J Fail. Anal and Preven.(2011)11: 158-16 ZEKE 1,9818从m 26/NoU/85 ) C 1200 0 1800 SMo 600 SMo (b) Fig 5 SEM and EDS of the used grease sample (a)SEM micrograph ig. 4 SEM and EDS of the fresh grease sample. (a)SEM micro- and (b) EDS analysis )EDS analysis containing copper, would further accelerate the oxidation MoS2 diffraction peaks was decreased significantly in XRD of the base oil and thickener, and consequently degraded atterns of the used grease sample, as shown in Fig. 3b grease[9] [9]. Actually, the metallic elements Cu, Zn, Fe it, the strongest diffraction peak(20= 42, d=0.21 nm) etc. in the used grease were mainly derived from the could be attributed to(110) crystalline plane of the Cu-Zn bearing (ring or roller)and the cage materials (Cu, Zn intermetallic (identified by PDF cards ). At the same time, alloy ). That is to say, the roller bearings had suffered a the weak diffraction peaks of Fe Cr2O4 (about 20= 36, serious extent of wear. With regard to MoS2 diffraction d=0.25 nm, 20= 56, d=0.16 nm, etc. also existed in peaks being weakened in XRD curve of the used grease Fig. 3b. It revealed that the used grease sample was a sample, it suggested that the contents of Mos2 particulates omplex mixture of compounds like MoS2, Cu-Zn inter- in the used grease had decreased since the content of met metallic, FeCr2O4, and so on. Figure 5a shows sEM debris increased in the grease. Thus, the relative value of icrograph of the used greases. Compared to the micro- the Mos, content was reduced. In addition, another factor graph of the fresh grease(Fig. 4a), it is obvious that may be that part of the MoS2 particulates had been disso- were a large amount of irregular particulates in the ciated from the grease and agglomerated on the raceways greases. The EDS analysis of different particulates showed due to loss of the grease network structure induced by that these particulates mainly contained elements like Cu, thermal degradation/oxidation Zn, Fe, Mo, S, etc(see Fig 5b). It can be inferred that the The above analysis demonstrated that the phase com- uneven particulates were resulted from agglomeration of ponents of the used grease samples were quite different different compounds made from these elements, which with that of fresh ones. The structure of the grease in was consistent with above XRD results of the used grease. bearing had significantly changed during the bearing The presence of metallic particulates, particularly those operationMoS2 diffraction peaks was decreased significantly in XRD patterns of the used grease sample, as shown in Fig. 3b. In it, the strongest diffraction peak (2θ = 42°, d = 0.21 nm) could be attributed to (110) crystalline plane of the Cu–Zn intermetallic (identified by PDF cards). At the same time, the weak diffraction peaks of FeCr2O4 (about 2θ = 36°, d = 0.25 nm, 2θ = 56°, d = 0.16 nm, etc.) also existed in Fig. 3b. It revealed that the used grease sample was a complex mixture of compounds like MoS2, Cu–Zn inter￾metallic, FeCr2O4, and so on. Figure 5a shows SEM micrograph of the used greases. Compared to the micro￾graph of the fresh grease (Fig. 4a), it is obvious that there were a large amount of irregular particulates in the used greases. The EDS analysis of different particulates showed that these particulates mainly contained elements like Cu, Zn, Fe, Mo, S, etc. (see Fig. 5b). It can be inferred that the uneven particulates were resulted from agglomeration of different compounds made from these elements, which was consistent with above XRD results of the used grease. The presence of metallic particulates, particularly those containing copper, would further accelerate the oxidation of the base oil and thickener, and consequently degraded the grease [9]. Actually, the metallic elements Cu, Zn, Fe, etc. in the used grease were mainly derived from the bearing (ring or roller) and the cage materials (Cu, Zn alloy). That is to say, the roller bearings had suffered a serious extent of wear. With regard to MoS2 diffraction peaks being weakened in XRD curve of the used grease sample, it suggested that the contents of MoS2 particulates in the used grease had decreased since the content of metal debris increased in the grease. Thus, the relative value of the MoS2 content was reduced. In addition, another factor may be that part of the MoS2 particulates had been disso￾ciated from the grease and agglomerated on the raceways due to loss of the grease network structure induced by thermal degradation/oxidation. The above analysis demonstrated that the phase com￾ponents of the used grease samples were quite different with that of fresh ones. The structure of the grease in bearing had significantly changed during the bearing operation. Fig. 4 SEM and EDS of the fresh grease sample. (a) SEM micro￾graph and (b) EDS analysis Fig. 5 SEM and EDS of the used grease sample. (a) SEM micrograph and (b) EDS analysis 162 J Fail. Anal. and Preven. (2011) 11:158–166 123