Research Of The Properties Difference Behavior Of Plasma Sprayed Nickel-based Coatings Based On The Size Effect Of Powder

In the process of exploiting Marine resources,more and more machines are scrapped due to seawater corrosion and mineral wear.How to avoid all kinds of marine equipment and its parts from corrosion and wear in seawater is a hot issue of human concern.The thermal spraying protective coating prepared by plasma spraying technology is one of the effective methods to solve this problem.Therefore,the NiCrBSi coating was prepared on 2Cr13martensitic stainless steels surface by plasma spraying technology,and the influence of powder size on the microstructure,properties and quality of the coatings.Firstly,the electrochemical corrosion behavior of NiCrBSi powder induced coating was studied.The distinction in the properties of both coating samples(50-75C and 75-100C prepared by 50-75?m and 75-100?m powder)mainly resulted from using different-sized powders.The same weight of powder would possess a larger total surface area due to the smaller size.Small in-flight particles were prone to be melted in the plasma arc,therefore the50-75C showed a larger volume fraction of the amorphous phase(15.5%)and a low hardness(700±41HV0.5)after the fast solidification on the surface of the substrate.After the influence of amorphous was eliminated by heat treatment,the hardness of small particles(850±111HV0.5)was reversed by large particles(800±82HV0.5).Meanwhile,owing to the limited diusion between deposited particles,smaller particles also resulted in a greater number of non-bonded boundaries in the as-sprayed 50-75C,thereby degrading its corrosion resistance.Therefore,as-sprayed 50-75C had a higher corrosion current density(0.254±0.062?A/cm~2)than the 75-100C(0.189±0.069?A/cm~2).Correspondingly,the charge transfer resistance of the as-sprayed 50-75C was also lower than that of the 75-100C.Thus,the corrosion resistance of 50-75C was lower.However,the improvement of its properties was limited due to the limitation of nickel-based alloy,so a new way was sought to improve the coating properties.It was found that the composite coating formed by mechanical mixing of NiCrBSi powder and ceramic powder could effectively improve the performance of the coating.Nano-yttrium stabilized zirconia(YSZ)powder is widely used due to its high hardness,high wear resistance and other properties.Therefore,the performance differences of the composite coating formed after adding different content of nano YSZ powder to NiCrBSi powder were investigated below.It was found that the aggregation of nano-YSZ particles in Z2 coating(2%YSZ+NiCrBSi)in the form of small droplets could enhance the hardness of the coating.Z6(6%YSZ+NiCrBSi)and Z10(10%YSZ+NiCrBSi)composite coatings could be found that nano-YSZ particles aggregated in the form of strip shape,which weakened the bonding between the coatings and reduced the average hardness of the composite coating.The hardness of Z6composite coating(825±96HV0.5)was lower than that of Z2 composite coating(910±70HV0.5).The wear mechanism of spray coating was abrasive wear,and the wear mechanism of Z6 and Z2 composite coating was adhesive wear.The presence of nano-YSZ would increase the bite between the composite coating and Fe transfer layer,and the increase of Fe transfer layer would also prevent the wear damage on the worn surface,delayed the loss of NiCrBSi and nano-YSZ particles,and ultimately reduced the wear mass loss and improve the wear resistance.There is a significant difference between the friction and wear behavior of composite coating and as-sprayed coating.The relationship between the coating corrosion resistance and the size effect of the powder was studied on the basis of some composite coating parameters in the friction and wear experiment.The melting degree of M coating(micro-YSZ+NiCrBSi)was better than that of N coating(nano-YSZ+NiCrBSi).The electrochemical comprehensive data showed that adding YSZ powder can improve the corrosion resistance of NiCrBSi coating,and the addition of YSZ powder could make the pores and gaps in the coating filled,which could effectively prevent the ions in the solution from passing through the coating.M coating had higher charge transfer resistance(0.445M?cm~2)and lower corrosion current density(0.175?A/cm~2),which was closely related to the dense layered structure of M coating.The results showed that the size effect of the powder had a significant impact on the performance of the coating.Adding YSZ powder could improve the corrosion resistance of the coating,but it was not that the smaller the size of the powder,the better the performance of the coating.In addition,the content of added powder had a good research value in improving the performance of the coating.