CARBONITRIDING & NITROCARBURIZING. Comparative study on tribological behaviours

Transcription

1 Page 1 JIFT 2012 Intérêt tribologique de la nitrocarburation CARBONITRIDING & NITROCARBURIZING Comparative study on tribological behaviours Pierre-François CARDEY - Alexandre FLEURENTIN Department Metallic Materials & Surfaces

2 N2M 2014 Carbonitriding & Nitrocarburizing Summary Page 2 BACKGROUND MATERIALS AND TREATMENTS STUDIED EXPERIMENTATION BEHAVIOR IN LUBRICATED ENVIRONMENT Comparison carbonitriding / nitrocarburazing Influence of the compound layer BEHAVIOR IN DRY ENVIRONMENT Comparison carbonitruration / nitrocarburation Influence of the compound layer CONCLUSIONS

3 N2M 2014 Carbonitriding & Nitrocarburizing Page 3 BACKGROUND

4 Background Background Page 4 Two thermochemical treatments, using the diffusion of carbon and nitrogen, to the surface hardening of steel parts: Carbonitriding Nitrocarburizing C C ~600 C C Quench hardening (martensitic formation) Precipitation hardening (nitrides and carbonitrides) - Compound layer on surface (iron nitrides) - Smaller case depth - Lower process temperature

5 Background Objectives Page 5 Multi-partner project of CETIM: Help manufacturers to choose between nitrocarburizing and carbonitriding Study on the tribological behaviour of these thermochemical treatments: Friction and wear in dry condition Friction and wear on lubricated environment

6 N2M 2014 Carbonitriding & Nitrocarburizing Page 6 MATERIALS AND TREATMENTS STUDIED

7 Materials and treatments Materials and treatments studied Page 7 Steel grade 27MnCr5 quenched-tempered to 33HRC 1 Carbonitring 8 Nitrocarburizing Compound layer: Oxyde layer (Fe 3 O 4 ) Diffusion zone Nitride ε (Fe (2,3) N) Nitride γ (Fe 4 N) Case depth: 0,64 mm (at 650 HV) Diffusion zone: 0,2-0,3 mm Compound layer: 8 different architectures

8 Materials and treatments Compound layers architectures Page 8 White layer with a columnar porosity Nit-3 Dense white layer Nit-2 Nit-4 Nit-5 White layer with a globular porosity Nit-1 Nit-6 Nit-7 Nit-8

9 Materials and treatments Metallurgical caracteristics of the nitrocarburizing treatments Page 9 Ref Depth of the diffusion zone (µm) HV core Depth of the compound layer (µm) XRD analysis Iron oxyde layer Fe 3 O 4 Post-oxydation Porosity of the compound layer Tenacity of the compound layer Vickers indentation HV30 Nit ,5 Yes Globular Good Nit ,8 No No porosity Good Nit ,4 Yes (thick) Columnar Good Nit ,7 Yes No porosity Medium Nit-5 ~ ,0 Yes No porosity Medium Nit ,6 Yes Globular Low Nit-7 ~ ,2 Yes Globular Low Nit ,9 Yes Globular Low Good tenacity Low tenacity

10 Materials and treatments Surface caracteristics of the thermochemical treatments Page 10 Ref Ra (µm) Roughness Rsk Wettability (α angle) (lubricant of the friction test) Initial 0,25-0,33 - Wettability Roughness measuring direction Carb 0,28 0,07 16,18 Nit-1 0,31-0,23 11,74 Nit-2 0,30-0,30 11,26 Grinding roughness Nit-3 0,35 0,01 10,85 Nit-4 0,32-0,30 12,07 Nit-5 0,37-0,20 16,74 Nit-6 0,37-0,25 14,83 Nit-7 0,26-0,18 15,49 Nit-8 0,38 0,31 22,66 Roughness

11 N2M 2014 Carbonitriding & Nitrocarburizing Page 11 EXPERIMENTATION

12 Experimentation Plint TE-77 tribometer Page 12

13 Experimentation Test conditions Page 13 - Contact mode: Cylinder Ø8 crossing cylinder Ø60 - Load (F N ): F N 100 N (P max = MPa ; P moy = 955 MPa) 20 N (P max = 830 MPa ; P moy = 560 MPa) - Stroke: 15 mm - Frequency: 10 Hz (average velocity: 0,3 m.s -1 ) 1 Hz (average velocity: 0,03 m.s -1 ) - Friction distance: 200 m - Environment: lubrication (Oil Total LDS) dry(only 20N 1Hz)

14 N2M 2014 Carbonitriding & Nitrocarburizing Page 14 BEHAVIOURS IN LUBRICATED ENVIRONMENT

15 Results Lubricated contact Evolution of the coefficient of friction in lubricated environment Page 15 F N = 20 N ; v = 0,03 m.s -1 F N = 100 N ; v = 0,03 m.s -1

16 Results Lubricated contact Evolution of the coefficient of friction in lubricated environment Page 16 F N = 20 N ; v = 0,3 m.s -1 F N = 100 N ; v = 0,3 m.s -1

17 Results Lubricated contact Electrical contact resistance (ECR) measurment Page 17 PIN No lubricant film contact PIN Presence of lubricant film No contact PLATE PLATE No lubricant film: there is a contact between the surfaces: ECR = 0 Presence of lubricant film: there is no contact between the surfaces: ECR = ECR max

18 Results Lubricated contact µ and ECR evolution Page 18 Decrease of the coefficient of friction at the establishment of the lubricant film. Initiation distance of lubricant film

19 Results Lubricated contact Initiation distance of lubricant film Page 19 Initiation distance of lubricant film (Total LDS ; 1 Hz / 15 mm ; 20 N) 120,00 Amorce Initiation de la lubrification distance EHD of lubricant (fluide Total film FDS ; (Total 10 LDS Hz sur ; 1015 Hz mm / 15 ; mm 20 N) ; 20 N) 100,00 Distance (m) 80,00 60,00 40,00 20,00 0,00 Carb Nit-1 Nit-2 Nit-3 Nit-4 Nit-5 Nit-6 Nit-7 Nit-8 F N = 20 N ; v = 0,03 m.s -1 F N = 100 N ; v = 0,03 m.s -1

20 Results Lubricated contact Initiation distance of lubricant film Page ,00 Amorce Initiation de la lubrification distance EHD of lubricant (fluide Total filmfds ; (Total 1 LDS Hz sur ; 115 Hz mm / 15 ; 100 mm N) ; 100 N) Initiation distance of lubricant film (Total LDS ; 10 Hz / 15 mm ; 100 N) 100,00 80,00 Distance (m) 60,00 40,00 20,00 0,00 Carb Nit-1 Nit-2 Nit-3 Nit-4 Nit-5 Nit-6 Nit-7 Nit-8 F N = 20 N ; v = 0,3 m.s -1 F N = 100 N ; v = 0,3 m.s -1

21 Results Lubricated contact Wear (after 24h test) Page 21

22 Results Lubricated contact Interpretation Page 22 Initiation distance of lubricant film («running-in») surface accommodation faster for nitrocarburizing parts S carb < S Nit P carb > P Nit Eh Carb < Eh Nit real contact surface real contact pressure Thickness of lubricant film (Hamrock-Dowson) µ Carb < µ Nit W Carb > W Nit

23 Results Lubricated contact Interpretation Page 23 For nitrocarburized surfaces: Large influence of surfaces caracteristics (roughness and wettability) on «running-in capacity» Initiation distance of lubricant film (m)

24 N2M 2014 Carbonitriding & Nitrocarburizing Page 24 BEHAVIOURS IN DRY CONDITION

25 Results Dry contact Coefficient of friction evolution in dry condition Page 25 Unstable behaviour = scuffing Nit 2 Average of the post-oxyded nitrocarburizing

26 Results Dry contact Wear in dry condition Page 26 Good tenacity Low tenacity

27 Results Dry contact Wear track of plate x 500 Page 27 Carbonitrided plate Scuffing x x 70 Polishing action of the 3 rd body

28 Results Dry contact Wear track of plate Page 28 Nitrocarburized plate Presence of «pads» of iron oxyde on wear track of nitrocarburized plates

29 N2M 2014 Carbonitriding & Nitrocarburizing Page 29 CARBONITRIDING & NITROCARBURIZING CONCLUSIONS

30 Conclusions Dry contacts Page 30 Advantages of nitrocarburizing in comparison to carbonitriding: Improvement of the coefficient of friction from 20 to 40% Decrease of wear from 60 to 80 % Scuffing resistance Role of the compound layer? Beneficial influence of post-oxydation Fe 3 O 4 layer (iron oxyde pads?) Favourable role of γ nitrides

31 Conclusions Lubricated contacts Page 31 Advantages of nitrocarburizing in comparison to carbonitriding: Improvement of running-in capacity (initiation of lubricant film) Decrease of wear Role of the compound layer? Large influence of wettability and roughness of surfaces (what is the influence of the surface chemistry?)

32 THANK YOU FOR YOUR ATTENTION!!! Thank to Mr Cavalié (Hacer), Mr Chomer (Thermi Lyon), Mr Jacquot (Bodycote), Mr Villard (HEF) and Mr Warter (Metatherm) for their contribution to this study.