Role of Surface Cracking and Recast
Layer Deposition on Formation
of Hardened Layer During EDM
of Inconel 825 with Varied Electrode
Material
Soni Kumari, Thrinadh Jadam, Gobinda Chandra Behera,
Santosh Kumar Sahu, Saurav Datta, Goutam Nandi, and Pradip Kumar
Abstract White layer or recast layer is considered one of the machining-induced
surface defects during electro-discharge machining (EDM). In the present work,
aspects of recast layer formation are studied during EDM of ‘difficult-to-cut’
aerospace superalloy Inconel 825. Effects of peak discharge current on the thickness
of the recast layer are studied in relation to different electrode materials used: Copper
and copper–nickel (90% Cu and 10% Ni). Formation of recast layer attributes to a
hardened layer, just beneath the machined surface. This is further verified through the
microhardness depth profile, which exhibits a strong dependence on recast layer
thickness. In addition, EDMed surface morphology is characterized by crack density,
which depends on peak discharge current as well as properties of tool electrode.
Keywords Recast layer · Electrical discharge machining (EDM) · Superalloy ·
Inconel 825 · Hardened layer · Microhardness · Crack density
1 Introduction
Inconel 825 is a nickel-iron-chromium (Ni–Fe–Cr)-based superalloy. This alloy
exhibits outstanding resistance when operated under corrosive as well as oxidationprone environments. This alloy finds wide application in various fields such as
nuclear, marine, aerospace and petrochemical industries. This is because of its excellent properties, especially at extreme temperatures. However, machining of nickelbased superalloys through conventional machining routes faces so many challenges
S. Kumari (B) · S. Datta · G. Nandi · P. Kumar
Department of Mechanical Engineering, Jadavpur University, Kolkata, West Bengal, India
e-mail: soni.1802@gmail.com
T. Jadam · G. C. Behera
Department of Mechanical Engineering, National Institute of Technology, Rourkela, Odisha, India
S. K. Sahu
Department of Mechanical Engineering, VSSUT Burla, Sambalpur, Odisha, India
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
A. K. Parwani et al. (eds.), Recent Advances in Mechanical Infrastructure,
Lecture Notes in Intelligent Transportation and Infrastructure,
https://doi.org/10.1007/978-981-33-4176-0_7
83
Layer Deposition on Formation
of Hardened Layer During EDM
of Inconel 825 with Varied Electrode
Material
Soni Kumari, Thrinadh Jadam, Gobinda Chandra Behera,
Santosh Kumar Sahu, Saurav Datta, Goutam Nandi, and Pradip Kumar
Abstract White layer or recast layer is considered one of the machining-induced
surface defects during electro-discharge machining (EDM). In the present work,
aspects of recast layer formation are studied during EDM of ‘difficult-to-cut’
aerospace superalloy Inconel 825. Effects of peak discharge current on the thickness
of the recast layer are studied in relation to different electrode materials used: Copper
and copper–nickel (90% Cu and 10% Ni). Formation of recast layer attributes to a
hardened layer, just beneath the machined surface. This is further verified through the
microhardness depth profile, which exhibits a strong dependence on recast layer
thickness. In addition, EDMed surface morphology is characterized by crack density,
which depends on peak discharge current as well as properties of tool electrode.
Keywords Recast layer · Electrical discharge machining (EDM) · Superalloy ·
Inconel 825 · Hardened layer · Microhardness · Crack density
1 Introduction
Inconel 825 is a nickel-iron-chromium (Ni–Fe–Cr)-based superalloy. This alloy
exhibits outstanding resistance when operated under corrosive as well as oxidationprone environments. This alloy finds wide application in various fields such as
nuclear, marine, aerospace and petrochemical industries. This is because of its excellent properties, especially at extreme temperatures. However, machining of nickelbased superalloys through conventional machining routes faces so many challenges
S. Kumari (B) · S. Datta · G. Nandi · P. Kumar
Department of Mechanical Engineering, Jadavpur University, Kolkata, West Bengal, India
e-mail: soni.1802@gmail.com
T. Jadam · G. C. Behera
Department of Mechanical Engineering, National Institute of Technology, Rourkela, Odisha, India
S. K. Sahu
Department of Mechanical Engineering, VSSUT Burla, Sambalpur, Odisha, India
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
A. K. Parwani et al. (eds.), Recent Advances in Mechanical Infrastructure,
Lecture Notes in Intelligent Transportation and Infrastructure,
https://doi.org/10.1007/978-981-33-4176-0_7
83