Tribology of Steel

1. Tribological study of steel
CR 4102 – Tribology of Materials
Submitted by:
Somya Ranjan Patra
Roll : 118CR0135
Course mentor : Prof. Debasish Sarkar
Department Of Ceramic Engineering
National Institute of Technology, Rourkela

2. Introduction
• The key to success in the metal forming process and
even getting the desired shape is tribological behaviour
between the contacting surfaces of tool and workpiece
materials;
• however, this may not be enough due to the die's
existence, and the surface quality of the workpiece after
forming must also be considered. As a result, lubricants
are commonly employed in the metal forming process
to enhance the tribological characteristics between the
contacting surfaces of the workpiece and the forming
tools in order to decrease friction, wear, and forming
forces.
• However, because lubricants are harmful to the
environment, attempts are being made to eliminate or
reduce the use of lubricants in metal forming processes.

3. Cause of interest in Steel Tribology
• When metal is formed without lubricants, the work piece material
tends to transfer and attach to the forming tools, especially when
forming materials like aluminium, stainless steel, and high strength
steel (HSS), resulting in poor surface quality and severe tool wear.
• As a result, several studies are looking at applying surface engineering
approaches to overcome such issues.

4. Cold work tool steel
• Although cold forming stainless steel has significant adhesion issues
on cold work tool steel surfaces, applying a solid film on the forming
tool's surface tends to overcome the problem.
• However, previous research has revealed little about the wear
mechanism of cold work tool steel in relation to the sliding movement
of work piece materials in cold forming operations;
• Thus, research is also focused on this topic, particularly using PVD-
deposited films to improve the tribological efficiency of the metal
forming tool surface, which is one of the production costs. There are
several varieties of films available today, each of which may be used
with a variety of tool materials.

5. Materials and Methods
• Grade JIS-SKD11cold work tool steel or similar AISID2, which is
frequently used in the tool and die industry, was chosen as the
contacting material. It was hardened and covered with commercial
solid films of various sorts.
• Anticorrosion workpiece materials, such as 304 BA austenitic stainless
steel (Bright-Annealed: highly reflective finish achieved by cold rolling,
bright annealing, and temper rolling), are widely utilised in various
industries.
• Optical emission spectroscopy was used to study the chemical
makeup of both materials (OES). Tensile tests following ASTME8 were
used to determine the mechanical characteristics of stainless steel.

6. Tribological Test
• Pin-on-Disk by Anton Paar Pin-on-disk testing
according to ASTM G99-95a was utilised to investigate
the tribological behaviour of contacting surfaces
under dry circumstances using a tribometer with a
rotating movement.
• Sliding velocity was investigated at three levels: 50,
100, and 150 mm/s, which corresponds to the
velocity range in traditional sheet metal forming
processes (i.e., bending, deep drawing, and blanking),
as well as the pressure generated between the
contacting surfaces of the tool material and the
sheetmetal, which can be high at 1247 MPa,
especially with high strength materials.
• As a result, normal loads of 2, 5, and 8N were utilised
in the experiments, which correspond to contact
pressures of 807, 1095, and 1280MPa, respectively,
according to the Hertzian contact equation.

7. Film Coatings
• A commercial film was chosen to offer information to the industrial sector
after reviewing the sorts of solid films utilised for this test in prior research
data.
• All solid films were deposited using a physical vapour deposition (PVD)
coating procedure, which produces a smooth, thin layer of film ideal for
covering tool surfaces with dimensional tolerance after coating.
• Using an HITASHI TM-1000 scanning electron microscope, the thickness of
the film layer on the surface of the die material was measured from the
ball cross section (SEM). A HYSITRON Ti-Premier nano indenter with a
linearly rising 0–1000N normal load and 50nm normal displacement was
used to test the hardness of film coatings. At five separate sites on the
coating, indentations were produced.

8. Surface Characteristics of Hardened Balls
• The mating substance will adhere to the contacting surface of the ball
when the sliding velocity is increased. Additionally, raising the
pressure between the contact surfaces enhanced the intensity of the
adhesion.
• As the test distance rose and the strength of the adhesion increased
by discovering work piece material debris that clung to the ball
surface, the adhesion of the work piece material on the ball surface
began in conjunction with abrasive wear.
• The work piece material that was stuck to the ball surface during
relative movement might slip off the surface of the ball and reattach
to the material, which is an indeterminate shape.

9. Wear Characteristics of Hardened Tool Steel
• The quantity of material removed can be reduced by the mating
material's adherence to the ball surface. The ball will lose less
material, especially if there is extreme adhesion on the ball surface
during the sliding distance.
• When compared to hardened balls with abrasive wear or abrasive
wear mixed with adhesion, this results in a low specific wear rate. This
occurrence, however, results in poor contact surfaces and has a direct
impact on the adhesive wear of the work piece material.

10. Anti-adhesion Performance of Film Coatings
• The adhesion of one steel material to the surface of a hardened grade
tool material and the tool material covered with various forms of solid
film has indefinite features, making quantitative material transfer
prediction difficult.
• These findings back with prior research that found that different
types of solid films had different anti-adhesion properties.
• When compared to other types of solid films, the film performs better
at eliminating the issue of steel material transferring and clinging to
hardened forming tools.

11. Choosing a suitable solid film
• It is generally known that using a solid film coating to improve the
tribological efficiency of tool material increases the cost of manufacture.
• Because of the film's hardness, it can inhibit plastic deformation of the tool
material, resulting in reduced wear, particularly when utilised under high
contact pressure circumstances.
• The hardness of the film, on the other hand, does not impede work piece
material adherence to the tool surface, according to this investigation.
Work piece material adherence to the tool surface is one of the indications
used to determine tool life in sheet metal cold forming.
• As a result, tool designers must select a solid film that is appropriate for the
sort of mating material.

12. Intensity of Adhesion and Friction coefficient
• The adhesion behaviour of the work piece material is influenced by the
sliding velocity and contact pressure. The intensity of the adhesion
increased as both factors rose. The hardness of the film that is coated on
the tool material surface helps to avoid tool material wear, which is
especially important while operating under high contact pressure. The
hardness of the film coating, on the other hand, has little effect on the
effectiveness of preventing work piece adhesion.
• The adhesion behaviour on the tool material surface is related to the
friction coefficient between the contacting surfaces. If there is no adhesion,
the friction coefficient between the ball and work piece surfaces is in the
0.5–0.7 range under dry conditions, and when adhesion to the contact
surface occurs, the friction coefficient rises to 0.7–0.9.

14. Severity of Adhesion
• Because the work piece material that bonded prevents tool material
removal, the severity of adhesion on the tool material surface affects
the quantification of tool wear.
• As a result, the wear behaviour discovered in this study will have an
impact on the measurement of work piece material adhesion.

15. DLC film
• When compared to the other types of solid films investigated, DLC
film provides the most efficient protection against grade stainless
steel adhesion on the tool material's surface.
• Furthermore, utilising a hardened non-coated ball with a low
sliding velocity and low contact pressure is more successful than
using CrN, TiN, or TiCN-coated balls in preventing stainless steel
adhesion on the ball surface.

16. DLC film contd.

17. References
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Natchanun Angsuseranee , Bhadpiroon Watcharasresomroeng, Pracha Bunyawanichkul, and Siradej Chartniyom
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• T. Horiuchi, S. Yoshihara, and Y. Iriyama, “Dry deep drawability of A5052 aluminum alloy sheet with DLC-coating,” Wear,
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ceramics tools,” Surface and Coatings Technology, vol.177-178, pp. 582–590, 2004.