The presentation is about the surface modification techniques to enhance tool life in hot forging. It is research-oriented to give the reader a thorough knowledge about its applications in the actual industry environment.

1. Wednesday, June 16, 2021 Presenter: Sahil Dhiman 1
Presented by : Sahil Dhiman
Post-graduation candidate of Department of Mechanical Engineering (Production)
As a requirement for the course PPI313- Metal Forming

2. CONTENTS
Wednesday, June 16, 2021 Presenter: Sahil Dhiman 2
Sr. No. Slide title Slide Number
1 Why Forging is an important manufacturing process? 3
2 Explanation of hot forging and how it is different from cold forging 4
3 Failure mechanisms of hot forging tools/dies (HFTs) 5
4 Methods to improve the durability of HFTs 6-7
5 Effects of surface modification on die life 8-9
6 Conclusions 10
7 Acknowledgement 11

3. WHY FORGING?
Wednesday, June 16, 2021 Presenter: Sahil Dhiman 3
What are the common engineering
characteristics/ properties of the
shown components?
1. What can be the possible failure
methods of these components
during operation?
2. What are the possible
manufacturing techniques can be
used to bring these desired
characteristics to avoid failure?
Meshing gear
(Image courtesy of IndiaMart)
Crankshaft
(Image courtesy of IndiaMart)
Valves and seat
(Image courtesy of IndiaMart)
Lifting hook
(Image courtesy of IndiaMart)
Note: Images are not to scale

4. HOT FORGING
Wednesday, June 16, 2021 Presenter: Sahil Dhiman 4
• Hot forging is a metalworking process in which metals are
plastically deformed above their recrystallization
temperature, which allows the material to retain its deformed
shape as it cools.
• Hot forging is accomplished using hydraulic or pneumatic
hammers, presses, and other similar machinery that are used
to compress the heated metal into its desired part shape.
• This is most often achieved using a custom die. The dies
used in hot forging are custom-made to match the
customer’s part designs. Because hot metal is more flexible,
this process allows for more intricate shapes than cold
forging, making a vast array of part geometries possible.
Figure 1. A Forging die; Arrow
showing insert placement for an
intricate geometry [1].
[1] V. Leskovšek, B. Podgornik, and M. Jenko, “A PACVD duplex coating for hot-forging applications,” Wear, vol. 266, no. 3, pp. 453–460, 2019.

5. FAILURE MECHANISMS OF HOT FORGING DIES
Wednesday, June 16, 2021 Presenter: Sahil Dhiman 5
• Tool wear significantly reduces the quality of the forgings.
• This, in turn, affects the functionality of the final product resulting from the forgings.
Figure 2. The most frequent damage of forging tools (a) abrasive wear; (b) thermo-
mechanical cracking; (c) a grid of thermo-mechanical cracking and chipping of the
surface layer; (d) plastic deformation; (e) and (f) a fatigue crack [2].
[2] Z. Gronostajski et al., “Selected effective methods of increasing the durability of forging tools in hot forging processes,” Procedia Manuf., vol. 27, pp. 124–129, 2019.

6. METHODS TO IMPROVE DURABILITY OF DIES
Wednesday, June 16, 2021 Presenter: Sahil Dhiman 6
• Diagram showing different classifications of the available methods for the improvement of
tool durability.
Figure 3. Methods to improve the forging tools durability [3].
[3] Z. Gronostajski et al.“Influence of the application of a PN+CrN hybrid layer on improvement of the lifetime of hot forging tools,” Procedia Eng., vol. 207, pp. 514–519, 2017.
Area of
interest as
per the
current study

7. METHODS TO IMPROVE DURABILITY OF DIES
Wednesday, June 16, 2021 Presenter: Sahil Dhiman 7
• Hybrid surface modification techniques employing surface coating and surface treatments
Figure 4. (a) Surface modification technique schematic; (b) actual modified surface [4]; (c) PVD- Physical Vapour
Deposition schematic.
[4] Z. Gronostajski et al., “Analysis of wear mechanisms of hot forging tools protected with hybrid layers performed by nitriding and PVD coatings deposition,” Wear, vol. 420–421, pp. 269–280,
2019.
(a) (b)
(c)

8. EFFECT OF SURFACE MODIFICATION ON HFTs
Wednesday, June 16, 2021 Presenter: Sahil Dhiman 8
• Effect of hardness on HFT
after various hybrid surface
modification techniques.
Figure 5. Effect of hardness with
distance from the surface of HFT;
(a) [5], (b) [6], (c) [7], (d) [8]
[5] Z. Gronostajski et al. , “The failure mechanisms of hot
forging dies,” Mater. Sci. Eng. A, vol. 657, pp. 147–160,
2016.
[6] Z. Gronostajski et al., “Influence of the phase structure of
nitrides and properties of nitrided layers on the durability of
tools applied in hot forging processes,” J. Manuf. Process.,
vol. 52, pp. 247–262, 2020.
[7] J. Marashi et al., “An evaluation of H13 tool steel
deformation in hot forging conditions,” J. Mater. Process.
Technol., vol. 246, pp. 276–284, 2017.
[8] Z. Gronostajskiet al., “Influence of application of
GN+Cr/CrN hybrid layer on durability improvement of die
inserts used in hot forging process of wheel forging,”
Procedia Manuf., vol. 15, pp. 396–403, 2018.

9. EFFECT OF SURFACE MODIFICATION ON HFTs
Wednesday, June 16, 2021 Presenter: Sahil Dhiman 9
• Wear characteristics of surface treatment - N (nitriding)
Figure 6. Figure 5. Distribution of wear in PN and CrN surface modified tool after (a) 4000, (b) 13000
forgings [9], (c) evolution of micro-cracks on the surface of HFTs [10].
[9] Z. Gronostajski et al., “Influence of the application of a PN+CrN hybrid layer on improvement of the lifetime of hot forging tools,” Procedia Eng., vol. 207, pp. 514–519, 2017.
[10] M. Podgrajšek et al., “Failure analysis of forging die insert protected with diffusion layer and PVD coating,” Surf. Coatings Technol., vol. 276, pp. 521–528, 2015.

10. CONCLUSIONS
Wednesday, June 16, 2021 Presenter: Sahil Dhiman 10
• Different surface modification techniques were reviewed to enhance the life of HFTs. The
following conclusions were drawn after the comparison:
1. Hybrid treatment was found to be a promising technique to enhance the durability and life of
HFTs. But due to the economic aspects, the PVD and high end coating techniques are
suggested only for the precision application tools.
2. Strain difference due to the thermal gradient between two surfaces in contact was the root
cause of cracking in coating. It is crucial to find a compromise between the hardness of the
surface layer and the thermal fatigue resistance, which indirectly affects the value of the die's
abrasive wear.
3. The investigations proved that the best durability was achieved for tools covered with the
composite ‘nitrided layer/CrN coating’, for which the increase in durability was almost 90%.

11. 0.097mm
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ACKNOWLEDGEMENT
THANK YOU