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Study of Wear in a Novel Cu-Based Sintered Alloy for Train Brakes (Influence of Sintered Temperature)

作　者: Glenn Kwabena Gyimah
导　师: 黄平
学　校: 华南理工大学
专　业: 机械设计及理论
关键词: Copper matrix Friction material Wear mechanism Train brake pad
分类号: U270.35
类　型: 硕士论文
年　份: 2010年
下　载: 33次
引　用: 0次
阅　读: 论文下载

内容摘要

A novel Cu-based composite frictional train brake material composed of several elements such as Al, SiO2, Fe, graphite, Sn, Mn and MoS2 re-enforced with other elements was treated under Powder Metallurgy (P/M) route. Well prepared powders were hydraulically compacted at 650MPa. The materials were sintered at three different temperatures (850oC, 900oC and 950oC) at a constant pressure. The dry sliding friction and wear characteristics of three different sintering treatment temperatures were investigated and the results were remarkable.The tribological behavior of these materials was analyzed by pad-on-disk tests without lubrication and the coefficient of friction, wear rate and wear number were studied in order to identify the effects of the sintering temperature on the base materials composition. The porosities were found to be very high but were adequate to give the right self lubrication properties and to reduce seizure. It was found that the porosity varies inversely proportional to the increase in sintering temperature. The pores in the sintered material were mainly solid lubricants such as graphite and other low melting elements. This also resulted in poor hardness and mechanical properties, which were compensated by its ability to reduce seizure. Much lower wear frictional coefficient, k and the highest coefficient friction,μwith a high wear number, Wn were obtained, indicating a good wear resistance property of the friction material.Three forms of wear mechanisms were observed during the dry sliding process, namely; delamination wear, plowing wear and abrasive wear. The abrasive wear results in flake or break-away debris. These wear mechanisms were found to be responsible for high wear rates on samples sintered at 850oC and 900oC. Generally, the materials demonstrated excellent brake performance and wear resistance. The average values of friction coefficient under excessive pressure (3.13MPa) dry conditions were 0.336, 0.343, and 0.404, at 850oC, 900oC and 950oC respectively.The results show that the main components of worn surface are graphite, SO2, Fe, Cu and oxides of Fe and Cu (Fe203 and CuO) and AlFe. The worn surfaces were divided into three sections: destructive wear section, medium wear section and low wear section. These wear mechanisms were examined by using SEM and XRD. TALYSURF CLI 1000 was also used to classify the varieties of observed abrasive surfaces. The surfaces observed were also classified into three categories based on the degree of surface destruction during the braking process. These are as follows: smooth abrasive surface (mirror surface and integrated friction film; rough abrasive surface (rough surface); highly abrasive surface (much rough surface) showing more excessive wear than the former.

全文目录

Abstract  5-10
Chapter 1 Introduction  10-15
  1.1 The Complexity  10-12
  1.2 The Problem Statement  12-13
  1.3 Research Goals and Approaches  13-14
  1.4 The Challenges  14-15
Chapter 2 Literature Review (Brakes)  15-36
  2.1 Mechanical Braking System  16
  2.2 Friction Materials  16-18
  2.3 Brake Materials and Additives Functional  18-20
    2.3.1 Abrasives  18-19
    2.3.2 Friction Producers / Modifiers  19
    2.3.3 Fillers, Reinforcements and Miscellaneous  19
    2.3.4 Binder (Matrix) Materials  19
    2.3.5 Asbestos  19-20
  2.4 Brake Friction Designations and Typical Compositions  20
  2.5 Friction Brake Compositions for Aircraft and Ground Vehicles  20-31
    2.5.1 Aircraft Brake Formulations  21-23
    2.5.2 Automotive Brake Pad Formulations  23-29
    2.5.3 Passenger Car and Truck Brake Disc and Drum Materials  29-31
  2.6 Understanding Wear  31-35
  2.7 In Summary  35-36
Chapter 3 Materials and Methods  36-50
  3.1 Brake and Materials  36-37
  3.2 Methods  37-38
  3.3 Design  38-40
    3.3.1 Aim  38
    3.3.2 Task  38
    3.3.3 Die and Two Steel Punches  38-40
    3.3.4 Specimen Holder  40
  3.4 Sample Preparation  40-43
    3.4.1 Powder selection  40-41
    3.4.2 Mixing of Powder  41-42
    3.4.3 Compacting of Powder  42
    3.4.4 Sintering  42-43
  3.5 Testing Procedures  43-48
    3.5.1 Characterization Test  43-44
    3.5.2 Performance Test  44-47
    3.5.3 Microstructure Analysis  47
    3.5.4 Density  47-48
    3.5.5 Disc Material  48
    3.5.6 Test Conditions  48
  3.6 In Summary  48-50
Chapter 4 Experimental Results  50-66
  4.1 Temperature Effect on Mechanical Behaviors  50-55
    4.1.1 Density and Porosity  50-54
    4.1.2 Hardness  54-55
  4.2 Tribological Behaviors  55-65
    4.2.1 Microstructure of the material  56-58
    4.2.2 Frictional Behaviors  58-59
    4.2.3 Wear Behaviors  59-62
    4.2.4 Worn Surface  62-63
    4.2.5 Worn surfaces characteristics with XRD and SEM  63-64
    4.2.6 Abrasive Surfaces Classification with TALYSURF  64-65
  4.3 In Summary  65-66
Chapter 5 Results Analysis  66-74
  5.1 Mechanical Behaviors  66-67
    5.1.1 Density and Porosity  66-67
    5.1.2 Hardness  67
  5.2 Tribological Behaviour  67-73
    5.2.1 Microstructure of the material  67-68
    5.2.2 Frictional Behaviours  68-69
    5.2.3 Wear Behaviours  69
    5.2.4 Worn Surface  69-71
    5.2.5 Worn surfaces characteristics with XRD and SEM  71-72
    5.2.6 Abrasive Surfaces Classification with TALYSURF  72-73
  5.3 In Summary  73-74
Chapter 6 Conclusions and Future Work  74-77
  6.1 Conclusions  74-76
  6.2 Future Work  76-77
References  77-80
攻读硕士学位期间取得的研究成果  80-81
Acknowledgements  81

Study of Wear in a Novel Cu-Based Sintered Alloy for Train Brakes (Influence of Sintered Temperature)

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