Wear Patterns on Ball Bearings Lubricated by Grease Contaminated with Several Large Solid Particles

This study aims to investigate the wear patterns due to grease contamination by several types of solid particles on ball bearings. The research was conducted using a ball bearing test apparatus with a load of 300 N with a rotational speed of 2998 rpm for 4 hours. The solid contaminants used were iron sand, coal, silica, limestone, gypsum, and clay with a concentration of 20 wt% and particle sizes of 74 and 250 µm, respectively. During testing, the condition of the bearing and motor was monitored. Wear surface morphology was observed on the inner and outer races of the ball bearing using an optical microscope and SEM/EDX. The test results show that hard contaminants, such as silica and iron sand, predominantly induced abrasive wear through the two-body and third-body wear mechanism, resulting in scuffing and denting. While soft contaminants, such as coal, gypsum, clay, and limestone, primarily caused third-body wear mechanisms with flakes on the surface of the outer ring due to lack of lubricant properties and trigger starvation. SEM/EDX analysis confirms the role of two-body and third-body in accelerating wear progression. Monitoring the vibration, temperature, and current of the bearing and motor could identify the severity of wear.