MINIMIZING POROSITY IN 17-4 PH STAINLESS STEEL COMPACTS IN A MODIFIED POWDER METALLURGICAL process

Utilize 17-4PH stainless steel (SS) powder with modified morphology and size in powder and sinter (P&S) technology to produce samples with significantly lower porosity compared to previous studies.

2. Powder Modification: Alter the shape of 17-4PH gas atomized
powder through ball milling.

3. Cold Pressing: Eliminate internal lubrication during cold pressing
and apply an extremely high compaction force.

4. Sintering Process: Utilize induction heating for rapid one-hour
sintering.

5. Investigate the effect of sintering temperature on porosity and mechanical
properties of the prepared samples.

1. MINIMIZING POROSITY IN 17-4 PH STAINLESS STEEL COMPACTS IN A MODIFIED POWDER METALLURGICAL PROCESS Presented By : NANDHAKUMAR N LKTE21ME079 Under the Guidance of : Prof. Arun MS Department of Mechanical Engineering Rajiv Gandhi Institute of Technology Kottayam August 2024 Department of Mechanical Engineering, RIT Kottayam 1

2. CONTENT INTRODUCTION MATERIALS AND METHODS EXPERIMENTAL PROCESS OVERVIEW POWDER CHARACTERIZATION MECHANICAL TESTING AND ITS PROPERTIES CONCLUSION Department of Mechanical Engineering, RIT Kottayam 2

3. INTRODUCTION Utilize 17-4PH stainless steel (SS) powder with modified morphology and size in powder and sinter (P&S) technology to produce samples with significantly lower porosity compared to previous studies. 2. Powder Modification: Alter the shape of 17-4PH gas atomized powder through ball milling. 3. Cold Pressing: Eliminate internal lubrication during cold pressing and apply an extremely high compaction force. 4. Sintering Process: Utilize induction heating for rapid one-hour sintering. 5. Investigate the effect of sintering temperature on porosity and mechanical properties of the prepared samples. Department of Mechanical Engineering, RIT Kottayam 3

4. OBJECTIVES 1. To utilize powder with slightly altered morphology and size in Powder Metallurgy and Sintering (P&S) technology to produce samples with significantly lower porosity compared to those produced by others. 2. To change the shape of 17-4PH gas atomized powder via ball milling. 3. To apply an extremely high compaction force. 4. To investigate the effect of sintering temperature on the porosity and the mechanical properties of the prepared samples. Department of Mechanical Engineering, RIT Kottayam 4

5. 17-4 PH STAINLESS STEEL 17-4 PH stainless steel, also known as UNS S17400 or 1.4542. A martensitic precipitation-hardening stainless steel. Widely used due to its high strength, hardness, and excellent corrosion resistance. Department of Mechanical Engineering, RIT Kottayam 5

6. Chromium (Cr): Approximately 15-17.5% Nickel (Ni): Approximately 3-5% Copper (Cu): Approximately 3-5% Manganese (Mn): Up to 1% Silicon (Si): Up to 1% Niobium (Nb) and Tantalum (Ta): Approximately 0.15-0.45% Carbon (C): Up to 0.07% Phosphorus (P): Up to 0.04% Sulfur (S): Up to 0.03% COMPOSITION Fig. Chemical compositions of 17-4 PH SS powder (wt.%) Department of Mechanical Engineering, RIT Kottayam 6

7. MECHANICAL PROPERTIES High Strength: Can achieve tensile strengths of around 1100-1300 MPa. Hardness: Can be heat-treated to achieve high levels of hardness. Toughness: Good toughness properties, making it suitable for various applications. Fig. Mechanical Properties of 17-4 PH Stainless Steel Department of Mechanical Engineering, RIT Kottayam 7

8. APPLICATIONS Used in aerospace, chemical, petrochemical, and food processing industries. Commonly used for components like gears, valves, fasteners, and high-strength fittings. Department of Mechanical Engineering, RIT Kottayam 8

9. ADVANTAGES AND LIMITATIONS ADVANTAGES Combines high strength and hardness with good corrosion resistance. Versatile in terms of its applications and performance in different environments. LIMITATIONS More expensive compared to some other stainless steels due to its alloying elements and specialized heat treatments. Requires precise control during heat treatment to achieve desired properties. Department of Mechanical Engineering, RIT Kottayam 9

10. MATERIALS AND METHODS Leading to reduced tensile strength and fatigue resistance. Corrosion Resistance Wear Resistance IMPORTANCE OF MINIMIZING POROSITY Department of Mechanical Engineering, RIT Kottayam 10

11. TESTING METHODS Fig. Flow chart of the utilized PM processing steps and testing methods. Department of Mechanical Engineering, RIT Kottayam 11

12. POWDER METALLURGY PROCESSING SPHERICAL POWDER Powders with particles that are nearly spherical in shape. Spherical particles ensure good flowability and high apparent density. Favorable for certain manufacturing methods like Metal Injection Molding (MIM) and Additive Manufacturing (AM). Department of Mechanical Engineering, RIT Kottayam 12

13. POWDER METALLURGY PROCESSING 2. MILLING A mechanical process used to reduce particle size or alter particle shape. Includes ball milling, which involves grinding powders in a rotating cylindrical container with grinding media. Department of Mechanical Engineering, RIT Kottayam 13

14. POWDER METALLURGY PROCESSING 3. SIEVING A method to separate particles based on size by passing them through screens or meshes. Ensures uniform particle size distribution, which is critical for consistent compaction and sintering in powder metallurgy. Department of Mechanical Engineering, RIT Kottayam 14

15. POWDER METALLURGY PROCESSING 4. COLD PRESSING A process where powder is compacted into a desired shape at room temperature under high pressure. To form a green compact with sufficient strength for handling before sintering. Department of Mechanical Engineering, RIT Kottayam 15

16. POWDER METALLURGY PROCESSING 5. SINTERING A heat treatment process that fuses powder particles together without melting them entirely. Typically involves heating the compacted powder to a temperature below its melting point, causing atomic diffusion and densification. Department of Mechanical Engineering, RIT Kottayam 16

17. 6. MACHINING The process of removing material from a workpiece to achieve the desired shape, size, and finish. Techniques: Includes turning, milling, drilling, and grinding. POWDER METALLURGY PROCESSING Department of Mechanical Engineering, RIT Kottayam 16

18. 7. HEAT TREATMENT A series of controlled heating and cooling processes used to alter the physical and mechanical properties of a material. Improves properties such as strength, hardness, and ductility, often through processes like annealing, quenching, and tempering. POWDER METALLURGY PROCESSING Department of Mechanical Engineering, RIT Kottayam 17

19. SCANNING ELECTRON MICROSCOPY SEM (Scanning Electron Microscopy) is used to analyze the microstructure and fracture surfaces of sintered 17-4PH stainless steel samples. Department of Mechanical Engineering, RIT Kottayam 18 Fig. SEM micrographs

20. SCANNING ELECTRON MICROSCOPY FINDINGS Department of Mechanical Engineering, RIT Kottayam 18 Microstructure Analysis SEM micrographs show the effect of different sintering temperatures on the microstructure . At 1200°C, the original boundaries of cold-compacted powder particles are still visible. Fracture Surface Analysis The SEM micrographs of fractured surfaces show that sintering temperature affects the fracture mode . At lower temperatures (1200°C and 1250°C ).

21. TYPES OF TESTING HARDNESS TEST The hardness of an alloy, including 17-4PH stainless steel (SS), is influenced by its composition, microstructure (grain size, type, and quantity of phases), and porosity. Reducing porosity from 7.4% to 3.2% increases hardness from 339 HV to 412 HV. Department of Mechanical Engineering, RIT Kottayam 19

22. TYPES OF TESTING 2. DENSITY TEST The density of green (unsintered) samples was determined using the dimensional method. The Archimedes method was used to calculate the density of sintered samples. A theoretical density of 7.75 g/cm³ was applied for calculating porosity Department of Mechanical Engineering, RIT Kottayam 20

23. TYPES OF TESTING 3. TENSILE TEST Tensile testing evaluates both the strength and deformability of the material. Porosity significantly reduces the strain properties of the material, emphasizing the importance of decreasing porosity. Department of Mechanical Engineering, RIT Kottayam 21

24. TYPES OF TESTING 4. CHARPY TEST Assess the material's behavior under impact-like stress. Toughness of porosity-free 17-4PH SS is mainly dependent on the heat-treated condition. Porosity acts as a stress concentrator, initiating cracks. Department of Mechanical Engineering, RIT Kottayam 22

25. The primary goal of using modified 17-4PH stainless steel powder in Powder and Sinter (P&S) technology to produce samples with significantly lower porosity was successfully achieved. CONCLUSION Department of Mechanical Engineering, RIT Kottayam 23

26. REFERENCES Kareem, Q.M.; Mikó, T.; Gergely, G.; Gácsi, Z. Compaction Behaviors of 17-4ph, 316l, and 1.4551 Stainless-Steels Powders by Cold Pressing Method. SSRN 2024, 23, 4827283. [CrossRef] Seerane, M.N.; Machaka, R. Metal injection moulding of 17-4PH stainless steel: Effects of porosity on the mechanical properties of the sintered products. Mater. Sci. Eng. 2019, 655, 012033. [CrossRef] Kovacs, S.E.; Miko, T.; Troiani, E.; Markatos, D.; Petho, D.; Gergely, G.; Varga, L.; Gacsi, Z. Additive Manufacturing of 17-4PH Alloy: Tailoring the Printing Orientation for Enhanced Aerospace Application Performance. Aerospace 2023, 10, 619. [CrossRef] Department of Mechanical Engineering, RIT Kottayam 24

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