| TiN has the characteristics of high hardness,high wear resistance,low friction coefficient of ordinary ceramics,and also has good corrosion resistance and chemical stability.In the previous study,nano TiN coatings were prepared by reactive plasma spraying,but it was found that micro-cracks perpendicular to the metal substrate influenced the performance of TiN itself.In order to improve the microstructure of the TiN coating and to improve wear and corrosion resistance of the coating,Ni/PEEK composite powders were prepared by spray drying,and TiN-Ni/PEEK composite coatings were prepared by reactive plasma spraying Ti and Ni/PEEK mixture powders.The effect of ball milling process on the composite powder was investigated.The microstructure of TiN-Ni/PEEK composite coating with different Ni/PEEK content were studied.The wear and corrosion failure mechanism of composite coatings were also analyzed.The results were as follows:?1?The ball milling process optimized the microstructure of Ni/PEEK composite powder.The ball milling process refined Ni powder and made the surface of powders be smooth.The Ni/PEEK powder prepared by ball milling Ni powder has good cover function.The best spray power is 24kW,composite coatings sprayed with the power of24kW have more compact structure.The composite coating possesses typical lamellar structure.Ni and PEEK is dispersed in the coating,and PEEK did not degrad.The composite coating is mainly composed of TiN,Ni,Ti3O and PEEK.?2?In the case of the same content of Ni/PEEK,TiN-Ni/PEEK composite coatings made of ball-milling Ni powders has higher micro-hardness than composite coating made of commercial Ni powders.The hardness of the coating decreases with the increase of Ni/PEEK content.The friction coefficient of two kinds of composite coatings decreased,and then increases with the rise of load.When the content of Ni/PEEK is 40 wt.%,the friction coefficient and the wear loss are the lowest.The wear mechanism of composite coating is fatigue brittleness fracture under the condition of low load,and it is mainly abrasive and fatigue wear under condition of high load.?3?Under the condition of 200?,the friction coefficient of composite coating is only 0.184,which shows that the coating exhibits better self-lubrication at 200?.?4?The corrosion resistance of the composite coating enhanced with the increase of Ni/PEEK content when it is in salt spray.The corrosion resistance time of the composite coating with 30%Ni/PEEK is about 5 times that of TiN coating.The corrosion time of composite coating with 40 wt.%is about 15 times that of TiN coating.?5?With the increase of Ni/PEEK content,the corrosion potential of the composite coating increased,the corrosion current decreased,the protective time of the composite coating is prolonged,and the corrosion resistance of the composite coating is enhanced.The equivalent circuit of TiN-Q50%composite coating changed from R?Q?R?QR???to R?Q?R?Q?RW????with the time prolonged. |
PDF Full Text Request