Investigations on surface roughness and tribology of miniature brass gears manufactured by abrasive water jet machining

Surface roughness parameters are important indicators for determining the operating performance, tribology behavior, wear and tear characteristics, and service life of engineered parts including gears. This article presents the investigation on surface roughness, and tribology and wear aspects of miniature brass gears manufactured by abrasive water jet machining. Experiments have been conducted based on Taguchi's robust design technique with L₉ orthogonal array to machine external spur-type miniature gears of brass having 8.4 mm pitch diameter, 12 teeth, and 5 mm thickness. The effect of three important process parameters namely water jet pressure, abrasive mass flow rate, and stand-off distance on mean roughness depth of miniature gears are analyzed. Surface roughness is found to decrease with the increase in the water jet pressure and abrasive mass flow rate, and increases with the increase in the stand-off distance. Particle swarm optimization technique has been used for parametric optimization to minimize the surface roughness of miniature gears. Confirmation experiment conducted at optimized abrasive water jet machining parameters resulted in superfine surface finish with mean roughness depth value of 4.1 µm superior than the finish obtained by other advanced processes for brass gears. The investigated values of bearing area characteristics, skewness, kurtosis, and friction coefficient confirm the tribological fitness of the miniature brass gear machined at optimum abrasive water jet machining parameters.