Abstract
Electrochemical grinding (ECG) technique composed of electrochemical machining (ECM) and mechanical grinding is a proper method for machining of difficult-to-cut alloys. This paper presents a new ultrasonic assisted electrochemical drill-grinding (UAECDG) technique which combines electrochemical drilling, mechanical grinding, and ultrasonic vibration to fabricating high-quality small holes on superalloy. By applying ultrasonic vibration to high-speed rotating electrode in ECG, machining stability, efficiency, and surface quality can be obviously improved. Firstly, the electrochemical passive behavior of superalloy is studied, the mathematical model and simulation of gap electric field are established. Then, several experiments are conducted to investigate the influence of applied voltage, feed rate and ultrasonic amplitude on the machining quality. The balance of material removal between electrochemical reaction and mechanical grinding is achieved by optimizing the machining parameters. It reveals that the surface quality as well as machining stability and efficiency can be significantly improved by applying rotating ultrasonic vibration to the ECG process. Finally, several small holes of high quality have been machined successfully along with surface roughness of hole sidewall decreases from Ra 0.99 μm to Ra 0.14 μm by UAECDG.
Highlights
Nickel-based superalloys have been widely used in heated end components of aviation and aerospace engineering with advantages of high strength and toughness in elevated temperature, good oxidation resistance, excellent thermal stability, and fatigue properties [1,2,3]
This paper presents an ultrasonic assisted electrochemical drill-grinding (UAECDG) method in which rotating ultrasonic vibration is employed with Electrochemical grinding (ECG) for the fabrication of small holes with efficiency and precision
The rate relatedthe with the position of point of electrochemical reaction v machining time and θ isenergy, To maximize ultrasound output frequency of ultrasonic vibration is locked at the natural at point Qofisthe expressed as frequency tool electrode
Summary
Nickel-based superalloys have been widely used in heated end components of aviation and aerospace engineering with advantages of high strength and toughness in elevated temperature, good oxidation resistance, excellent thermal stability, and fatigue properties [1,2,3]. Due to the passive oxide film being much softer than metal materials, the machining efficiency is significantly increased and tool wear is avoided effectively compared with traditional grinding, especially for dealing with nickel-based superalloys and other difficult-to-cut alloys [17]. Proposed an electrochemical drill-grinding method for precision machining of small holes and found that the balance of ECM and mechanical grinding in ECG was the key to improve machining precision and surface quality [20]. Due to the mass electrolysis products and small machining gap in ECG of small holes, it is difficult to keep stability in ECG process and even cause a short circuit, which will cause low efficiency, poor surface quality, and excessive tool wear [20,22]. This paper presents an ultrasonic assisted electrochemical drill-grinding (UAECDG) method in which rotating ultrasonic vibration is employed with ECG for the fabrication of small holes with efficiency and precision. Small holes with high quality are machined successfully by optimized machining parameters
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