Sagar Sarkar

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Verified

Sagar verified their affiliation via an institutional email.

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• Ph.D
• Assistant Professor at Indian Institute of Technology Delhi

In today's era of modern manufacturing, selective laser melting is getting increasingly popular due to its capability of producing geometrically complex parts directly from CAD model in a single step. Few papers have reported the fatigue behaviour of selective laser sintered stainless steel specimens. In the present study, effect of tensile, zero a...

One of the most popular additive manufacturing processes is laser based direct metal laser sintering process which enables us to make complex three dimensional parts directly from CAD models. Due to layer by layer formation, parts built in this process tend to be anisotropic in nature. Suitable heat treatment can reduce this anisotropic behaviour b...

Laser surface hardening is a well-established process for enhancing the mechanical properties of selected surface areas of engineering parts made of different types of steel. Since this was first reported in the early seventies, much research has been done since to develop a deeper understanding of the process, process modeling for determining oper...

In this work, the effects of laser shock peening (LSP) on various 0properties of weld joints of AISI 304 stainless steel obtained by laser beam and electron beam welding are reported. Laser beam welding was carried out at speeds in 2.4–4.0 m/min range and 2 kW laser power. The effect of welding speed on the melt pool thermal characteristics and var...

Laser Beam Welding (LBW) has been carried out on precipitation-hardened 15-5 PH stainless steel. Different scanning speeds ranging from 2.4 m/min to 4.0 m/min with an interval of 0.4 m/min have been used for LBW at a laser power of around 2 kW to study the effect of weld-speed on melt-pool thermal properties, weld-microstructure, microhardness, and...

Article link: https://rdcu.be/dVKIZ In spite of having numerous applications in aerospace, automobile, and marine industries, Inconel 718 suffers from low surface hardness and wear resistance. In the present study, a novel method based on laser additive deposition has been proposed to address this drawback. Crack-free clad layer with much increase...

The discovery of metal additive manufacturing (MAM) has caused a significant revolution across multiple industries, enabling the production of prototypes and high-quality products with the added benefit of tailoring microstructural features in real time. This breakthrough has opened up new possibilities for the development of highly functional prod...

A hard and self-lubricious composite coating of tungsten disulfide (WS2) blended Inconel 625 alloy was deposited on AISI 304 stainless steel substrate by laser assisted cold spray (LACS) process through optimizing the laser power and gas pressure of the supersonic jet. Effects of the laser power which determined the deposition temperature and the g...

Nitrogen in austenitic stainless steel improves its strength through solid solution strengthening. Loss of nitrogen from the molten metal pool is a common phenomenon, and it is difficult to maintain the uniformity of nitrogen throughout the weld joint. Two grades of nitrogen containing steels (BS: 21-4N and 23-8N) with 0.39 and 0.28 wt% nitrogen wa...

Laser Assisted Cold Spray (LACS), a hybrid deposition process can be used to deposit crack free coatings in solid state with high compressive residual stress for variety of materials. However, high gas consumption rate, high maintenance cost, and costly experimental set-up often restricts its widespread usage in industries. The present work attempt...

The present article reports the fatigue crack growth (FCG) rate and fracture toughness of 15-5 Precipitation Hardening (PH) Stainless Steel (SS) specimens fabricated by Laser powder bed fusion (L-PBF) additive manufacturing (AM) technique. The effect of notch orientation (parallel and orthogonal in reference to build direction) on FCG and fracture...

The laser coating of NiCrBSi in pure form as well as with the addition of lubricious Ag or WS2 has been developed on Ti6Al4V substrate. With the help of an IR pyrometer, real-time thermal history was monitored and correlated with the tribological properties of the coating. A matrix predominantly comprised of NiTi and NiTi2 and reinforced with hard...

Friction stir welding (FSW) of CuCrZr sheets was performed and Laser Shock Peening (LSP) was carried out as a post-weld surface treatment. Effect of LSP on hardness, tensile and fatigue strength was investigated. Depth of compressive residual stress in base material increased from 550 µm to 700 µm when the number of LSP shots was increased from one...

In-situ laser deposition of Ni powder as an interlayer has been exploited to join dissimilar metals, titanium and stainless steel. Direct fusion joining of these materials often suffers from longitudinal cracks due to the formation of hard and brittle intermetallics of Ti and Fe, and also transverse cracks because of large difference in their therm...

Surface properties play a critical role in the structural integrity of any component and this becomes even more critical for weld joints. Laser shock peening (LSP) is one of the non-contact methods which is getting popular in industries to enhance surface properties for improving service life, mainly fatigue of engineering components. In the presen...

Laser powder bed fusion technique has been considered as one of the best metal additive manufacturing processes considering the part quality and dimensional accuracy. However, the high cost of metal powders makes it difficult to afford for all kinds of applications. Reusability of the powders can overcome this issue, but the effect on various mater...

Additive manufacturing (AM) has been widely considered as a popular manufacturing technique for the production of specific engineering components by various industries. Among the various AM techniques, laser powder bed fusion process (L-PBF) has the potential to make defect-free parts with good material properties. However, the mechanical propertie...

Laser cladding of Ni-based superalloys has been studied extensively in the recent past owing to their combined properties of high strength and corrosion resistance at elevated temperatures, due to which they are finding wide applications in gas turbine engines, land-based power-generation gas turbines, nuclear and fossil fuel power plants, etc. The...

In the present study laser beam welding of commercially pure titanium is carried out at different welding speeds. Effect of the addition of active flux layer of MgF2 on the morphology and geometry of the weld zone and surrounding regions is investigated along with its influence on the tensile strength of the welded joints. The active flux narrowed...

Deposition of ceramic-metal matrix composite using laser directed energy deposition process presents multi-fold challenges. High melting point ceramic particles often remain partially melted and increase the roughness of the deposit, which essentially requires secondary finishing operation. Besides high surface roughness, the high gradient of therm...

Layer by layer deposition in laser based metal additive manufacturing process causes accumulation of high thermal residual stresses. This may sometimes lead to dimensional inaccuracy and warping of the deposited clad layer. Additive manufacturing being expensive process, simulation may reduce the number of experimental trails. In the present work,...

In the present study, laser beam welding of commercially pure titanium has been carried out at different scan speeds in the range from 2.4 m/min to 4 m/min at 2.15 kW laser power and its influence on molten pool thermal history, microstructure, residual stress, mechanical and corrosion properties has been studied. Weld thermals cycles were monitore...

A novel method of monitoring cooling rates in real-time using two pyrometers arranged in tandem has been demonstrated. First pyrometer monitors the temperature at the center of the molten pool, second monitors the temperature at its tailing end. The difference in two pyrometer signals provides the temperature gradient at 1 kHz frequency from which...

Direct metal laser deposition of ceramic-metal composite coatings has received much attention in the recent past over other conventional methods due to a large number of advantages. However, formation of cracks due to large thermal gradients and rapid cooling rates limits its application. Therefore, in the present study the influence of cooling rat...

With recent advancements in additive manufacturing, Selective Laser Melting (SLM) is emerging as an unconventional manufacturing process of exceptional flexibility capable to fabricating any complex part without requiring expensive fixtures, tooling, mold or any other additional auxiliary with a very short lead time from design conceptualization to...

Additive Manufacturing (AM) is a method of joining metal/non-metals or composites layer by layer using different energy sources. Among the various AM processes, laser-based powder bed fusion (LPBF) is very popular, in which geometrically complex structures can be manufactured directly from CAD models. One of the least investigated areas in LPBF is...

Laser surface hardening of most of the industrial components require depth of surface modification in the range of 100-150 micron. Conventional laser surface hardening uses laser as a heat source to modify a particular area of the surface without melting in an inert gas environment. However, the hardened profile in this case shows peak hardness val...

Selective Laser Melting process enables production of geometrically complex parts directly from CAD model by melting metal powders layer by layer. For successful building of parts, some auxiliary structures namely support structures are also built to ensure proper heat conduction from actual parts to be built to the base plate. Support structures a...

One of the versatile additive manufacturing processes is laser based Selective Laser Melting (SLM) which allows to build complex intricate shapes directly from its three dimensional digital images. Layer by layer deposition and depending upon build orientations, SLM parts tends to be anisotropic in nature. Also non-uniformity in thermal loading acr...

One of the most popular additive manufacturing processes among today’s manufacturing industries is Selective Laser Melting (SLM) in which very intricate shapes can be fabricated directly from its three dimensional digital design data by melting metal powders using laser. Layer by layer deposition of material about different build axes make SLM part...

One of the most popular additive manufacturing processes is laser based direct metal laser sintering process which enables us to make complex three dimensional parts directly from CAD models. Due to layer by layer formation, parts built in this process tend to be anisotropic in nature. Suitable heat treatment can reduce this anisotropic behaviour b...

This article contains the glimpses of research works on laser materials processing carried out at the Laser Processing Laboratory at IIT Kharagpur under the guidance of Professor Ashish Kumar Nath during 2012 - 2016. This was published in the Bulletin of the Indian Laser Association, Kiran, Vol. 27, No. 3, December 2016.

An ergonomic study of manual material handling tasks in construction needs to address a number of manual material handling task-related problems such as pains in the back, shoulders and wrists, strain and sprain injuries, musculoskeletal disorders, severe fatigue and loss of energy of the workers and those acquired from improperly designed safety g...

From ergonomic point of view, work capability, efficiency, and performance of the workers may substantially decrease as they involve themselves in critical man-machine interactions during construction-related manual material handling tasks. Therefore, to improve the existing ergonomic performance of the work system as a whole with respect to a give...

This paper discusses the details of a study undertaken for biomechanical evaluation of a number of Manual Material Handling (MMH) tasks being carried out at a construction site in India. A comprehensive methodology involving a two dimensional dynamic biomechanical evaluation approach is developed for such construction MMH tasks involving carrying a...

Globalised supply chains, volatile energy and material prices, increased carbon regulations, competitive and marketing pressure for environmental sustainability are driving supply chain decision makers to reduce carbon emissions. Enterprises face the necessity and the challenge of implementing strategies to reduce their supply chain environmental i...