Investigations on laser lay profiling on surface quality and microgeometry of spur gears for finishing by AFF

Abstract

Higher wear resistance, lower noise level, enhance power transmission capability, better transmission efficiency, operating performance and longer service life are continuously growing expectations from the gears. These expectations can be met by manufacturing the gears of better quality. Manufacturing of better quality gears requires minimizing errors or deviations in microgeometry parameters, surface roughness parameters and improving surface integrity (i.e. residual stresses, microstructure, microhardness etc.) of the gear flank surfaces by appropriate gear finishing process.Laser surface texturing provides micro-reservoirs to enhance lubricant retention or micro-traps to capture wear debris. Presence of micro-texture improves friction and wear characteristics of materials. But, it arises excess melt material on the surface as an artifact from the laser processing. These melt and excess re-solidified material need to be removed through finishing methods to achieve intended surface geometry and quality. Abrasive flow finishing (AFF) is an advanced finishing process. Present work is focused on investigating the effect of laser lay profiling on microgeometry and surface quality of 20MnCr5 alloy steel spur gears finished by AFF process. Homothetic textured lay profile was created by laser beam of 1064nm wavelength on the hobbed spur gears in direction normal to lay profile by hobbing and later it was finished by AFF process. The finishing performance of hobbed spur gears and laser lay profiled hobbed spur gears by AFF in terms of microgeometry deviations (i.e. profile, lead, pitch and runout), surface quality(i.e. average surface roughness, maximum surface roughness), material removal rate, microhardness and wear rate were compared. Extrusion pressure of 5 MPa, finishing time of 25 minutes and abrasive particle (SiC) of mesh size 100 with 30 % weight concentration produced the best surface quality gear. This research shows the maximum percentage reduction in average surface roughness (PRRa), maximum surface roughness (PRRmax), total profile error (PRFa), total lead error (PRFb), cumulative pitch error (PRFp), and runout error (PRFr) as 69.12%, 68.92%, 28.49%, 40.20%, 24.85%, 4.80% respectively for laser lay profiled spur gear finished by AFF which is more as compared to 61.27%, 48.14%, 21.55%, 38.97%, 15.95%, 3.93% respectively for spur gear directly finished by AFF. Higher improvement is observed in microgeometry, surface quality, material removal rate, microhardness and wear resistance for finishing of hobbed spur gear with laser lay profiling by AFF process as compared to finishing of hobbed spur gear with laser lay profiling by AFF with same finishing time. This will increase operatingperformance and service life of gears which prevent premature failure, low running noise and vibration.