1. 1 Teaching Innovation - Entrepreneurial - Global The Centre for Technology enabled Teaching & Learning, N Y S S, India DTEL DTEL (Department for Technology Enhanced Learning)

2. DEPARTMENT OF MECHANICAL ENGINEERING III-SEMESTER ENGINEERING METALLURGY 2 CHAPTER NO.6 Non-destructive testings and Powder metallurgy

3. CHAPTER 5:- SYLLABUSDTEL Principles of hardness measurement, Hardness Test Brinell, Rockwell, Vicker 1 23 3 6 7 8 4 5 Non-destructive tests – Ultrasound Test Die Penetration Test, radiography test Powder metallurgy – Introduction metal powder & its production blending & mixing, compaction sintering, Hot Isostatic Pressing, Secondary processes Advantages, limitations & application of powder metallurgy

4. CHAPTER-1 COURSE OBJECTIVESDTEL To learn about different types of destructive and non destructive testing of metals. 1 To understand powder metallurgy technique and its application 2 4 The student will be able:

5. CHAPTER-1 COURSE OUTCOMESDTEL To Perform destructive and non destructive testing of metals to evaluate mechanical properties 1 To identify different processes involved in powder metallurgy technique 2 5 The student will be able to:

6. DTEL Material testing 6 LECTURE 1 Why are metals tested ? Ensure quality Test properties Prevent failure in use Make informed choices in using materials Factor of Safety is the ratio comparing the actual stress on a material and the safe useable stress.

7. DTEL Material testing 7 LECTURE 1 Two forms of testing Mechanical tests – the material may be physically tested to destruction. Will normally specify a value for properties such as strength, hardness, toughness,etc Non-destructive tests (NDT) – samples or finished articles are tested before being used.

8. LECTURE 1DTEL Destructive testing 8 8 Hardness testing machine The indenter is pressed into the metal Softer materials leave a deeper indentation

9. DTEL Hardness Test 9 LECTURE 1 Brinell hardness test Uses ball indentor. Cannot be used for thin materials. Ball may deform on very hard materials Surface area of indentation is measured.

10. DTEL Classification of cast iron 10 LECTURE 1 Vickers hardness test Uses square pyramid indentor. Accurate results. Measures length of diagonal on indentation. Hardness Test

11. DTEL Classification of cast iron 11 LECTURE 1 Rockwell hardness tests Gives direct reading. Rockwell B (ball) used for soft materials. Rockwell C (cone) uses diamond cone for hard materials. Flexible, quick and easy to use. Hardness Test

12. DTEL Non-Destructive Test 12 LECTURE 2 Why use NDT? Components are not destroyed Can test for internal flaws Useful for valuable components Can test components that are in use

13. DTEL structure impactors 13 LECTURE 2 Ultrasonic testing Ultrasonic Sound waves are bounced off the component and back to a receiver. If there is a change in the time taken for the wave to return this will show a flaw. This is similar to the operation of a sonar on a ship. Operation. 1.The ultrasonic probe sends the sound wave through the piece. 2.The sound wave bounces of the piece and returns. 3.The results are then placed on the display screen in the form of peaks. 4.Where the peaks fluctuate this will show a fault in the piece. Uses. This is generally used to find internal flaws in large forgings, castings and in weld inspections. Non-Destructive Test

14. DTEL structure impactors 14 LECTURE 2 Non-Destructive Test

15. DTEL structure impactors 15 LECTURE 3 Penetrant testing Used for surface flaws. The oil and chalk test is a traditional version of this type of testing. Coloured dyes are now used. Non-Destructive Test

16. DTEL structure impactors 16 LECTURE 3 Non-Destructive Test

17. DTEL 17 LECTURE 3 Radiography (X-ray) Testing 1.The x-ray are released by heating the cathode. 2.They are then accelerated by the D.C. current and directed onto the piece by the tungsten anode. 3.The x-rays then pass through the test piece onto an x-ray film which displays the results. 4.The x-rays cannot pass through the faults as easily making them visible on the x-ray film. Uses. This is a test generally used to find internal flaws in materials. It is used to check the quality of welds, for example, to find voids or cracks. Non-Destructive Test

18. DTEL 18 LECTURE 3 Non-Destructive Test

19. DTEL Powder Metallurgy 19 LECTURE 4 Definition of Powder Metallurgy Powder metallurgy may defined as, “the art and science of producing metal powders and utilizing them to make serviceable objects.” OR It may also be defined as “material processing technique used to consolidate particulate matter i.e. powders both metal and/or non-metals.”

20. DTEL Powder Metallurgy 20 LECTURE 4 Importance of P/M: The methods of powder metallurgy have permitted the attainment of compositions and properties not possible by the conventional methods of melting and casting. Powder metallurgy is an alternative, economically viable mass production method for structural components to very close tolerance. Powder metallurgy techniques produce some parts which can’t be made by any other method.

21. DTEL Powder Metallurgy 21 LECTURE 4 The process of P/M is the process of producing metallic parts from metallic powders of a single metal, of several metals or of a combination of metals and non-metals by applying pressure. The powders are mixed mechanically, compacted into a particular shape and then heated at elevated temperature below the melting point of the main constituent.

22. DTEL Powder Metallurgy 22 LECTURE 4 POWDER METALLURGY: Powder metallurgy is a forming and fabrication technique consisting of three major processing stages. First, the primary material is physically powdered, divided into many small individual particles. Next, the powder is injected into a mold or passed through a die to produce a weakly cohesive structure (via cold welding) very near the dimensions of the object ultimately to be manufactured. Finally, the end part is formed by applying pressure, high temperature, long setting times during which self-welding occurs.

23. DTEL Powder Metallurgy 23 LECTURE 4

24. DTEL Powder Metallurgy 24 LECTURE 5 Properties of powder metallurgy products are highly dependent on the characteristics of starting powders Some important properties and characteristics – Chemistry and purity – Particle size – Size distribution – Particle shape – Surface texture Useful in producing prealloyed powders – Each powder particle can have the desired alloy composition Powder Manufacture

25. DTEL Powder Metallurgy 25 LECTURE 5 The majority of commercial powder is produced by some form of melt atomization – Atomization is a process where liquid metal is fragmented into small droplets and then are cooled and atomization into particles Figure 18-2 Two methods for producing metal powders: (a) melt atomization and (b) atomization from a rotating consumable electrode. Powder Manufacture

26. DTEL Powder Metallurgy 26 LECTURE 5 Additional Methods of Powder Manufacture Methods – Chemical reduction of particulate compounds – Electrolytic deposition – Pulverization or grinding – Thermal decomposition of particulate hydrides – Precipitation from solution – Condensation of metal vapors Almost any metal or alloy can be converted into powder

27. DTEL Powder Metallurgy 27 LECTURE 5 Rapidly Solidified Powder (Microcrystalline and Amorphous) If the cooling rate of an atomized liquid is increased, ultra-fine or microcrystalline sized grains can form Some metals can solidify without becoming crystalline (called amorphous materials) Amorphous materials can have high strength, improved corrosion resistance, and reduced energy to induce and reverse magnetization

28. DTEL Powder Metallurgy 28 LECTURE 5 Powders should be evaluated for their suitability for further processing 1)Flow rate measures the ease with which powder can be fed and distributed into a die 2)Apparent density is the measure of a powder’s ability to fill available space without external pressure 3)Compressibility is the effectiveness of applied pressure 4)Green strength is used to describe the strength of the pressed powder after compacting, but before sintering Powder Testing and Evaluation

29. DTEL Powder Metallurgy 29 LECTURE 6 Powder Mixing and Blending The majority of powders are mixed with other powders, binders, and lubricants to achieve the desired characteristics in the finished product Sufficient diffusion must occur during sintering to ensure a uniform chemistry and structure Unique composites can be produced Blending or mixing operations can be done either wet or dry

30. DTEL 30 LECTURE 6 Compacting Loose powder is compacted and densified into a shape, known as green compact Most compacting is done with mechanical presses and rigid tools – Hydraulic and pneumatic presses are also used

31. DTEL 31 LECTURE 6 Figure 18-3 (Left) Typical press for the compacting of metal powders. A removable die set (right) allows the machine to be producing parts with one die set while another is being fitted to produce a second product. (Courtesy of Alfa Laval, Inc., Warminster, PA.)

32. DTEL 32 LECTURE 6 Compaction Sequence Powders do not flow like liquid, they simply compress until an equal and opposing force is created – This opposing force is created from a combination of (1) resistance by the bottom punch and (2) friction between the particles and die surface Figure 18-4 Typical compaction sequence for a single-level part, showing the functions of the feed shoe, die core rod, and upper and lower punches. Loose powder is shaded; compacted powder is solid black.

33. DTEL 33 LECTURE 6 Additional Considerations During Compacting When the pressure is applied by only one punch, the maximum density occurs right below the punch surface and decreases away from the punch For complex shapes, multiple punches should be used Figure 18-5 Compaction with a single moving punch, showing the resultant nonuniform density (shaded), highest where particle movement is the greatest. Figure 18-6 Density distribution obtained with a double- acting press and two moving punches. Note the increased uniformity compared to Figure 18-5. Thicker parts can be effectively compacted.

34. DTEL 34 LECTURE 6 Complex Compacting If an extremely complex shape is desired, the powder may be encapsulated in a flexible mold, which is then immersed in a pressurized gas or liquid – Process is known as isostatic compaction In warm compaction, the powder is heated prior to pressing The amount of lubricant can be increased in the powder to reduce friction Because particles tend to be abrasive, tool wear is a concern in powder forming

35. DTEL 35 LECTURE 7 Sintering In the sintering operation, the pressed-powder compacts are heated in a controlled atmosphere to right below the melting point Three stages of sintering – Burn-off (purge)- combusts any air and removes lubricants or binders that would interfere with good bonding – High-temperature- desired solid-state diffusion and bonding occurs – Cooling period- lowers the temperature of the products in a controlled atmosphere All three stages must be conducted in oxygen-free conditions of a vacuum or protective atmosphere.

36. DTEL 36 LECTURE 7 Hot-Isostatic Pressing Hot-isostatic pressing (HIP) combines powder compaction and sintering into a single operation – Gas-pressure squeezing at high temperatures Heated powders may need to be protected from harmful environments Products emerge at full density with uniform, isotropic properties Near-net shapes are possible The process is attractive for reactive or brittle materials, such as beryllium (Be), uranium (U), zirconium (Zr), and titanium (Ti).

37. DTEL 37 LECTURE 7 Hot-Isostatic Pressing HIP is use to  Densify existing parts  Heal internal porosity in casting  Seal internal cracks in a variety of products  Improve strength, toughness, fatigure resistance, and creep life. HIP is relative long, expensive and unattractive for high-volume production

38. DTEL 38 LECTURE 7 Secondary Operations Most powder metallurgy products are ready to use after the sintering process Some products may use secondary operation to provide enhanced precision, improved properties, or special characteristics Distortion may occur during nonuniform cool-down so the product may be repressed, coined, or sized to improve dimensional precision

39. DTEL 39 LECTURE 7 Secondary Operations If massive metal deformation takes place in the second pressing, the operation is known as P/M forging – Increases density and adds precision Infiltration and impregnation- oil or other liquid is forced into the porous network to offer lubrication over an extended product lifetime Metal infiltration fills in pores with other alloying elements that can improve properties P/M products can also be subjected to the conventional finishing operations: heat treatment, machining, and surface treatments

40. DTEL 40 LECTURE 8 Advantages of P/M Virtually unlimited choice of alloys, composites, and associated properties – Refractory materials are popular by this process Controlled porosity for self lubrication or filtration uses Can be very economical at large run sizes (100,000 parts) Long term reliability through close control of dimensions and physical properties Wide latitude of shape and design Very good material utilization

41. DTEL 41 LECTURE 8 Disadvantages of P/M Limited in size capability due to large forces Specialty machines Need to control the environment – corrosion concern Will not typically produce part as strong as wrought product. (Can repress items to overcome that) Cost of die – typical to that of forging, except that design can be more – specialty Less well known process

42. DTEL 42 LECTURE 8 Powder Metallurgy Products 1)Porous or permeable products such as bearings, filters, and pressure or flow regulators 2)Products of complex shapes that would require considerable machining when made by other processes 3)Products made from materials that are difficult to machine or materials with high melting points 4)Products where the combined properties of two or more metals are desired 5)Products where the P/M process produces clearly superior properties 6)Products where the P/M process offers economic advantage

43. DTEL 43 LECTURE 8 Motor Cycle Parts Vehicles Engine Parts For Electric Motors

44. DTEL 44 LECTURE 8 Thank you!