On surface quality and wear resistance of straight bevel gears finished by pulsed electrochemical honing process

Abstract

Pulsed electrochemical honing (PECH) is a hybrid super finishing process combining the process capabilities and advantages of mechanical honing with pulsed electrochemical machining (PECM) and simultaneously overcoming their individual limitations. This paper reports on influence of pulse parameters (i.e. pulse-on and pulse-off time) and finishing time on surface quality of PECH-finished straight bevel gears made of 20MnCr5 alloy steel. Average surface roughness, maximum surface roughness and surface roughness depth have been used to evaluate the surface finish while, bearing area curve, wear indicators (i.e. coefficient of friction and frictional force), microstructure and micro-hardness has been studied for the best finished gear. A gravimetric aqueous solution of 75% NaNO3 + 25% NaCl with a concentration of 7.5% was used as an electrolyte. It was found that 2 ms pulse-on time, 4.5 ms pulse-off time and finishing the gears for 6 min yielded the best combination of percentage improvements in average surface roughness, maximum surface roughness and roughness depth (i.e. 47.3 %, 46.9 % and 34.2 % respectively). Bearing area curve, wear indicators and micro-structure of the PECH-finished straight bevel gears also improved significantly while, micro-hardness remained unaffected. Such improvements in surface quality will enhance tribological fitness, service life, operating performance, mechanical efficiency and reduce noise and transmission errors in the bevel gears.