Laser Surface Texturing. Izhak Etsion Dept. of Mechanical Engineering Technion, Haifa Israel

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1 Laser Surface Texturing Izhak Etsion Dept. of Mechanical Engineering Technion, Haifa Israel

2 LST Regular Micro-Surface Structure in the Form of Micro-dimples

3 Hydrodynamic pressure distribution over a single protrusion F P a P a U P low U ; F = 0 high U ; F > 0 P a P c

4 Why dimples? - complicated etching technology - high wear - high leakage (seals) protrusions dimples - simple & cheap laser technology - lower wear - low leakage/spacing

5 Film Thickness and Geometry of of Micro-Dimples h 0 2r p h(x,z) h p U z x 2r 1 2r 1 dimensionless minimum clearance : δ = h ( 2r ) micro-dimple aspect ratio : ε = h p 0 (2r p p = h h = H dimensionless local film thickness : H 0 ) ( ε,δ )

6 A Mechanical Face Seal

7 Ring on Ring Scheme Rotating Ring without Laser Treatment Clearance Stationary Ring with Laser Treatment LOAD

8 Test rig arrangement

9 Friction Torque vs. Face Loading for Textured and Non-textured Seals in Water 25 Torque (in-lbs) Lapped Textured Unit load (psi)

10 Schematic of a partial laser surface textured mechanical seal h(x,z) h p c d i d p d o

11 Partial (on the Right) and Full (on the Left) Face Laser Texturing

12 Friction Torque vs. Sealed Pressure for Non-textured and Partial Textured Seals Untextured Torque [Nm] Textured Pressure [barg]

13 Field Test with Water Pump

14 Field Test with Water Pump

15 Pressure Distribution in a Stepped Slider (a), and in a Surface Textured Parallel Slider (b) P P U U a b

16 Results for Infinitely Long Slider. B = 50 ; δ = 0.2 ; Sp = 50% b p b U 12 Pav ε = 0.15 ε = 0.2 ε = 0.25 ε = 0.3 ε = 0.35 α

17 Bearing Mating Surfaces Showing a Textured Flat Stator and a Flat Rotor

18 Unidirectional (a) and a bi-directional (b) versions of the partial LST thrust bearing a b

19 Schematic of the Test Rig

20 Comparison of Partial LST Bearings and a Non-textured Bearing Friction at 1500 rpm Friction coefficient Bi-directional Untextured Unidirectional Load, N

21 Internal Combustion Engines Improved lubrication, speed and power Lower fuel consumption Reduced exhaust levels and operating temperatures Minimized cylinder wear and mechanical losses

22 Piston Group

23 Laser Textured Piston Ring Piston Textured Piston Ring Cylinder Liner

24 Laser Textured Piston Ring Textured Friction Surface Full Textured Piston Ring Segment Partially Textured Piston Ring Segment

25 Force Balance Engine P(τ) Cylinder Piston P e =P(τ)+P spring Combustion Chamber P(τ) P = 0 Piston Rings P h

26 Reciprocating Test Rig

27 Piston Rings Holder

28 Piston Rings and Cylinder Liner

29 Test Results Average Friction Force, N Untextured Fully textured Partially textured P= 0.3 MPa Angular Velocity, RPM

30 Ford transit engine on the test bench

31 Cross sections of cylindrical (a) and barrel shape (b) Cr coated piston rings (a) (b)

32 Partial LST cylindrical face piston ring

33 Engine specific fuel consumption vs. engine speed. Series 1: Barrel, chrome coated, baseline, Series 2: Flat, chrome coated, laser treated, Series 3: Flat, no chrome, laser treated Series 1 Series 2 Series 3 bsfc [(g-fuel/s)/(kw*hr)] Engine Speed [rev/min]

34 Piston

35 Piston pin and bearing

36 Tape moving over a LST guide

37 Impact of LST on Lubrication Regime Transition

38 Distribution of researchers by countries of origin Algeria Argentina Brazil Czech Republic Finland France Germany Greece Israel Japan Netherlands Poland Sweden Switzerland Turkey UK USA

39 Summary Laser surface texturing has emerged in recent years as a viable means of enhancing tribological performance. The laser is extremely fast, clean to the environment and provides excellent control of the shape and size of the micro-dimples, which allows realization of optimum designs. Several applications were shown to benefit from LST. These include dynamic sealing, thrust bearings, magnetic recording and internal combustion engines. Most of this work is still in a stage of theoretical modeling and laboratory testing. LST was successfully applied to mechanical seals resulting in up to 60% friction reduction and threefold increase in seal life in pumps operating in the field This success is attributed to the theoretical modeling of LST under full fluid film conditions, which gave good agreement with laboratory tests and permitted optimization of the LST parameters. It is envisaged that with the continuing R&D effort more applications may benefit from LST in the coming years.

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41 Comparison of Theoretical and Experimental Results of LST Mechanical Seal 0. 3 Average Pressure (MPa) Theoretical Experimental Clearance (µm)

42 Enlarged View of Rotor - Carbon Specimen Interface

43 Torque vs. Time (Baseline rotor) BASELINE ROTOR Torque Average Torque RPM RPM Torque (N-m * 100) RPM kPa 6.90kPa 10.34kPa 13.79kPa 17.24kPa 20.68kPa 24.13kPa 27.58kPa 34.47kPa RPM ELAPSED TIME (MINUTES)

44 Torque vs. Time (LST rotor) ROTOR w/ LST Torque Average Torque RPM RPM TORQUE (N-m * 100) kPa 6.90kPa 10.34kPa 13.79kPa 17.24kPa 20.68kPa 24.13kPa 27.58kPa 34.47kPa ELAPSED TIME (MINUTES) RPM RPM

45 Average Torque vs. Time, Comparison of Baseline & LST Rotors at 12,000 rpm 12 BASELINE & LST ROTORS 3.45 kpa 6.90 kpa kpa kpa kpa kpa 10 TORQUE (N-m * 100) BASELINE ROTOR LST ROTOR kpa 6.90 kpa kpa kpa kpa kpa ELAPSED TIME (MINUTES)

46 Typical Pressure Distributions and Maximum Load Capacity Tapered W=0.16 Stepped W= < S p < 0.65 Parallel LST W=0.16S p

47 A Comparison of Partial LST Bearing and Non-textured Bearing Performance n = 3000 rpm Textured Nontextured Clearance, µm n = 1500 rpm Load, N