SURFACE ENGINEERING surfacing- Lect-2.pdf
- 1. Surface Engineering- Scope Failure of an engineering component occurs when its surface cannot adequately withstand the external forces or environment to which it is subjected. External forces can be thermal, optical, magnetic and electrical wear, or corrosion. Sometimes technological progress and manufacturing efficiency requires surface modifications. The economic benefits - According to a report the the UK coating market is approximately £21.3 b. (RSIC Report, 2005) Surface Characterization is perhaps the most powerful function which helps us the modify existing surfaces, create new coatings, formulations, understand mechanism of surface degradation and its improvement
- 2. Definition To make changes to the surface of a material. Purpose To gain or improve upon the desired surface properties of a material. To improve a components; performance, service lifetime, aesthetics or economics. Surface Engineering Processes There are many processes for modifying surface properties. These can be grouped into three categories
- 3. Surface Engineering Processes Surface modification without changing the material chemically Changes made by thermal or mechanical means, altering metallurgy or surface texture. Surface modification by altering surface chemistry These processes involve diffusion of new elements into the surface of the material. The original substrate material constituents play an active part in the modified surface. Surface modification by adding new material onto the surface (coating). These processes essentially add new material to the surface as a coating and do not involve the substrate material constituents at the surface.
- 4. Surface Modification without Changing the Material Chemically • Thermal Processes Surface Heat treatment, particularly those that undergo phase transformations like the martensitic reaction hardening of carbon steels, low alloy steels and cast irons - Laser, Flame, induction • Mechanical Processes Cold working - surface by peening, shot blasting, explosive hardening or other specialised machining processes induce compressive stresses, increasing hardness and fatigue resistance. • Changing surface texture using machining and blasting. • Other Processes Modification of surfaces by chemical/electro-etching, laser engraving, various chemical, solvent and ultrasonic cleaning processes could also be included here.
- 5. Surface Modification by Changing Surface Chemistry • Thermochemical Diffusion Processes – Carburising (carburizing) – carbonitriding – nitriding nitrocarburising – boronising • In all these processes new element goes into interstitial position. – aluminising (aluminizing, calorising, alonising) – chromising (chromizing) – siliconising (siliconizing) – In this process new element goes into Substitutional SS • Electrochemical Processes – Anodising (anodizing) of aluminium, titanium • Chemical Conversion Coatings – Phosphating chemical blacking chromating • Ion Implantation Processes
- 6. Surface Modification by Adding New Material onto the Surface (Coating) Welding Type Processes Thermal Spray Process Electroplating Electroless plating Galvanising, molten bath -tin aluminium (Al not aluminide) babbit PVD Physical Vapour Deposition CVD Chemical Vapour Deposition Painting Spin Coating Powder Coating Lubricants Tiling Cladding
- 8. Why Surface Treatment ? To achieve desired surface properties which cannot be achieved by conventional alloying process.
- 9. What are the surface Properties? Corrosion Oxidation Wear Erosion/abrasion Hardness Conductivity
- 10. What are the various modes by which surface properties can be enhanced ? Creating a Barrier Surface treatments
- 11. Different Techniques to achieve Surface Modifications Conventional Methods Advanced Methods
- 12. Selection of Surface Treatment Method Based upon Change in function property Substrate characteristics Thickness of the modified surface Throughput of the process ( slow, fast) Requirement of vacuum Geometry of the component Economics
- 13. Thickness as Selection Criteria for Coating Technique
- 14. Surface Engineering Gaseous State Solution Molten/semi molten •PVD •Ion Implantation •Ion Beam Assisted •CVD Sol-Gel Electroplating Laser Thermal Spray Welding
- 15. Classification of Coatings Types Of Coating Processes CVD PVD Thermal spray Mechanism of Coatings Mechanism of Coatings Mechanical Bonding Types Of Coating Diffusion Of Coating A B
- 16. Important parameters to be optimized to control the properties at substrate coating and its interface Substrate Interface Coating Coating Surface •Roughness •Erosion •Corrosion/oxidation •Friction •Porosity •Electrical properties Coating Bulk Cohesion Stress Adhesion Cracks/defects Graded composition Multilayers Interface Adhesion Interdiffusion Cleanliness Roughness Expansion mismatch
- 17. Surface Property Improvement Triangle Surface modification technique
- 18. Examples of Surface Modification in Industry S.No . Industry Part/machine Problem for which coating is required 1 Aircraft , Gas Turbine Turbine Disc, Lybrinth seals Turbine Blades Rotor Shafts Fretting wear Friction / Hot Corrosion Hot Corrosion and erosion Fretting wear 2 Automobiles Exhaust Nozzles Cylinder jackets and Liners Piston Heads and crowns Camshafts/Crank shafts High Temperature Corrosion Rubbing wear Thermal Fatigue and Corrosive wear Fatigue/wear 3 Textile Machinery Yankey Dryers Grooved rolls Package drive rolls Twisting rolls Yarn guides Tension gates & drives Abrasion and wear Abrasion and wear Abrasion and wear Abrasion and wear Abrasion and wear Abrasion and wear
- 19. 4 Glass Work Diamond Work Scoops and Moulds Dies Bushing Plates Diamond Polishing Pads Hot Corrosion/abrasion Hot Corrosion/abrasion Hot Corrosion/abrasion Abrasive Wear 5 Paper & Pulp Printing Industry Gripper Bars/pads Grip Rolls Transport Rolls Guide Plates Folder Rolls Abrasive wear Abrasive wear Abrasion Rubbing wear Surface wear 6 Chemical, Petrochemical Oil exploration Shafts Well Casing Tanks & Vessels Impellers Plug valves Abrasive wear Corrosive wear Corrosive wear Fatigue & Corr. Wear Chemical corrosion 7 Power Plants Boilers Gas Turbine Blades Furnace Pipes Superheater tubes Boiler Tubes Corrosion and abrasion Heat Corrosion Oxidation/sulfidation/erosion/Hot Corrosion Heat & sulfidation attack Coat Chuts Abrasive wear
- 20. Plasma & Ion-based Surface Engineering (PISE) techniques • Large surfaces are easily treatable • PISE is based on dry technology, avoiding the use of harmful solutions • unlike traditional techniques, the processes are virtually pollution free • such processes can be easily automated • properties such as corrosion and wear resistance, fatigue strength and biocompatibility, as well as the combination of these properties, are achievable and controllable
- 26. Mould locking plates Crankshafts Connecting rods Cam chain sprocket
- 28. 300- 1200