This document summarizes various surface treatment techniques including mechanical processes like shot peening and deep rolling that modify the surface without changing chemistry, thermal processes like electron beam treatment and laser treatment, and thermo-chemical processes like carburizing, nitriding, and carbonitriding that diffuse elements like carbon or nitrogen into the surface. It provides details on the mechanisms, advantages, and applications of these different surface modification methods.

1. Alexandria UniversityEngineering FacultyProduction Engineering Department3rd Year Production EngineeringAcademic Year 2008/2009

2. Surface Treatment Formation of Technological Surface Layers

3. NON-TRADITIONAL MACHINING BROJECT on surface treatmentBY: Abed El-Rahman Hefzy Amir El-Islam Mahmoud Mouneir Mohammed Saad Jahin Mohamed Samir Assem Reem Mamdouh Dalia Rashid Supervised by:- Prof: Hassan A. EL-Hofy 3 5/19/2009

4. Contents Introduction Surface Modification without Changing the Material Chemically Mechanical processes Thermal processes Surface Modification by Changing Surface Chemically Thermo-chemical Diffusion Processes Electrochemical Processes Chemical Conversion Coatings Surface Modification by Adding New Material onto the Surface (Coating) 5/19/2009 4

5. INTRODUCTION There’s 5 components for any machining process: Work piece Tool Machine tool Environment Process Variables 5/19/2009 5

6. They can cause High Temperature involved in the machining process Plastic deformation of the work material (Residual stress) Surface geometry (roughness, cracks, distortion) Chemical reactions, particularly between the tool and the work piece 5/19/2009 6

7. Surface engineering Refers to a wide range of technologies designed to modify the surface properties of metallic and non-metallic components for specific and sometimes unique engineering purposes. 5/19/2009 7

9. Improve wear resistance to extend useful component life

10. Improve the appearance of components to make them more visually attractive

11. Impart special properties such as lubricity enhancement, non-stick surfaces, etc

12. Apply adhesives that secure threaded fasteners in safety critical applications

13. Improve electrical conductivity

14. Improve solderability

15. Metallise plastic component surfaces

16. Provide shielding for electromagnetic and radio frequency radiation 5/19/2009 8

17. Surface engineering classifications Surface Modification without Changing the Material Chemically Surface Modification by Changing Surface Chemically Surface Modification by Adding New Material onto the Surface (Coating) 5/19/2009 9

18. 1-surface modification without changing the material chemically Processes that aims to treat the surface of the product without making any change in the chemical composition of it. they can be classified as: A- Mechanical Processes B- Thermal Processes 5/19/2009 10

19. A-Mechanical Techniques By : Abd El-Rahman Hefzy

20. A- mechanical processes The mechanical surface treatment is based on the elastic-plastic cold-working of the surface. The surface layers are work-hardened and residual compressive stresses are generated. The surface resistance against fatigue crack initiation and propagation, corrosion fatigue or friction fatigue increases significantly and therefore, improves the structural performance under cyclic loading. In addition to that, a reduced surface roughness due to the flattening of roughness peaks can be expected. 5/19/2009 12

21. Mechanical surface treatment techniques Peening Deep rolling Shot blasting 5/19/2009 13

22. Peening It is the process of working a metal's surface to improve its material properties by mechanical means such as hammer blows or by blasting with shot (shot peening). Peening is normally a cold work process (laser peening being a notable exception). It tends to expand the surface of the cold metal, thereby inducing compressive stresses or relieving tensile stresses already present. Peening can also encourage strain hardening of the surface metal. 5/19/2009 14

23. Peening cont’d Types of peening Shot peening. Laser shock peening (not mechanical process). Ultra sonic shot peening. 5/19/2009 15

24. shot peening 5/19/2009 16 The mostly used mechanical surface treatment method

25. Advantages of shot peening method Adjustability of the strengthening effect High processing quality Easy surface cleaning Being well established in the industry It enhances fatigue strength and durability of the material (as a general purpose for mechanical treatment) 5/19/2009 17

26. Disadvantages of shot peening method Bad surface quality 5/19/2009 18

27. Fatigue enhancement in an automobile spring using shot peening 5/19/2009 19

28. Laser shot peening (not mechanical method) 5/19/2009 20

29. Deep rolling 5/19/2009 21

30. Deep rolling cont’d 5/19/2009 22

31. Advantages of deep rolling method Great depth of the work hardening states and macroscopic compressive residual stresses 5/19/2009 23

32. Shot blasting Shot blasting consists of attacking the surface of a material with one of many types of shots. Normally this is done to remove something on the surface such as scale. The shot can be sand, small steel balls of various diameters, granules of silicon carbide, etc. The device that throws the shot is either a large air gun or spinning paddles which hurl the shot off their blades. 5/19/2009 24

33. 1-surface modification without changing the material chemically Processes that aims to treat the surface of the product without making any change in the chemical composition of it. they can be classified as: A- Mechanical Processes B- Thermal Processes 5/19/2009 25

34. B-Thermal Techniques By : Mohamed Samir Ahmed Assem Mohamed Sa3d Jaheen

35. Common High Energy Processes Electron Beam Treatment: Alters the surface properties by rapid heating — using electron beam and rapid cooling — in the order of 106 ºC/sec in a very shallow region, 100 µm (.004 in), near the surface. Ion Implantation: uses electron beam or plasma to impinge gas atoms to ions with sufficient energy, and embed these ions into atomic lattice of the substrate, accelerated by magnetic coils in a vacuum chamber. creates atomic defects that hardens the surface. Laser Beam Treatment: Similar to electron beam treatment, laser beam treatment alters the surface properties by rapid heating and rapid in a very shallow region near the surface. The results of high-energy processes are not well known or very well controlled. But the preliminary results look promising. Further development is needed in high-energy processes, especially in implant dosages and treatment methods. 5/19/2009 27

36. Electron Beam Technique By : Mohamed Samir Ahmed Assem

37. The process of EB Hardening. Uses high velocity concentrated beam of electrons as an energy source to selectively heat localized part of ferrous surfaces. EB techniques use extremely high energy input to austenitize a very thin surface layer in a fraction of a second. The bulk of the substrate remains cool and provides an adequate heat sink for "self-quenching". 5/19/2009 29

38. Hardening 5/19/2009 30

39. Mechanism of Interaction Accelerated electrons penetrate the surface of the treated material. As a result of this interaction, electric fields of these particles of crystalline lattice are disturbed, causing a rise in the amplitude of their vibration. This is manifest by a significant rise in temperature. The beam is manipulated using electromagnetic coils. needs to be performed under vacuum conditions since the electron beams dissipate easily in air. Speed : 400,000 Inch/s (10160 m/s). 5/19/2009 31

40. Self Quenching An important requirement for successful EB heat treatment is that the work piece mass must be sufficient to permit self-quenching of the heat-treated areas. A mass of up to eight times that of the volume to be hardened is required around and beneath the heated surfaces. 5/19/2009 32

41. Machines 5/19/2009 33

42. Electron beam machining Vs Electron beam surface treatment 5/19/2009 34

43. Electron beam machining Vs Electron beam surface treatment (cont.) EBM machines utilize voltages in the range of 50 to 200 kV to accelerate electrons to 200,000 km/s. Electromagnetic lenses are used to direct the electron beam, by means of deflection, into a vacuum. The electrons strike the top layer of the work piece, removing material, and then become trapped in some layer beneath the surface. EBM can be used for various material metallic and non-metallic although EB heat treatment works only on metallic materials 5/19/2009 35

44. Mirrored finishes 5/19/2009 36 Use Argon gas stored in the vacuum chamber to generate electron beam pulses. The un even surface is made flat by repeated fusion and coagulation resulting in a mirrored finish

45. Vacuum effect In vacuum In air 5/19/2009 37

46. Depth of penetration – Accelerating potential 5/19/2009 38

47. Energy-temperature-case depth 5/19/2009 39

48. Heating patterns 5/19/2009 40

49. . Focusing of the beam 5/19/2009 41

50. Advantages Shallow case-hardened depths (0.02 inch or less) Doesn’t disturb surface finish of the work piece. No surface oxidation due to vacuum. The surface can be hardened very precisely both in depth and in location. 5/19/2009 42

51. Limitations Requires vacuum. Work piece should be ferrous with sufficient amount of carbon. Interaction between material surface and the electron beam produces hazardous X-rays. Work piece size is limited to vacuum chamber size. Previously magnetized work pieces deflect the electron beam. A mass of up to eight times that of the volume to be hardened is required around and beneath the heated surfaces 5/19/2009 43

52. Surface Modification by Changing Surface Chemically Thermo-chemical Diffusion Processes. Electrochemical Processes. Chemical Conversion Coatings. 5/19/2009 44

53. Thermo-chemical techniques By: Amir El-Islam

54. Carburizing Carburizing is "thermo chemical" treatment, usually conducted at temperatures in the range 850-950°C in the first stage of "case-hardening". These processes change the chemical composition of the surface of a low-carbon steel component so that subsequent fast cooling, by "quenching" produces a hard "case" combined with a softer/tougher "core". Quenching is normally followed by a low-temperature tempering / stress relieving treatment. 5/19/2009 46 surface treatment project 2008/2009

55. Carburizing Methods 5/19/2009 47 surface treatment project 2008/2009

56. Pack Carburising the part that is to be carburized is packed in a steel container so that it’s completely surrounded by granules of charcoal. The charcoal is treated with an activating chemical such as Barium Carbonate that promotes the formation of Carbone Dioxide. CO2 reacts with the excess carbon in the charcoal to produce Carbon Monoxide CO reacts with the low-carbon steel surface to form atomic carbon which diffuses into the steel. 5/19/2009 48 surface treatment project 2008/2009

57. Gas Carburising Done with any carbonaceous gas, such as Methane, Ethane, Propane, or natural gas. Most carburizing gases are flammable and controls are needed to keep carburizing gas at 1700 ̊F from contacting air (Oxygen). Advantages Has an improved ability to quench from the carburizing temperature. Conveyor hearth furnaces make quenching in a controlled atmosphere possible. 5/19/2009 49 surface treatment project 2008/2009

58. Liquid Carburising It can be performed in internally or externally heated molten salt pots. Carburizing salt contains cyanide compounds such as sodium cyanide (NaCN). Cycle times for liquid cyaniding is much shorter (1 to 4 hours) than gas and pack carburizing processes. Disadvantages the disposal of salt. (environmental problems) and cost (safe disposal is very expensive). 5/19/2009 50 surface treatment project 2008/2009

59. Surface Characteristics Mechanical Properties Increased surface hardness Increased wear resistance Increased fatigue/ten Physical Properties Grain Growth may occur Change in volume may occur Chemical Properties Increased surface carbon content 5/19/2009 51 surface treatment project 2008/2009

60. In this process, nitrogen is diffused into the surface of the steel being treated. The reaction of nitrogen with the steel causes the formation of very hard iron and alloy nitrogen compounds. The resulting nitride case is harder than tool steels or carburized steels. The nitrogen source is usually Ammonia (NH3). At the nitriding temperature the ammonia dissociates into Nitrogen and Hydrogen. 2NH3 ---> 2N + 3H2 5/19/2009 52 surface treatment project 2008/2009 Nitriding

61. 5/19/2009 53 surface treatment project 2008/2009 Nitriding

62. Materials for nitriding steels include the SAE 4100, 4300, 5100, 6100, 8600, 8700, 9300 and 9800 series. some tool steels and certain cast irons. Advantages Hardness is achieved without the oil, water or air quench. Hardening is accomplished in a nitrogen atmosphere that prevents scaling and discoloration. Nitriding temperature is below the lower critical temperature of the steel and it is set between 925 ̊F and 1050 ̊F. 5/19/2009 54 surface treatment project 2008/2009 Nitriding

63. This process involves with the diffusion of both carbon and nitrogen into the steel surface. The process is performed in a gas atmosphere furnace using a carburizing gas such as propane or methane mixed with several percent (by volume) of ammonia. Methane or propane serve as the source of carbon, the ammonia serves as the source of nitrogen. Quenching is done in a gas which is not as severe as water quench. As a result of les severe quench, there is less distortion on the material to be treated. 5/19/2009 55 surface treatment project 2008/2009 Carbonitriding

64. Advantages it has a greater resistance to softening during tempering and increased fatigue and impact strength. This method is applied particularly to steels with low case hardenability, such as the seat of the valve. The process applied is initially carburizing to the required case depth (up to 2.5mm) at around 900-955°C, and then carbonitriding to achieve required carbonitrided case depth. The parts are then oil quenched, and the resulting part has a harder case than possibly achieved for carburization, and the addition of the carbonitrided layer increases the residual compressive stresses in the case such that the contact fatigue resistance and strength gradient are both increased. Applications Typical applications for case hardening are gear teeth, cams, Shafts, Bearings, fasteners, automotive clutch plates, tools, pins and dies 5/19/2009 56 surface treatment project 2008/2009 Carbonitriding

65. References: Surface Engineering of Metals Principles, Equipments and Technologies., tadeuszB. , CRC press 1999. Manufacturing engineering and technology , 5th edition , S. Kalpakjian, Prentice hall 2006 Web site http://surfaceengineer.co.uk/ on 13 may 2009. Website http://www.metallurgypdf.com/ on 13 may 2009. Robert H. Todd, Dell K. Allen and Leo Alting, Manufacturing Processes Reference Guide. Industrial Press Inc., 1994. pages 421-426 Oberg, E., Jones, F., and Ryffel, H. (1989) Machinery's Handbook 23rd Edition. New York: Industrial Press Inc. R. Chatterjee-Fischer - Wärmebehandlungv. E.: Nitrieren und Nitrocarburieren [Heat treatment of ferrous materials: nitriding and nitrocarburising] 1995 2nd Edition 5/19/2009 57

66. Thank YOU Hoping you have enjoyed the presentation 5/19/2009 58