?-Al₂O₃ from top to bottom,and differently,the two coating surface both formed continuous and compact oxide scale,of which the AIP coating mainly consists of?-Al₂O₃ whilst the ESD coating is mainly composed of?-Al2O3 and?-Al2O3.Therefore,the two coatings both significantly improve the high-temperature oxidation resistance of the superalloy substrateA Ni?Co?O ADB was fabricated by superalloy substrate pre-oxidation method at the AIP NiCrAlY coating/DD6 superalloy substrate interface and it transformed a quasi-sandwich structure by in situ reaction at 1100?,which not only has good adhesion with the coating and substrate,but also possess excellent barrier ability.The experimental results at 1100?f or 220 hours in air showed that the pre-oxidation ADB improves the high-temperature oxidation resistance of the AIP NiCrAlY coating/DD6Ni-base single crystal superalloy system...