J Fail. Anal and Preven.(2012)12: 427-437 Fig& RS results of the greases: (a)fresh and(b)used Wavenumber (cm-1) 会 wavenumber (cm-1) During the operation of the air blower motor, the tem- perature of the roller bearing within the motor would be In order to characterize the solid substances in the greases, inevitably increased to some extent. Under this condition, KRD analyses were employed. As shown in Fig. 10a, the the grease used in the bearing suffered two kinds of deg fresh grease exhibits clear peaks of the Mos2 additives in radation, i.e., the decomposition and the oxidation. The the grease. However, complicated compounds such as former one would produce several low-molecular-weight Co3 ZnC appear in the used grease(Fig. 10b), which even organic compounds, and the latter one would generate contained the Zn element originally in the cage. Moreover, products with higher saturation, which were not easy to the Mosz peaks have disappeared, which further confirms decompose, i.e., the hardening effect. Only because of such the failure of the grease and the serious friction from degradations, the lubrication capacity of the grease had roller and the cage, and therefore the cages have bece deteriorated. Consequently, two harmful results were worn severely. brought about. On the one hand, with the decrease lubrication capacity, the lubrication mode between the roller and the outer ring changed from oil friction to the dry Discussion friction, which would certainly aggravate the extent of wear on the outer ring[9-12]. In addition, as the hardness Based on the analytic results of the fractured outer ring of of the outer ring was relatively lower than that of the roller, the cylindrical roller bearing and the used grease, origin of owing to its unqualified chemical compositions, the contact his fracture failure could be clearly put forward surface of the outer ring was destroyed and, with irregularXRD In order to characterize the solid substances in the greases, XRD analyses were employed. As shown in Fig. 10a, the fresh grease exhibits clear peaks of the MoS2 additives in the grease. However, complicated compounds such as Co3ZnC appear in the used grease (Fig. 10b), which even contained the Zn element originally in the cage. Moreover, the MoS2 peaks have disappeared, which further confirms the failure of the grease and the serious friction from the roller and the cage, and therefore the cages have become worn severely. Discussion Based on the analytic results of the fractured outer ring of the cylindrical roller bearing and the used grease, origin of this fracture failure could be clearly put forward. During the operation of the air blower motor, the tem￾perature of the roller bearing within the motor would be inevitably increased to some extent. Under this condition, the grease used in the bearing suffered two kinds of deg￾radation, i.e., the decomposition and the oxidation. The former one would produce several low-molecular-weight organic compounds, and the latter one would generate products with higher saturation, which were not easy to decompose, i.e., the hardening effect. Only because of such degradations, the lubrication capacity of the grease had deteriorated. Consequently, two harmful results were brought about. On the one hand, with the decrease of lubrication capacity, the lubrication mode between the roller and the outer ring changed from oil friction to the dry friction, which would certainly aggravate the extent of wear on the outer ring [9–12]. In addition, as the hardness of the outer ring was relatively lower than that of the roller, owing to its unqualified chemical compositions, the contact surface of the outer ring was destroyed and, with irregular Fig. 8 RS results of the greases: (a) fresh and (b) used 434 J Fail. Anal. and Preven. (2012) 12:427–437 123