Academic Journal of Science and Technology ISSN: 2771-3032 | Vol. 7, No. 1, 2023 1 Effect of Discharge Parameters on Surface Roughness and Material Removal Rate of GH4169 High Temperature Alloy by WEDM Mingming Xu Institute of Mechanical and Electrical Engineering, Lingnan Normal University, Zhanjiang, 524048, China Abstract: GH4169 high-temperature alloy is a difficult-to-machine material commonly used in the aerospace industry. The surface roughness and material removal rate are important indicators in the production of WEDM processing GH4169 high- temperature alloy, and the discharge parameters directly affect the surface roughness and material removal rate. Several groups of optimized discharge parameters were used to process GH4169 high temperature alloy, and the specific influence of each discharge parameter on the surface roughness and material removal rate was obtained respectively. The results of the study provide a technical reference for the production of WEDM processing GH4169 high-temperature alloy, and a suitable combination of discharge parameters can be selected according to different production requirements. Keywords: WEDM, GH4169 high temperature alloy, Discharge parameters, Surface roughness, Material removal rate. 1. Introduction GH4169 high-temperature alloy is a difficult-to-machine material with high hardness and high toughness, and the material hardness reaches more than HRC56 after heat treatment. In the aerospace industry, WEDM is commonly used to process GH4169 high-temperature alloy to make complex parts. When WEDM processing GH4169 high- temperature combined, the discharge parameters (processing current, pulse width, pulse interval) affect the surface roughness and material removal rate of the material, which are important indicators of the machined surface quality and processing efficiency, respectively, as well as a pair of mutually constraining technical indicators [1]. The effect of WEDM on the surface roughness and material removal rate has been studied by many scholars [2-6]. Other scholars [7- 10] have used orthogonal test methods to optimize the discharge parameters of WEDM processing of high- temperature alloys. In this paper, we will use EDM wire- cutting equipment to process GH4169 high-temperature alloy with three sets of optimized discharge parameters to observe and study the effects of various discharge parameters on the surface roughness and material removal rate of the processed material. 2. Experiment 2.1. Experimental materials The size of the specimen in the experiment is 10×10×100mm, and the hardness reaches HRC56 after heat treatment; all surfaces of the specimen are pre-machined with a surface grinder to a surface roughness of Ra0.8μm. 2.2. Specimen preparation DK7740 WEDM machine was used to process the specimens, and the electrode wire diameter was φ0.12mm molybdenum wire; the cutting fluid was emulsion of 2wt% concentration; the processing method was one time cutting. Different discharge parameters were used to process the specimens on the WEDM machine, and the specimens were cut to a thickness of 6 mm, and then the specimens were cleaned by ultrasonic waves for 10 min to remove the stains and attached electrolytes on the surface of the specimens. The discharge parameters are shown in Table 1, 2 and 3. Table 1. Different processing current parameters processing current parameter I (A) pulse width parameter W (μs) pulse interval paramete J (μs) processing voltage V (V) speed of the line S (m/min) 1.0、1.4、1.6、2.0、 2.4、2.6、2.8、3.0 12 10 80 12 Table 2. Different pulse width parameters processing current parameter I (A) pulse width parameter W (μs) pulse interval paramete J (μs) processing voltage V (V) speed of the line S (m/min) 2.0 6、8、10、12 14、16、18、20 10 80 12 2 Table 3. Different pulse interval parameters processing current parameter I (A) pulse width parameter W (μs) pulse interval paramete J (μs) processing voltage V (V) speed of the line S (m/min) 2.0 12 6、8、10、12 14、16、18、20 80 12 2.3. Measurement of surface roughness and material removal rate Using a roughness meter to measure the surface roughness of the specimen after the WEDM process, the material removal rate is calculated using the formula: MRR (mm2.min-1)=S (mm2)/t (min) Material removal rate: MRR; Processing cross-sectional area: S Processing times: t In the experiments, the WEDM machine system comes with the machining time statistics function, and the machining cross-sectional area S is fixed at 100 mm2. 3. Results and Analysis 3.1. Effect of different processing currents on surface roughness The machining current is an important factor affecting the surface properties of the material processed. The processing current increases, the pulse energy increases, the ability to etch the material per unit time increases, and the cutting speed is accelerated, but too much current tends to cause processing instability, which will produce the phenomenon of wire breakage. Under the experimental conditions of processing current 1.0, 1.4, 1.6, 2.0, 2.4, 2.6, 2.8, 3.0A; pulse width 12μs, pulse gap 10μs, the surface roughness of the machined specimen reached Ra1.58, 1.69, 1.80, 2.27, 2.96, 3.48, 4.38, 4.99 respectively, with an increasing trend, and in the processing The surface roughness of the processed surface increased significantly after the current was greater than 1.6A. The material removal rate reached 10.2, 12.9, 13.9, 14.9, 20.8, 29.4, 35.8, 43.4 mm2/min, which was consistent with the surface roughness and showed an increasing trend, and the material removal rate increased significantly after the processing current was greater than 2.0A. 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Processing Current I/A Su r f a ce R ou g h ne s s R a / μ m 5 10 15 20 25 30 35 40 45 50 M MR / m m2 . m i n - 1 → ← Figure 1. Surface roughness and materical removal rate with different processing current parameters With the increase of processing current, processing pulse energy enhancement, material surface galvanic corrosion phenomenon is obvious, electrode wire and GH4169 high- temperature alloy specimen high frequency discharge instantaneous high temperature generated by the material surface vaporization and dissolution of the formation of compounds, these compound gases and cooling condensation under the action of the coolant, a small part of the fusion coating on the processing surface to form a recast layer, most of the electro-etching material into fine particles with the cutting fluid was discharged; the higher the processing current, the more surface fusion coating, recast layer thickness is greater, the surface produced more bumps and depressions, the surface roughness becomes worse. 3.2. The effect of different pulse width on surface roughness Pulse width refers to the pulse power discharge time, and the pulse width value can be increased according to the actual situation when processing a workpiece with large thickness. Under the experimental conditions of processing current 2.0A, pulse width 6, 8, 10, 12, 14, 16, 18, 20μs; pulse gap 10μs, the surface roughness of the processed specimens reached Ra1.81, 1.89, 1.96, 2.36, 2.96, 3.88, 4.21, 4.52 respectively, with an increasing trend. The material removal rate reached 10.5, 11.9, 12.5, 14.9, 17.8, 26.5, 34.9, and 48.8 mm2/min, which were consistent with the surface roughness and showed an increasing trend, and the material removal rate increased significantly after the pulse width was greater than 12 μs. 3 4 6 8 10 12 14 16 18 20 22 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Pulse Width W/μs Su r fa c e Ro ug h ne s s R a/ μ m 5 10 15 20 25 30 35 40 45 50 M MR /m m2 .m in - 1 → ← Figure 2. Surface roughness and Materical Removal Rate with different pulse width parameters As the pulse width increases, the individual pulse energy is enhanced. The larger the pulse width, the more surface cladding, the more recast layer thickness increases, the more surface convexity, and the surface roughness becomes worse, but the effect of pulse width on surface roughness is slightly less than the effect of processing current on surface roughness. 3.3. The effect of different pulse interval on surface roughness The pulse interval is the pulse stopping time, the pulse gap decreases, the number of cuts per unit time increases and the cutting speed is accelerated, but too small a pulse interval will easily ablate the electrode wire causing wire breakage; and too small pulse interval is not conducive to the discharge of galvanic corrosion, resulting in unstable processing; and too large a pulse interval will lead to discontinuous feeding and slow cutting speed. Under the experimental conditions of 2.0A processing current, 12μs pulse width, 6, 8, 10, 12, 14, 16, 18 and 20μs pulse interval, the surface roughness of the processed specimens reached Ra2.93, 2.64, 2.42, 2.37, 1.92, 2.23, 1.99 and 2.14 respectively, which showed a trend of decreasing and then small fluctuation towards smoothness. The material removal rate reached 32.6, 23.4, 19.5, 16.7, 14.2, 12.9, 11.2, and 10.7 mm2/min, respectively, with a decreasing trend, and the material removal rate slowed down after the pulse interval was greater than 10 μs. 4 6 8 10 12 14 16 18 20 22 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Pulse Interval J/μs S ur fa ce R ou gh n es s Ra /μ m 5 10 15 20 25 30 35 MM R/ mm 2 . mi n- 1 → ← Figure 3. Surface roughness and materical Removal Rate with different pulse interval parameters 4. Conclusions The WEDM processing of GH4169 high temperature alloy, the discharge parameters directly affect the surface roughness and material removal rate of the machined material. The surface roughness and material removal rate increase simultaneously with the increase of processing current and the trend is similar; the surface roughness and material removal rate increase simultaneously with the increase of pulse width; the material removal rate is decreasing, the surface roughness of the processed material decreases in the early stage, and the decreasing trend slows down after the pulse interval 10μs, and reaches the minimum value at the pulse interval 14μs, and slightly increases after the pulse interval more than 10μs, the change is not significant.In the process of GH4169 high temperature alloy, the influence of discharge parameters on surface roughness is from the largest to the smallest: processing current, pulse width, pulse interval; the influence of discharge parameters on material removal rate is from the largest to the smallest: pulse width, processing current, pulse interval. 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