1. RF9 Physics of Failure Sliding contact phenomena
Material related failure

2. RF9 Program Day 2
9:00-9:15 Introduction 9:15-9:30 Friction related failures 9:30-10:00 Demo load capacity of sliding contacts 10:00-10:15 Break 10:30-11:30 PoF Friction 11:30-11:45 Application of gained results 11:45-12:30 PoF Wear 12:30-13:30 Lunch 13:30-14:00 Demo Dry Sliding and EP additives 14:00-15:00 PoF Material selection  15:00-15:15 Break 15:15-16:15 PoF Lubrication 16:15-16:45 Application of gained results 16:45-17:00 Summary of the day
2013
RF9 - Physics of Failure

3. RF9 - Physics of Failure – Material Selection
Material & Coating Selection
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 222

4. RF9 - Physics of Failure – Material Selection
Case study Storm surge Barrier
A movable storm surge barrier is constructed making dikes along the river unnecessary.
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 222

5. RF9 - Physics of Failure – Material Selection
Case study Storm surge Barrier
F= Metric Tonnes Load
m= Metric Tonnes Load
p<150 MPa
µ<0.1
Material selection ?
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 222

6. RF9 - Physics of Failure – Material Selection
Material & Coating Selection
7.1 Materials in relative sliding
Metals, polymers, technical ceramics
7.2 Coatings and surface treatments
Surface treatments and classification
7.3 Material selection
Case study: storm surge barrier
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 222

7. PF9 - Physics of Failure – Material Selection
Material Selection: Metals
steel, bronze, cast iron…
2013
PF9 - Physics of Failure – Material Selection
Adv Eng Design Page 249

8. Severe adhesive friction / adhesive wear
Material Selection: Metals
Why metal-metal combinations are always lubricated.
Without lubrication:
Without lubrication
Severe adhesive friction / adhesive wear
Metals of relative high hardness:
Metals of relative low hardness:
+ Relative good wear resistance
(class 4)
High friction, scatter
(µ= )
+ Relative low friction
(µ= )
- High wear rate
(class 6)
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 249

9. Seminar - Physics of Failure
Case 1
2013
Seminar - Physics of Failure

10. RF9 - Physics of Failure – Material Selection
Material Selection: Metals
How to reduce friction and wear due to adhesion
Combinations of a non-metal against a metal
Carburizing or nitriding
High hardness of both surfaces
Difference in hardness of a factor between 3 to 5
High roughness
Strong oxide film
Lubricant, liquid or solid
Thin layer with low shear strength.
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 169

11. RF9 - Physics of Failure – Material Selection
Material Selection: Metals
How to reduce friction and wear due to adhesion
Combinations of a non-metal against a metal
Carburizing or nitriding
High hardness of both surfaces
Difference in hardness of a factor between 3 to 5
High roughness
Strong oxide film
Lubricant, liquid or solid
Thin layer with low shear strength.
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 169

12. RF9 - Physics of Failure – Material Selection
Material Selection: Polymers
µ(p,v)
Dependent on
heat conduction
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 209

13. RF9 - Physics of Failure – Material Selection
Material Selection: Polymers
Polymers
Thermoplastics
two types of thermoplastics
- crystalline
- amorphous
Thermosets
cannot be reshaped by heating
are stiff and strong in relation to thermoplastics
are often reinforced with glass or carbon fibers
Elastomers
rubbery polymers, can stretch easily and instantly return to its original shape when released.
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 309

14. RF9 - Physics of Failure – Material Selection
Material Selection: Polymers
Thermoplastics
+ Do not need to be lubricated
+ Low weight
+ Injection molding
- Low stiffness and strength
- Mechanical properties strongly depend on temp
- Poor heat conduction, large thermal expansion
- Large machining tolerances
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 309

15. RF9 - Physics of Failure – Material Selection
Material Selection: Polymers
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 253

16. RF9 - Physics of Failure – Material Selection
Material Selection: Polymers
Amorphous plastics
+ Less mold shrinkage
- Susceptible to chemical attack
- Lower wear resistance
Crystalline plastics
+ Higher strength and rigidity
+ Higher wear resistance
+ Good chemical resistance to oils and grease
(silicone based oils, water, soap…)
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 253

17. RF9 - Physics of Failure – Material Selection
Material Selection: Polymers
price
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 257

18. RF9 - Physics of Failure – Material Selection
Material Selection: Polymers
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 261

19. RF9 - Physics of Failure – Material Selection
Material Selection: Polymers
Self lubricating plastics are compounded with
- PTFE, MoS2, Graphite, Silicone oil, Aramid fibres
Fiber reinforced plastics are reinforced with
- Glass fibers, Carbon fibers
Steel counter surface
- HRc>50, Ra= μm
Aramid fibers
- Improves resistance to abrasion especially against counter surfaces of lower hardness such as aluminum and plastics.
The low friction is a result of a strongly adhering transfer film on the counter surface
Water lubrication precludes the formation of a dry lubricant film, resulting in high wear rate
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 260

20. RF9 - Physics of Failure – Material Selection
Material Selection: Polymers
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 258, 261

21. RF9 - Physics of Failure – Material Selection
Case 2
Bronze
St.50 (1.0050)
Pmax=10…20 MPa
Pmax=5…10 MPa
Failure mode:
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 222

22. RF9 - Physics of Failure – Material Selection
Material Selection: Metals
How to reduce friction and wear due to adhesion
Combinations of non-metals or a non-metal against a metal
Carburizing or nitriding
High hardness of both surfaces
Difference in hardness of a factor between 3 to 5
High roughness
Strong oxide film
Lubricant, liquid or solid
Thin layer with low shear strength.
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 169

23. RF9 - Physics of Failure – Material Selection
Material Selection: Metals
How to reduce friction and wear due to adhesion
Combinations of non-metals or a non-metal against a metal
Carburizing or nitriding
High hardness of both surfaces
Difference in hardness of a factor between 3 to 5
High roughness
Strong oxide film
Lubricant, liquid or solid
Thin layer with low shear strength.
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 169

24. RF9 - Physics of Failure – Material Selection
Material Selection: Metals
Difference in hardness of a factor between 3 to 5
Less tendency to adhesion (Pb, Sn)
Good embed ability for abrasive particles
Leveling out of stress concentrations
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 250

25. RF9 - Physics of Failure – Material Selection
Material Selection: Metals
Main bearing
Marine bearing
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 222

26. RF9 - Physics of Failure – Material Selection
Material Selection: Metals
Elastic support
Porous bearing
Oil circulation within the pores
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 210

27. RF9 - Physics of Failure – Material Selection
Material Selection: Metals
Porous iron
Hardened shaft
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 222

28. RF9 - Physics of Failure – Material Selection
Material Selection: Metals
Porous bronze (PbSn) bearings
μ= , k= m2/N, PV= Pa·m/s
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 222

29. RF9 - Physics of Failure – Material Selection
Case 3
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 306, 35, 221

30. RF9 - Physics of Failure – Material Selection
Material Selection: Metals
How to reduce friction and wear due to adhesion
Combinations of non-metals or a non-metal against a metal
Carburizing or nitriding
High hardness of both surfaces
Difference in hardness of a factor between 3 to 5
High roughness
Strong oxide film
Lubricant, liquid or solid
Thin layer with low shear strength.
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 169

31. RF9 - Physics of Failure – Material Selection
Material Selection: Metals
How to reduce friction and wear due to adhesion1) :
Combinations of a non-metal against a metal
Carburizing or nitriding
High hardness of both surfaces
Difference in hardness of a factor between 3 to 5
High roughness
Strong oxide film
Lubricant, liquid or solid 
Thin layer with low shear strength
Layered molecular structure of graphite
Stainless steel
Thin oxide layer
Stainless steel bolts require special purpose lubricants
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 169

32. RF9 - Physics of Failure – Material Selection
Case 3
AF-Coating
(MoS2, graphite)
Layered molecular structure of graphite
Successful application in clearance fits to prevent fretting corrosion (left) or galling (right)
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 306, 35, 221

33. RF9 - Physics of Failure – Material Selection
Material Selection: Metals
AF-Coating, P>100MPa, µ<0.1
Layered molecular structure of graphite
Particle orientation after initial sliding
AF-Coating
(MoS2, graphite)
Successful application in screw joints
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 306

34. RF9 - Physics of Failure – Material Selection
Material Selection: Metals
Layered molecular structure of graphite
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 309

35. RF9 - Physics of Failure – Material Selection
Material Selection: Metals
How to reduce friction and wear due to adhesion1) :
Combinations of non-metals or a non-metal against a metal
Carburizing or nitriding
High hardness of both surfaces
Difference in hardness of a factor between 3 to 5
High roughness
Strong oxide film
Lubricant, liquid or solid
Thin layer with low shear strength 
Galvanized
High corrosion resistance
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 169

36. RF9 - Physics of Failure – Material Selection
Material Selection: Metals
How to reduce friction and wear due to adhesion
Combinations of a non-metal against a metal
Carburizing or nitriding
High hardness of both surfaces
Difference in hardness of a factor between 3 to 5
High roughness
Strong oxide film
Lubricant, liquid or solid
Thin layer with low shear strength.
Case 4
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 169

37. RF9 - Physics of Failure – Material Selection
Material Selection: Tech. Ceramics
Al2O3 = Alumina
SiC = Silicon Carbide
Si3N4 = Silicon Nitride
ZrO2 = Zirconia
ZTA = Zirconia Toughened Alumina
+ High hardness and wear resistance
+ Low specific weight
+ Excellent high temperature properties
+ Resistance to corrosive environment
- Low toughness (brittle)
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 267

38. RF9 - Physics of Failure – Material Selection
Material Selection: Tech. Ceramics
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 151

39. RF9 - Physics of Failure – Material Selection
Material Selection: Tech. Ceramics
+ High resistance to abrasive wear (elastic deformation)
+ High resistance to adhesive wear (small γ/H ratio)
High surface energy but small ratio of surface energy and hardness
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 151

40. RF9 - Physics of Failure – Material Selection
Material Selection: Tech. Ceramics
Hydrodynamic bearing operating
in abrasive environment (Pavg= 6 MPa)
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 266

41. RF9 - Physics of Failure – Material Selection
Material Selection: Tech. Ceramics
Jewel bearings
Industrial jewels
Diamond pivots
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 504, 523

42. RF9 - Physics of Failure – Material Selection
Case 5
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 169

43. RF9 - Physics of Failure – Material Selection
Material Selection: Metals
How to reduce friction and wear due to adhesion
Combinations of non-metals or a non-metal against a metal
Carburizing or nitriding
High hardness of both surfaces
Difference in hardness of a factor between 3 to 5
High roughness
Strong oxide film
Lubricant, liquid or solid
Thin layer with low shear strength.
Case 5
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 169

44. RF9 - Physics of Failure – Material Selection
Material Selection: Coatings & surface treatments
Bonding strength
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 269

45. RF9 - Physics of Failure – Material Selection
Material Selection: Coatings & surface treatments
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 270

46. RF9 - Physics of Failure – Material Selection
Material Selection: Coatings & surface treatments
Advantage of dissimilar materials (Metallurgical incompatible materials).
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 268

47. RF9 - Physics of Failure – Material Selection
Introducing residual compressive stresses up to half the yield strength in order to improve the fatigue strength.
Shot peening also results in a work hardened surface improving the wear characteristics
Laser peening imparts a layer of compressive stress that is four times deeper than that attainable from conventional shot peening
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 273

48. PF9 - Physics of Failure – Material Selection
Material Selection: Coatings & surface treatments
Galvanizing - The article is immersed in a bath of molten zinc at between F ( C).
Nickel and chromium plating
2013
PF9 - Physics of Failure – Material Selection
Adv Eng Design Page 268

49. RF9 - Physics of Failure – Material Selection
Material Selection: Coatings & surface treatments
Laser cladding
Explosive welding is a solid state welding process, which uses a controlled explosive detonation to force two metals together at high pressure. Application multilayer bi-metal.
Laser cladding is an effective way to refurbish and improve worn or damaged industrial components
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 268

50. RF9 - Physics of Failure – Material Selection
Material Selection: Coatings & surface treatments
Pre-machining: removal of worn and with lubricant diffused material
Substrate low alloyed C-steel, Clad material
Stellite 21
Explosive welding is a solid state welding process, which uses a controlled explosive detonation to force two metals together at high pressure. Application multilayer bi-metal.
Post-machining to required dimensions
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 273

51. RF9 - Physics of Failure – Material Selection
Material Selection: Coatings & surface treatments
HVOF Spraying
Al2O3 TiO2 WC
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 270

52. RF9 - Physics of Failure – Material Selection
Material Selection: Coatings & surface treatments
CVD -TiN
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 273

53. RF9 - Physics of Failure – Material Selection
Material Selection: Coatings & surface treatments
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 274

54. RF9 - Physics of Failure – Material Selection
Material Selection: Coatings & surface treatments
Adhesive wear
(Galling)
DLC coatings in sheet metal forming, µ<0.1
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 268

55. RF9 - Physics of Failure – Material Selection
Material Selection: Coatings & surface treatments
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 275, 276

56. RF9 - Physics of Failure – Material Selection
Material Selection: Coatings & surface treatments
Summary
The wear resistance of a machine part is determined by the wear resistance of it’s surface.
This means that for the surface other demands can be made than for the bulk material
There are plenty of options to improve the surface quality
Treatments in the surface / on the surface
+ hard surface + tough core
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 275, 276

57. Case study Storm surge Barrier
Half of the Netherlands is below sea level. To prevent flooding dikes along the coast line are raised to delta level.
Raising the dikes along the river are unwanted and would be very expensive. A dam isn’t possible while the seaport of Rotterdam must remain accessible.
Adv Eng Design Page 275, 276

58. Adv Eng Design Page 275, 276

59. Adv Eng Design Page 275, 276

60. The lower sections are one point eight meters in diameter and the walls are nine centimeters thick.
Adv Eng Design Page 275, 276

61. The lower sections are one point eight meters in diameter and the walls are nine centimeters thick.
Adv Eng Design Page 275, 276

62. Adv Eng Design Page 275, 276

63. Adv Eng Design Page 275, 276

64. Adv Eng Design Page 275, 276

65. Adv Eng Design Page 275, 276

66. Adv Eng Design Page 275, 276

67. Adv Eng Design Page 275, 276

68. RF9 - Physics of Failure – Material Selection
Case study Storm surge Barrier
F= tonnes
m= tonnes
p<150 MPa
µ<0.1
Material selection ?
Hinge construction, the core consists of 20cm thick steel plates. The variation in hinges radius may not vary more than half a millimeter on a diameter of ten meters.
2013
RF9 - Physics of Failure – Material Selection

69. RF9 - Physics of Failure – Material Selection
Case study Storm surge Barrier
The allowable pressure in sliding contacts between metals is limited by seizure
Steel – cast iron 5…10 MPa, μ=0.12…0.18
Steel - CuSn or CuAl alloys 10…20 MPa, μ=0.12…0.18
In screw joints contact pressures up to 100 MPa are common, but the sliding motion is limited to one single move and μ=0.12…0.18
Zinc plated to prevent
corrosion and seizure.
The zinc plating of the screw is essential to prevent seizure.
2013
RF9 - Physics of Failure – Material Selection

70. RF9 - Physics of Failure – Material Selection
Solid lubricants
AF-Coating, P>100MPa, µ<0.1
Layered molecular structure of graphite
Particle orientation after initial sliding
AF-Coating
(MoS2, graphite)
Successful application in screw joints
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 306

71. RF9 - Physics of Failure – Material Selection
Case study Storm surge Barrier
Solid lubricants are used for conditions where
conventional lubricants are inadequate
Reciprocating motion, fretting
Improvement of running in conditions
Extreme contact pressures
Shock loading
High temperatures
Ceramics
2013
RF9 - Physics of Failure – Material Selection
Adv Eng Design Page 309

72. PF9 - Physics of Failure – Material Selection
Case study Storm surge Barrier
P<150MPa, µ<0.1
2013
PF9 - Physics of Failure – Material Selection
Adv Eng Design Page 307

73. RF9 - Physics of Failure – Material Selection
Case study Storm surge Barrier
What to do?
High maintenance costs
Adhesive wear between casting steel parts
How to prevent failure µ>0.1?
2013
RF9 - Physics of Failure – Material Selection

74. RF9 - Physics of Failure – Material Selection
Case study Storm surge Barrier
The problem: High maintenance costs (wear by seizure)
The challenge: Find a tribo system (material combination)
that sustains high contact pressures in sliding motion and
show minimal friction and minimal wear.
The solution: ?
2013
RF9 - Physics of Failure – Material Selection

75. RF9 - Physics of Failure – Material Selection
Case study Storm surge Barrier
The solution: ? Only limited possibilities to modify the realized construction.
Alternative lubricant or coating system?
Boundary Lubricated metal - metal contacts p<20MPa, µ>0.1
Thermoset – metal contacts p<150 MPa, µ>0.1
Polymer – metal contacts p<10 MPa, µ<0.1
2013
RF9 - Physics of Failure – Material Selection

76. RF9 - Physics of Failure – Material Selection
Case study Storm surge Barrier
Coulombs law:
If the load is doubled the friction is doubled.
Not for polymers!
Polymer – metal contacts only for limited contact pressure?
2013
RF9 - Physics of Failure – Material Selection

77. RF9 - Physics of Failure – Material Selection
Case study Storm surge Barrier
Cast steel with epoxy coating
UHMWPE
Cast steel
Carbon fiber
PE against epoxy resin, p>150 MPa, µ=0.02…0.06
F > 7000 kN (700 tonnes).
2013
RF9 - Physics of Failure – Material Selection

78. PF9 - Physics of Failure – Material Selection
Case study Storm surge Barrier
Testing of a special engineered turning cutter
2013
PF9 - Physics of Failure – Material Selection

79. RF9 - Physics of Failure – Material Selection
2013
RF9 - Physics of Failure – Material Selection

80. RF9 - Physics of Failure – Material Selection
500 holes in each ball joint
2013
RF9 - Physics of Failure – Material Selection

81. PF9 - Physics of Failure – Material Selection
2013
PF9 - Physics of Failure – Material Selection

82. RF9 - Physics of Failure – Material Selection
Case study Storm surge Barrier
Summary
The problem: High maintenance costs (wear by seizure)
The solution: Polymer discs, expansion blocked by carbon fiber rings, sliding against epoxy coated steel surface.
Performance: Contact pressures up to 150 MPa, coefficient of friction μ < 0.05, lifetime > 5 km sliding distance, maintenance limited to overhauling of the epoxy coating after a large number of moves.
2013
RF9 - Physics of Failure – Material Selection

83. RF9 - Physics of Failure – Material Selection
Summary
Several different material combinations have been discussed with respect to their applications.
Metals, metal alloys, thermoplastics, thermosets, ceramics and many coatings or surface treatments.
There is not an ideal material combination for sliding contacts in general.
In machine design metal-metal combinations are common and it is demonstrated that these combinations need to be lubricated.
2013
RF9 - Physics of Failure – Material Selection

84. RF9 Program Day 2
9:00-9:15 Introduction 9:15-9:30 Friction related failures 9:30-10:00 Demo load capacity of sliding contacts 10:00-10:15 Break 10:30-11:30 PoF Friction 11:30-11:45 Application of gained results 11:45-12:30 PoF Wear 12:30-13:30 Lunch 13:30-14:00 Demo Dry Sliding and EP additives 14:00-15:00 PoF Material selection 15:00-15:15 Break 15:15-16:15 PoF Lubrication 16:15-16:45 Application of gained results 16:45-17:00 Summary of the day
2013
RF9 - Physics of Failure