PSI - Issue 60

346 Nagaraja Bhat Y V et al. / Procedia Structural Integrity 60 (2024) 345–354 Y V N Bhat, M A Davinci, A Kumar, N L Parthasarathi, S I S Raj, D Samataray, B.K. Sreedhar / StructuralIntegrity Procedia 00 (2019) 000– 000

Young’s modulus in ‘N/m 2 ’

E 2 R 1

R 2 Contact surface radius of disc in ‘m’  1 Poisson’s ratio of pin  2 Poisson’s ratio of Disc h

Contact surface (spherical tip) radius of pin in ‘m’

Wear depth of pin with elastic deformation in ‘m’ Change in height of pin due to elastic deformation in ‘m’

h e h w

Wear depth of pin in ‘m’

Hardness of material in ‘N/m 2 ’ Dimensionless wear coefficient Specific wear coefficient in ‘m Contact pressure in ‘N/m 2 ’

H K

3 /N-m’

K H

P

S  Coefficient of friction ∆ Small sliding distance 1. Introduction Sliding distance in ‘m’ K mh

3 /N-m’

Modified specific wear coefficient in ‘m

Refuelling is a basic need of any power plant. Refuelling activity in nuclear power plant needs special attention as it involves handling of radioactive isotopes in a very hostile environment. The choice of material therefore, is as important as the choice of mechanisms for the design of a fuel handling machine. Since the machine has several moving components, it is expected to undergo wear and tear during its service life. The wear and tear of the components not only reduces its service life but also leads to loss of efficiency of the machine. Keeping these factors in view, Colmonoy-5, a nickel base alloy has been considered for hard facing of stainless steel which is the base structural material of the fuel handling machine of Prototype Fast Breeder Reactor (PFBR). Colmonoy-5, though a suitable material for the application, requires a complicated deposition process. In addition to the complexity, the soundness of the deposits also depends on many factors such as the deposition technique, geometry of the parts and process parameters. Moreover, Colmonoy-5 deposits are prone to development of cracks. These challenges, associated with hard facing can be avoided by selecting a suitable material having adequate tribological properties as the structural material itself. 440C steel is one of the candidate materials for this application. This steel has been used commercially in high temperature rolling contact bearings. However, limited information on the tribological properties of this steel is available in open literature. This includes the study carried out by A. J. Silfka, (1993) on this steel in oxygen environment for various loads, speeds and temperatures. The objective of the study was to study the material for aerospace application. These results however cannot be used for direct application in PFBR’s machines as some of its parts operate in air while the other parts are exposed to argon environment. The present work aims to bridge this gap in the literature by evaluating the tribological properties of the steel in air environment. The tribological properties are characterized by parameters such as coefficient of friction and wear coefficient.

2. Testing

2.1. Material

Table 1. Chemical composition of SS 440C in wt.%

Element

C

Cr

Si

Mn

Ni

Mo

P

S

Fe

Wt.%

0.95-1.2

16-18

0-1

0-1

0-1

0-0.75

0-0.04

0-0.3

Balance