Mechanism Of Femtosecond Laser Adjusting Si₃N₄ Ceramic Wetting Gradient Surface

In this article,the surface of ceramic tool materials is treated by a femtosecond laser.The effect of laser multi-parameters on the surface wettability of ceramic tools was revealed.The mechanism of laser wettability on the surface of ceramic tools was revealed,and a gradient wettability surface was constructed.In view of the rapid wear and high surface temperature of Si₃N₄ ceramic tools during cutting,the femtosecond laser is used to treat the micro-nano structure on the surface of Si₃N₄ ceramic samples,thereby changing the surface morphology and wettability,and on the basis of this,the wettability is improved.The inclined surface can promote the flow of cutting fluid,thereby improving the cutting performance of the tool.The specific research content and conclusions are as follows:?1?Micro-pit array structures were prepared on the surface of Si₃N₄ ceramics using femtosecond laser.The effects of different laser average power,scanning time and micro-pit distribution density on surface morphology and contact angle were studied.By changing the distribution density of micropits,wetting surfaces with different gradients were constructed,and the relationship between the distribution density gradient and the wetting time and wetting distance was established.The experimental results show that the diameter and depth of circular micropits increase with the change of laser power and scanning time.However,because the micropit geometry produced by the two methods is different,the contact angle will gradually decrease as the number of scans increases.As the average power increases,the contact angle will gradually decrease and then increase.As the density of micropits increases,the solid-liquid contact area increases exponentially,and the contact angle tends to decrease and gradually stabilize.On a gradient-permeable surface,the droplets first diffuse rapidly under the influence of the potential energy of gravity.As the droplets spread further,the non-equilibrium surface tension caused by the difference in contact angle becomes the main influencing factor.The differences in wetting distances between the three gradient infiltrating cutting fluids on the surface gradually increased.The larger the density gradient of the micropores,the more favorable the directional diffusion of the cutting fluid.?2?Using a femtosecond laser to process a continuous arrangement of gradually changing roughness on the surface of Si₃N₄ ceramics,use an optical profiler and a contact angle meter to measure the surface roughness and contact angle,respectively,to study the average laser power,the number of scans and the speckle overlap.Influence of surface roughness and contact angle.By changing the number of laser scans,wetting surfaces with different gradients are constructed,and the relationship between the roughness distribution gradient,wetting time,and wetting speed is established.The experimental results show that with the increase of the average laser power and the number of scans,the surface roughness of the sample increases to varying degrees,the surface contact angle increases first,then decreases,and the trend becomes slower.The increase of dot overlap can effectively improve the surface roughness and reduce the contact angle.The rational design of the surface roughness distribution can obtain invasive surfaces with different gradients.Droplets are affected by unbalanced surface tension caused by differences in contact angles.The wet distance difference gradually increases.The larger the roughness distribution gradient,the better the fluidity of the cutting fluid,and the instantaneous average wetting speed generally shows a downward trend,accompanied by obvious fluctuations.