Study On Static Solution Assisted Laser Drilling

Laser drilling is an highly efficient and precise special processing method.Because of its high precision,high energy,high flexibility and high efficiency,it(is)widely used in drilling of Engineering materials.Alumina ceramic is a high temperature-resistant,corrosion-resistant,wear-resistant materials.In aero-engine and aviation high-temperature heat shield and other fields more widely used.But because of its characteristics of high strength and great brittleness,the traditional mechanical processing method has been difficult to meet the needs of today.The laser has a distinct advantage in the processing of ceramic materials,however,there are some defects such as large taper,low roundness,large amount of slag accumulation,ablation,recast layer and micro-cracks when the laser drilling the alumina ceramic,thus affecting the drilling quality,directly affects the life of parts.In order to solve the above problems in the process of laser drilling,the self-made clamping device is used to assist laser drilling with static solution to improve the processing quality and reduce the micro-defects.At the same time,it also has the advantages of environmental protection and low cost.In this paper,Nd:YAG pulsed laser was used to spot-seal the alumina ceramic sheets with a thickness of 1mm.The alumina ceramic sheets were placed in air holes,aqueous solution(primary drilling and secondary drilling),sodium chloride salt solution(Once perforation and second perforation)for experimental study.Through single-factor experiments in five kinds of drilling methods(laser air drilling,a laser drilling in water,laser drilling in water twice,the laser drilling in a salt solution,the laser twice in salt solution Hole)to study the quality characteristics of alumina ceramic punching,by measuring the aperture and calculating the taper and roundness of the hole,the laser parameters as well as the influence of the static solution on the punched hole quality are analyzed.The slag and erosion in the drilling process were analyzed by metallographic microscope and scanning electron microscope.Recast layers and microcracks are analyzed.The formation,solidification and solution change of the laser drilling under various environments are investigated by means of a high-speed camera.And the distribution of temperature field during laser drilling is analyzed by infrared thermal imager.The main conclusions are as follows:(1)When the laser is perforated in the air,as the current and pulse width increase,the slag accumulation increases,the recast layer becomes thicker,the ablation is serious and the microcrack becomes thicker and more obvious.The laser drilling in static solution,the above defects are smaller.(2)When laser drills a solution,both aqueous and saline solutions help improve the quality of the punch.The taper of the pores is effectively reduced,the roundness is increased,slag accumulation on the surface of the pores,the thickness of the recast layer,and the reduction of ablation and microcracking phenomena.Laser drilling holes in the air taper hole 15°,greater than the laser drilling in the static solution taper 11°.Laser drilling holes in the air,the hole roundness in addition to the current 210A(hole at the 230A)to achieve the best value of 0.95,the rest are below 0.9.When the laser is perforated in a static solution,the roundness of the hole is basically higher than 0.9,and the optimum value reaches above 0.99.Laser drilling holes in the air,hole surface slag accumulation height of 50?m above,and laser drilling in static solution,the hole surface slag height is only about 20?m,while the next hole deposition decreased significantly.The thickness of the recast layer is reduced from above 20?m(air hole)to about 10?m(hole in static solution).(3)By observing the fluctuation of the curve,when the laser is punctured in the sodium chloride salt solution,the change of the taper and the roundness of the hole is stable and regular with the change of the laser parameters,but the laser is more unstable in the drilling of the aqueous solution than in the salt solution.(4)Laser drilling in a static solution and a second punch,the secondary hole punch taper 11 ° to less than a hole punch taper about 13 °.However,roundness is flawed.That is,when the roundness of the hole drilled by one hole is high,the roundness of the second hole is reduced.When the roundness of the hole drilled by one hole is low,the roundness of the second hole is improve.In summary,laser drilling in static solution,the hole surface of the higher quality,slag deposition significantly reduced,through a simple clamping mechanism to complete the clamping,which can effectively improve the quality of laser drilling process.