| Maritime powers are an important part of the national development strategy,and the harsh marine environment places stricter requirements on service equipment.Nickel aluminum bronze(NAB),as a common material for ship propellers,was prone to corrosion in marine environments with high salt and alternating cyclic loads.In recent years,the superhydrophobic surface has become a research hotspot in the field of material surface protection due to its special wetting interface relationship with corrosive media.Traditional methods for preparing superhydrophobic surfaces such as spray coating,electrochemical deposition,chemical etching,have limited applications due to the disadvantages of high consumption,and poor binding force.Picosecond laser is considered to be the most ideal method for preparing superhydrophobic metal surface due to its high precision,strong controllability,no pollution,short action time and high efficiency.In the paper,superhydrophobic NAB was successfully prepared using picosecond laser processing and various post treatment methods.The effects of different laser processing parameters on the surface morphology and wettability of NAB were studied.The superhydrophobic NAB was tested and analyzed.And the main conclusions are as following:(1)The wettability of a solid surface was determined by both the surface structures and the surface chemical compositions.The contact angle(CA)of the untreatment NAB surface was 80~o,but it showed superhydrophilicity after picosecond laser processing.In order to facilitate the investigation of the influence of laser processing parameters on the wettability transition of NAB surfaces,NAB was modified with fluorosilane after picosecond laser processing.The study found that when the scanning trajectory was parallel,the CA of the NAB surface decreased as the scanning intervals increased,and increased as the number of laser repetitions increased.In addition,only select the appropriate scanning speed to get the best surface wetting state.The best process parameters were obtained through experimental research.When the scanning interval was 20μm,the picosecond laser energy density was 2.01 J/cm~2,the scanning speed was 200 mm/s,and the number of repetitions was 10,the CA was 155~o and the sliding angle(SA)was 3~o.(2)When the scanning trajectory was crossing lines,the CAs of the NAB surface increased as the scanning intervals decreased.When the laser scanning intervals were less than 80μm,the surface wetting state of superhydrophobic NAB was Cassie-Baxter state,and when the scanning intervals increased from 80μm to 100μm,the surface wetting state transitions to Wenzel state.And the study found that the CA of the NAB surface increases with the number of repetitions.The best processing parameters obtained through experimental research are:when the scanning interval was 30μm,the picosecond laser energy density was 1.21 J/cm~2,the scanning speed was 200 mm/s,the number of repetitions was 10,and the maximum CA was 166~o,the SA was 2~o.(3)Superhydrophobic NAB was successfully prepared by different post-treatment methods,and the effect of different post-treatment process parameters on wettability transition was studied.The study found that when the samples was exposed to air after laser treatment,the CA increases spontaneously with time,and the smaller the surface microstructure size,the greater the maximum CA value,and the shorter the transition time.When the size was 30μm,the CA of NAB can reach up to 163~o after being exposed to air for 14 days.The low-temperature annealing method can shorten the spontaneous transition time.When the annealing temperature was 200 ~oC,the transition time was shortened to 14 h.In addition,the CA of the NAB surface modified with fluorosilane was 166~o,and the surface modified with stearic acid was 155~o.(4)Exploring the related properties of the prepared superhydrophobic NAB through various tests.Aging test showed that NAB prepared by different post-treatment methods can still maintain excellent superhydrophobicity after 60 days.The wear resistance test showed that the NAB modified with fluorosilane has more excellent wear resistance.The chemical stability test showed that NAB modified with stearic acid and fluorosilane was more stable,and the change of pH value of the test solution has little effect on CAs.Immersion corrosion and electrochemical tests show that fluorosilane modified NAB has better corrosion resistance.And research showed that the corrosion resistance of superhydrophobic NAB was mainly related to the size of the surface microstructure and the stability of the surface hydrophobic molecules.The smaller the size,the stronger the stability of the hydrophobic molecular layer and the better the corrosion resistance. |
