WO2022074443A1

WO2022074443A1 - A method of manufacturing a metallic component by additive manufacturing process and a system thereof

Info

Publication number: WO2022074443A1
Application number: PCT/IB2020/061309
Authority: WO
Inventors: S. Sundar Sriram
Original assignee: Sundram Fasteners Limited
Priority date: 2020-10-09
Filing date: 2020-12-01
Publication date: 2022-04-14

Abstract

A method of manufacturing a metallic component by an additive manufacturing process is disclosed. The method comprises of printing a plurality of layers (2a) on a work bed (3) sequentially to form a metallic component. Printing of each of the plurality of metallic layers (2a) comprises of initially spreading a layer of powdered alloy (2) on the work bed (3). Then, traversing an energy source (1) over the layer of powdered alloy (2) in a pre -defined path at a pre-defined speed for printing the metallic layer. Further, the printed metallic layer (2a) is reheated to a temperature less than melting temperature (Tm) of the powdered alloy (2). The printed metallic layer (2a) is further cooled. The reheating serves for heat treating the printed metallic layer (2a) wherein the heat treating relieves stress and structural defects in the printed metallic layer (2a).

Description

A METHOD OF MANUFACTURING A METALLIC COMPONENT BY ADDITIVE MANUFACTURING PROCESS AND A SYSTEM THEREOF TECHNICAL FIELD Present disclosure generally relates to the field of additive manufacturing. Particularly, but not exclusively, the present disclosure relates to three-dimensional printing of metallic components. Further embodiments of the present disclosure disclose a process and a system for minimizing or eliminating defects during 3D printing of the metallic components. BACKGROUND OF THE INVENTION Manufacturing of components has evolved over time. Conventional methods of manufacturing such as process of injection moulding, machining, forming etc. require mass production to even out the overhead cost of tooling, labour for assembly, and production. Further, creating complex mechanical constructions via traditional manufacturing requires precision and skills. Multiple parts are often manufactured separately and are further assembled to form assemblies and sub-assemblies. With advancements in technologies, methods such as 3D printing or additive manufacturing is becoming increasingly relevant in the field of manufacturing. 3D printing is the process of using a suitable equipment to produce a component, layer by layer. The component is printed by the equipment which is communicatively coupled to a computer. Additive manufacturing offers some unique advantages such as the cost of manufacturing of one item stays the same irrespective of the quantity. Consequently, manufacturing components of low quantity and increased shape complexity is significantly cheaper when compared to traditional manufacturing methods which require mass production to even out the overhead cost of tooling, labour for assembly, and production as mentioned above. Unlike conventional manufacturing methods where multiple parts are individually manufactured and are painstakingly assembled to manufacture a component with complex structures, additive manufacturing enables the creation of both and individual component as well as the entire assembly in a single manufacturing process. Further, conventional manufacturing methods such as molding, often require the use of extra materials to fill the mold. Sheet metal assembly processes involves taking a whole piece of sheet metal and cutting holes into it. In above such manufacturing methods, the raw material yield will be well below 100%. However, 3D printing is extremely resource efficient when compared with traditional production processes where complex shapes can be formed in a single manufacturing process with a very high raw material yield in the vicinity of 100%. The above-mentioned aspects make additive manufacturing, an extremely appealing method of manufacturing additive manufacturing is gaining traction in recent times. Generally, additive manufacturing of metallic components involves the steps of spreading a powdered alloy on a work bed. The powdered alloy is heated suitably at pre-determined geometric paths to bond the individual particles metallurgically thereby resulting in a metallic layer being “printed”. The powdered alloy is again spread on the printed metallic layer and another metallic layer is printed on top of the existing metallic layer. This process is continued till the desired shape and size of the component is achieved. The process of heating the powdered alloy to form a metallic layer and cooling the metallic layer occurs rapidly. The time frame in which the heating, melting, solidification and cooling occurs is within a second or a few milli-seconds. Subjecting the powdered alloy/metallic layer to such rapid thermal processes, causes rapid metallurgical phase changes in the printed metallic layers. Consequently, microstructural, and macro-structural defects may be created. Further, when another metallic layer is printed on top of the already printed metallic layer with blemishes, an article riddled with defects is developed. The defects and cracks may further propagate through the printed structure and may lead to the failure of the structure. Such defects often reduce the overall working life of the component. Further, microstructure of the rapidly solidified metal will consist of a mixture of amorphous phases and cast grain structure consisting of equiaxed grains and dendritic grains. In the event of metals which undergo martensitic transformations, the phases will be a mixture of cast grain structure, un-tempered martensite, and amorphous phase. Continuing the printing of a layer over an un-tempered martensitic layer or an amorphous layer will result in the layer having micro cracks as well as macro cracks amongst other defects. The present disclosure is directed to overcome one or more limitations stated above, or any other limitation associated with the prior arts. SUMMARY OF THE DISCLOSURE One or more shortcomings of the conventional process are overcome, and additional advantages are provided through the provision of the system as claimed in the present disclosure. Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure. In one non-limiting embodiment of the disclosure, a method of manufacturing a metallic component by an additive manufacturing process is disclosed. The method comprises of printing a plurality of layers on a work bed sequentially to form a metallic component. The printing of each of the plurality of metallic layers comprises of initially spreading a layer of powdered alloy on the work bed. An energy source is traversed over the layer of powdered alloy in a pre-defined path at a pre-defined speed for printing the metallic layer. Further, the printed metallic layer is reheated to a temperature less than melting temperature of the powdered alloy. The printed metallic layer is further cooled. The reheating serves for heat treating the printed metallic layer to relieve stress and correcting or eliminating structural defects in the printed metallic layer. In an embodiment of the disclosure, the temperature of the metallic layer during the heat treatment of the metallic layer ranges between the melting temperature of the powdered alloy and bed temperature of the work bed. In an embodiment of the disclosure, the heating of the printed metallic layer is carried out by traversing the energy source used for printing the metallic layer in the predetermined path. In an embodiment of the disclosure, the energy source for printing the metallic layer from the powdered alloy is a primary energy source and energy source for heating the printed metallic layer is a secondary energy source. In an embodiment of the disclosure, the primary energy source is a first laser, and the secondary energy source is a second laser. In an embodiment of the disclosure, the energy source is commutatively coupled to a controller and the operation of the energy source is controlled by the controller. In an embodiment of the disclosure, the heat treatment of the printed metallic layer is sequentially performed by the secondary energy source traversing the same path as the primary energy source after a pre-determined time delay for cooling the printed metallic layer. In an embodiment of the disclosure, the heat treatment of the printed metallic layer is performed before the temperature of the printed metallic layer reaches the bed temperature. In an embodiment of the disclosure, the printed metallic layer is heat treated multiple times before printing of next layer of the plurality of layers. In an embodiment of the disclosure, the diameter of the first laser source is greater than a particle diameter of the powdered alloy on the work bed. In an embodiment of the disclosure, the diameter of the second laser source is smaller than the diameter of the first laser source. In an embodiment of the disclosure, the manufactured metallic component is subjected to subsequent reheating. In another non-limiting embodiment of the disclosure, an additive manufacturing system for manufacturing a metallic component is disclosed. The system comprises of a work bed for accommodating powdered alloy. At least one energy source which is elevated from the work bed is provided and a controller is communicatively coupled with the energy source. The controller is configured to traverse the energy source over the powdered alloy in a pre-defined path at a pre-defined speed for printing a plurality of metallic layer. The printed metallic layer is further cooled. The controller further traverses the energy source over each of the plurality of printed metallic layer to heat treat the printed metallic layers. The printed metallic layer is heated to a temperature less than melting temperature of the powdered alloy and heat treating relieves stress and structural defects in the printed metallic layer. The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES The novel features and characteristic of the disclosure are set forth in the appended claims. The disclosure itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which: Fig.1 illustrates a schematic view of an additive manufacturing system, in accordance with an embodiment of the present disclosure. Fig. 2 is a flow chart indicating the process of manufacturing a metallic component, in accordance with an embodiment of the present disclosure. Fig.3 is a graphical representation of heating and cooling cycles of powdered alloy and metallic layer respectively, in accordance with an embodiment of the present disclosure. Fig.4 is a graphical representation of the heating and cooling cycles of Fig. 3 along with the re-heating and cooling of the metallic layer, in accordance with an embodiment of the present disclosure. Fig.5 illustrates the additive manufacturing system of Fig.1 with the second layer of powdered alloy on the printed metallic layer, in accordance with an embodiment of the present disclosure. Fig. 6a is a micrographic view of the printed metallic layer (2a), in accordance with an embodiment of the present disclosure. Fig. 6b is a micrographic view of the heat-treated metallic layer (2a), in accordance with an embodiment of the present disclosure. Figs 7a to 7e, show a magnified image of the surface of the metallic layer (2a) which is not subjected to heat treatment. Figs 8a and 8b, show a magnified image of the surface of the metallic layer (2a) which is subjected to heat treatment, in accordance with an embodiment of the present disclosure. Fig. 9 illustrates schematic view of the additive manufacturing system with a second laser source in addition to first laser source, in accordance with an embodiment of the present disclosure. Fig.10 is a graphical representation of the heating and cooling cycle from the first laser source and the re-heating and cooling from the second laser source, in accordance with an embodiment of the present disclosure. The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein. DETAILED DESCRIPTION The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other system for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the disclosure. The novel features which are believed to be characteristic of the disclosure, as to its organization, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure. In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described below. It should be understood, however that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure. The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a system that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such mechanism. In other words, one or more elements in the device or mechanism proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the mechanism. Embodiments of the present disclosure discloses a method of manufacturing a metallic component by an additive manufacturing process. Generally, in additive manufacturing processes, the time frame in which the heating, melting, solidification and cooling of powdered alloy occurs is within a second or a few milli-seconds. Such rapid thermal processes cause rapid metallurgical phase changes. Consequently, microstructural and macro structural defects are created. These defects and cracks rapidly solidify as the metallic layer solidifies during cooling. The defects and cracks may further propagate through the printed structure and may lead to the failure of the structure. Such defects and cracks often reduce the overall working life of the component. Accordingly, the present disclosure discloses a method of manufacturing a metallic component where each printed layer is heat treated. The method of manufacturing comprises of printing a plurality of layers of the metallic component on a work bed sequentially to form a metallic component. The printing of each of the plurality of metallic layers includes spreading a layer of powdered alloy on the work bed. Further, a primary energy source is traversed over the layer of powdered alloy in a pre-defined path at a pre-defined speed for printing the metallic layer. The printed metallic layer is reheated by the primary energy source to a temperature less than melting temperature of the powdered alloy and the printed metallic layer is cooled after being heated. The reheating serves the purpose of heat treating the printed metallic layer where, the heat treating relieves stress and structural defects in the printed metallic layer. The present disclosure also discloses an embodiment where a secondary energy source is used to heat treat the printed metallic layer. In the following description of the embodiments of the disclosure, reference is made to the accompanying figures that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense. Fig.1 illustrates an additive manufacturing system (100). The system includes a work bed (3) housed inside an airtight chamber [not shown]. A layer of powdered alloy (2) may be spread on the surface of the work bed (3). In an embodiment, a layer of a pure metallic powder may be spread on the work bed (3). The type of metallic powder spread on the component may depend on the type of component that is to be manufactured. The environment in which the component is used may also play an important role in the selection of suitable metallic powder that is to be spread on the work bed (3). In an embodiment, any known powdered alloys or any known metallic powders may be used. The powdered alloy (2) may be levelled in a uniform manner after being spread on the work bed (3). The powdered alloy (2) may be spread on the work bed (3) such that the packing density of the powder alloy (2) particles on the work bed (3) are between the apparent density and the tap density of the metal/alloy powder on the work bed (3). Typically, this density ranges between 20% to 50% of the theoretical density of the metal. Further, apart from the work bed (3), the airtight chamber may also comprise of a first laser source (1) coupled to a traversing unit [not shown]. The operation of the traversing unit may be controlled by a controller (23) and the traversing unit may be configured to guide or direct the first laser source (1) in a pre-defined path and at pre-defined speeds. The maximum diameter of the particles in the powdered alloy (2) is indicated as “D_pmax” and the diameter of the first laser source (1) is indicated as “D_L1”. Further, the powdered alloy (2) that is spread on the surface of the work bed (3) may be selected such that the diameter (D_L1) of the first laser source (1) is greater than or equal to the maximum diameter of the particles (D_pmax) of the powdered alloy (2). It is critical that the diameter (D_L1) of the first laser source (1) is greater than or equal to the maximum diameter of the particles (D_pmax), as the area on which the laser beam incidents will also be greater. The larger laser diameter will help prevent or minimize the localized melting tendency of the powdered alloy (2) when the laser encounters the powdered alloy (2). Fig.2 illustrates a flow chart indicating the process of manufacturing a metallic component and the Fig.3 is a graphical representation of the heating and cooling cycles of powdered alloy (2) and metallic layer (2a) respectively. The first step 200 involves filling the chamber with a protective gaseous atmosphere. The chamber may be filled with inert gases. The work bed (3) inside the chamber of the additive manufacturing system (100) is spread with the powdered alloy (2). The metallic powder (2) may be uniformly distributed on the work bed (3) and the packing density of the powder alloy (2) as mentioned above may range between 20% to 50% of the theoretical density of the metal. The above-mentioned range of packing density of the powdered alloy (2) on the work bed (3) becomes crucial in partial or complete melting of the particles in the powdered alloy (2) when the laser beam incidents on the powdered alloy (2). The second step 201 involves traversing of the first laser source (1) over the powdered alloy (2) on the work bed (3). The laser may traverse at a pre-determined speed and the laser transmitted onto the powdered alloy (2) encompasses the section of the solid that is to be printed. The power and the energy density from the first laser source (1) may be adjusted such that the laser beam heats the powdered alloy (2) to a melting temperature (T_m). The heat transmitted from the laser causes the particles of powdered alloy (2) in its field of influence to metallurgically bond with each other either through sintering or melting, thereby printing the metallic layer (2a). The printed metallic layer (2a) is seen from the Fig. 5. The melting temperature (T_m) may vary for different powdered alloys (2) and the melting temperature may accordingly be changed by the user based on the type of powdered alloy (2) that is used for manufacturing of the component. The first laser source (1) may be coupled to the traversing unit as mentioned above. The traversing unit may guide the first laser source (1) through a pre- defined path at pre-defined speed. The path of the first laser source (1) may usually be specified by numerically controlled coordinates, defined by the sectional geometry of the article that is printed. In an embodiment, the path of the first laser source (1) may be specified by any of the known methods/means in the art. Fig.3 indicates the heating and cooling curves with respect to temperature and time. The curve 4 illustrates the heating of the powdered alloy (2) from a bed temperature (T_b) to the melting temperature (T_m) of the powdered alloy (2). Further, once the powdered alloy (2) is heated to the melting temperature (T_m), the particles bond together and a metallic layer (2a) is formed. The printed metallic layer (2a) is further allowed to be cooled for a pre-determined time. The metallic layer (2a) is allowed to be cooled for a time period until the temperature of the metallic layer (2a) almost drops to the bed temperature (T_b). Further, Fig. 4 is a graphical representation of the heating and cooling cycles of Fig.3 along with the re-heating and cooling of the printed metallic layer (2a). With reference to the Fig.2, the final step of heat treating the printed metallic layer (2a) is explained below. The process of heating the powdered alloy (2) to form a metallic layer (2a) and further cooling the printed metallic layer (2a) is already illustrated above. As seen from Fig.4, once the printed metallic layer (2a) is cooled as indicated by the curve 5, the metallic layer (2a) may further be subjected to heat treatment. The first laser source (1) may traverse over the printed metallic layer (2a) again in the same path as the first laser source (1) traverses over the powdered alloy (2) for printing the metallic layer (2a). The printed metallic layer (2a) may be reheated by the first laser source (1) before the temperature of the printed metallic layer reaches the bed temperature (T_b). The metallic layer (2a) may be reheated by the first laser source (1) to a first reheating temperature (T_r1) as indicated by the curve 8. This process of reheating the metallic layer (2a) causes the cracks and the defects inside the printed metallic layer (2a) to be relieved. Once, the metallic layer (2a) is heated to the first reheating temperature (T_r1), the metallic layer (2a) may be allowed to be cooled for a pre-determined amount of time as indicated by the curve 9. The cooling time may extend till the temperature of the metallic layer (2a) almost reaches the bed temperature (Tb). The first reheating temperature (T_r1) may range between the melting temperature (T_m) of the powdered alloy (2) and the bed temperature (T_b). The metallic layer (2a) may be reheated again to second reheating temperature (Tr2) for further relieving the cracks and the defects as indicated by the curve 10. The second reheating temperature (T_r2) may also range between the melting temperature (T_m) of the powdered alloy (2) and the bed temperature (T_b). The power and the energy density of the laser beam from the first laser source (1) may be reduced so that the reheating temperatures (T_r1 and T_r2) are lower than the melting temperature (T_m) of the powdered alloy (2). Once, the metallic layer (2a) is reheated to the second reheating temperature (T_r2), the metallic layer is cooled as indicated in the curve 11. The metallic layer (2a) may be further reheated multiple times as. The metallic layer (2a) may be reheated any number of times as required by the user until the cracks and the defects in the metallic layer (2a) are completely relieved. In an embodiment, the above mentioned parameters of energy density of the laser beam, power of the laser beam, thickness of the powdered alloy (2) on the work bed (3) etc. may vary with the change in type of powdered alloy (2) that is used on the work bed (3). Now referring to Fig.5, it illustrates the additive manufacturing system (100) of Fig.1 with a second layer of powdered alloy (2) on the printed metallic layer (2a). When the printed metallic layer (2a) is heat treated, the above-mentioned steps 200, 201 and 202 may be repeated. The second layer of powdered alloy (2) may be spread on top of the printed metallic layer (2a) and the first laser source (1) may be configured to traverse over the second layer of the powdered alloy (2) in a pre-defined path to print a new metallic layer on the existing metallic layer (2a). The newly printed metallic layer may also be reheated, or heat-treated multiple times. The subsequent layer below the newly printed metallic layer may also be heat treated when the newly printed metallic layer is subjected to heat treatment. The above-mentioned steps of spreading the powdered alloy (2), traversing a first laser source (1) over the powdered alloy (2) and heat treating the printed metallic layer (2a) may be repeated till the desired component is manufactured. Thus, heat treating each and every layer that is printed and relieving cracks or defects in each of the printed layers will improve the overall operational life of the manufactured component. Example: Further embodiments of the present disclosure will be now described with an example of a particular composition of the powdered alloy (2). The powdered alloy (2) used in this particular example may be high carbon steel. The particulars of this experiment are provided in the below table 1 and the corresponding results are provided in the table 1a.

Table.1

T^able.1a The first column of the table 1 indicates the parameters that the powdered high carbon steel (2) (sample 1) is subjected to when it is printed as the metallic layer (2a) on the work bed (3). The powdered high carbon steel (2) may be spread on the work bed (3) and the thickness of the powdered high carbon steel (2) on the work bed (3) may be of 30μ size. Further, the atmospheric pressure inside the chamber may be around 0.4 millibar. Once the powdered high carbon steel (2) is spread on the work bed (3), the laser may traverse at a speed of “Y” mm/second and the laser transmitted onto the powdered alloy (2) encompasses the section of the solid that is to be printed. The laser speed (Y) may range from 150 mm/second to 400 mm/second. As the first laser source (1) traverses over the powdered high carbon steel (2), the powdered high carbon steel (2) may be heated to its melting temperature (T_m). The power and the energy density of the laser beam may be around ”X” Watts and “Z” Joules/mm³. The power (X) of the laser beam may range from 40 to 175 Watts and the energy density of the laser beam may range from 200 to 400 j/mm³ which causes the particles of the powdered high carbon steel (2) to melt and bond together. Consequently, a metallic layer (2a) is printed on the work bed (3) and the thickness of the printed metallic layer (2a) may be around 50μ. With further reference to the table 1a, a Vickers hardness test was performed on the printed metallic layer (2a) and the through multiple tests, the average hardness of the printed metallic layer (2a) was found to be around 443 HV. The Fig.6a shows a magnified view of the printed metallic layer’s (2) surface. It is clearly observed from the Fig.6a that the surface of metallic layer (2a) is un- tempered, and the surface is riddled with defects. With further, reference to Figs 7a to 7e, which show a magnified image of the surface of the metallic layer (2a) which is not subjected to heat treatment. It is evident that the surface of the metallic layer (2a) is riddled with cracks and surface defects. Fig.7a and 7b show the image of metallic layer’s (2) surface with a magnification of 100μm and 10μm, respectively. The Figs. 7a to 7e are magnified images of the sample number 1, which is not subjected to heat treatment. From the Figs. 7a and 7b, it is clearly observed that the surface of the metallic layer (2a) is riddled with crater like features which are often formed due to the melting and rapid re- solidification of the powdered high carbon steel (2). These crater-like features invariably have defects and large cracks which propagate through the metallic component when the metallic component is subjected to various loads and will eventually lead to the premature failure of the metallic component. Figs. 7c to 7e further depict the magnified images of the defects on the surface of the metallic layer (2a) which was not subjected to heat treatment. With reference to the table 1, the second column indicates the parameters of the sample 2, where the printed metallic layer (2a) is suitably heat treated. The powdered high carbon steel (2) may be converted to a metallic layer (2a) as disclosed in the above-mentioned process. The metallic layer (2a) may be allowed to be cooled. The cooling time is chosen such that the temperature of the metallic layer (2a) reduces significantly, but the temperature does not reach the bed temperature (T_b). The printed metallic layer (2a) may be cooled such that the temperature of the printed metallic layer (2a) ranges between 300 degree Celsius to the melting temperature (T_m) of the high carbon steel (2). Once, the metallic layer (2a) is cooled, the first laser source (1) which is coupled to the controller (23) may be configured to traverse over the metallic layer (2a) before the metallic layer (2a) reaches the bed temperature (T_m). The first laser source (1) may traverse over the printed metallic layer (2a) again in the same path as the first laser source (1) traverses over the powdered alloy (2) for printing the metallic layer (2a). The first laser source (1) may traverse over the printed metallic layer (2a) at a speed which is equal to or greater than the speed (Y) of the laser traversing over the powdered alloy (2). In an embodiment, the speed (Y) of the laser traversing over the printed metallic layer (2a) may range from the speed (Y) of the laser traversing over the powdered alloy (2) to twice the speed (Y) of the laser traversing over the powdered alloy (2) (i.e. Y to 2Y). t. As the first laser source (1) traverses over the metallic layer (2a), the laser beam reheats the metallic layer (2a) to a first reheating temperature (T_r1). The power and the energy density of the laser beam from the first laser source (1) may be reduced. The power (X) of the laser may range from 0.25 times the power (X) of the laser traversing over the powdered alloy (2) to the normal power (X) of the laser traversing over the powdered alloy (2) (i.e.0.25X to 1X). Further, the energy density (Z) of the laser while re-heating the printed metallic layer (2a), may range from 0.15 times the energy density (0.15Z) of the laser traversing over the powdered alloy (2) to 0.6 times the energy density (0.6Z) of the laser traversing over the powdered alloy (2) (i.e. 0.15Z to 0.6Z). Thus, the reheating temperature (T_r1) is lower than the melting temperature (T_m) of the powdered alloy (2). This process of reheating the metallic layer (2a) causes the cracks and the defects inside the printed metallic layer (2a) to be relieved. With further reference to the table 1a, a Vickers hardness test is performed on the heat-treated metallic layer (2a) and the through multiple tests, the average hardness of the printed metallic layer (2a) was found to be around 361 HV. Consequently, it may be observed that the hardness of the heat-treated metallic layer (361 HV) is lesser than the hardness of the metallic layer (2a) which was only printed and not heat treated (443 HV). It may be therefore concluded that the heat treatment of the metallic layer (2a) reduces the hardness of the metallic layer (2a) and makes the metallic layer (2a) less brittle in nature. Consequently, the formation and propagation and cracks in the heat-treated metallic layer (2a) is significantly reduced and the overall operational life of the component may thereby be improved drastically. Fig. 6b shows a magnified view of the heat-treated metallic layer’s (2) surface. It is clearly observed from the Fig. 6b that the surface of metallic layer (2a) is more tempered, and defects observed are almost negligible. Figs 8a and 8b, show a magnified image of the surface of the metallic layer (2a) which is subjected to heat treatment. As clearly seen from the Figs. 8a and 8b, there are no crater like features on the surface of the metallic layer (2a) and reheating the printed metallic layer (2a) results in a tempered martensitic microstructure of the high carbon steel with very little or no cracks. Further, multiple experiments were performed on the powdered high carbon steel (2) and the parameters for processing the powdered high carbon steel (2) to print a metallic layer (2a),corresponding exemplary values are provided below in the table 2 and the table 3.

Table.2

Table.3 The above table 3, depicts the various operational parameters with tempering as the preferred method of heat treatment. Tempering is the process where the printed metallic layer (2a) is re- heated to a temperature below the melting point of the powdered high carbon steel (2). The metallic layer (2a) is then cooled in air. This process has the effect of strengthening the metallic layer (2a) by reducing brittleness and reducing internal stresses in the metallic layer (2a). Although the above table indicates the method of heat treatment as tempering, any other method known in the art may also be used for heat treating the metallic layer (2a). Referring now to Fig.9 which illustrates an embodiment of the additive manufacturing system (100) with a second laser source (17). Further, Fig. 10 is a graphical representation of the heating and cooling cycles from the first laser source (1) and the re-heating and cooling from the second laser source (17). The second laser source (17) here, may specifically be used for heat treating the printed metallic layer (2a) and the first laser source (1) may specifically be used for printing the metallic layer (2a) from the powdered alloy (2). Similar to the above- mentioned steps, a layer of powdered alloy (2) may initially be spread over the work bed (3). Further, the first laser source (1) may initially traverse over the powdered alloy (2) in a pre- defined path and at pre-defined speed. The first laser source (1) may heat the particles of powdered alloy (2) to a melting temperature (T_m) as indicated by the curve 18 of the Fig. 10. The heating of the powdered alloy (2) causes the particles of the powdered alloy (2) to bond together and thereby form a metallic layer (2a). The first laser source (1) after traversing over the powdered alloy (2) to print the metallic layer (2a) may be followed by the second laser source (17) with a pre-determined time delay. The second laser source (17) is used for the heat treatment of the printed metallic layer (2a). The time delay between traversing of the first laser source (1) and the second laser source (17) allows the printed metallic layer (2a) to be partially cooled before being reheated by the second laser source (17). The time delay is such that the metallic layer (2a) is partially cooled, and the second laser source (17) reheats the printed metallic layer (2a) before the metallic layer (2a) reaches the bed temperature (T_b). The cooling and the re-heating of the metallic layer (2a) are indicated by the curves 19 and 21, respectively. The second laser source (17) which reheats the metallic layer (2a) may traverse the same path as the first laser source (1) only with a suitable time delay. The second laser source may have a diameter DL2 and the diameter of the second laser source (DL2) is smaller than the diameter of the first laser source (D_L1). The first and the second laser source (1 and 2) may traverse in the direction “X” as indicated in the Fig.9. The metallic layer (2a) may be heat treated to the first reheating temperature (T_r1) which may range between the melting temperature (T_m) of the powdered alloy (2) and the bed temperature (T_b). The heat-treated metallic layer (2a) may further be allowed to cool as indicated by the curve 22. Further, the second laser source (17) may traverse multiple times over the metallic layer (2a), thereby repeatedly heat treating the metallic layer (2a). In an embodiment of the disclosure, the first laser source (1) and the second laser source (17) may be any suitable energy sources which are known in the art. The first laser source (1) may be referred to as a primary energy source and the second laser source (17) may be referred to as a secondary energy source. In an embodiment of the disclosure, the process of heat treating each of the plurality of metallic layers (2a) avoids the formation and propagation of cracks or defects in the component. Consequently, the overall operational life of the component is drastically improved. In an embodiment of the disclosure, employing a first laser source (1) for particularly printing the metallic layer (2a) and employing the second laser source for (17) for particularly heat treating the printed metallic layer (2a) allows the operational time in printing an heat treating the metallic layer (2a) to be considerably reduced. Equivalents With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. It will be understood by those within the art that, in general, terms used herein, are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding the description may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B." While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated in the description. Referral Numerals:

Claims

We Claim: 1. A method of manufacturing a metallic component by an additive manufacturing process, the method comprising: printing a plurality of layers (2a) on a work bed sequentially to form a metallic component, wherein, the printing of each of the plurality of metallic layers (2a) comprises: spreading a layer of powdered alloy (2) on the work bed (3); traversing an energy source (1) over the layer of powdered alloy (2) in a pre-defined path at a pre-defined speed for printing the metallic layer; and reheating the printed metallic layer (2a) to a temperature less than melting temperature (T_m) of the powdered alloy (2) and cooling the printed metallic layer (2a), wherein the reheating serves for heat treating the printed metallic layer (2a) to relieve stress and structural defects in the printed metallic layer (2a).

2. The method as claimed in claim 1, wherein the temperature of the metallic layer (2a) during the heat treatment of the metallic layer (2a) ranges between the melting temperature (T_m) of the powdered alloy and bed temperature (T_b) of the work bed (3).

3. The method as claimed in claim 1, wherein the heating of the printed metallic layer (2a) is carried out by traversing the energy source (1) used for printing the metallic layer (2a) in the predetermined path.

4. The method as claimed in claim 1, wherein the energy source (1) for printing the metallic layer form the powdered alloy (2) is a primary energy source (1) and the energy source for heating the printed metallic layer (2a) is a secondary energy source (17).

5. The method as claimed in claim 1, wherein the primary energy source (1) is a first laser source, and the secondary energy source (17) is a second laser source.

6. The method as claimed in claim 1, wherein the energy source (1) is communicatively coupled to a controller (23) and operation of the energy source (1) is controlled by the controller (23).

7. The method as claimed in claim 1, wherein the heat treatment of the printed metallic layer (2a) is sequentially performed by the secondary energy source (17) traversing the same path as the primary energy source (1) after a pre-determined time delay for cooling the printed metallic layer (2a).

8. The method as claimed in claim 1, wherein the heat treatment of the printed metallic layer (2a) is performed before the temperature of the printed metallic layer (2a) reaches the bed temperature (T_b).

9. The method as claimed in claim 1, wherein the printed metallic layer (2a) is heat treated multiple times before printing of next layer of the plurality of layers.

10. The method as claimed in claim 1, wherein diameter (D_L1) of the first laser source (1) is greater than a particle diameter (D_pmax) of the powdered alloy (2) on the work bed (3).

11. The method as claimed in claim 1, wherein the diameter (DL2) of the second laser source (17) is smaller than the diameter (D_L1) of the first laser source (1).

12. The method as claimed in claim 1, wherein the manufactured metallic component is subjected to subsequent reheating.

13. An additive manufacturing system for manufacturing a metallic component, the system comprising: a work bed (3) for accommodating powdered alloy (2); at least one energy source (1 and 17) elevated from the work bed (3); a controller (23) communicatively coupled with the energy source (1), wherein the controller (23) is configured to: traverse the energy source (1) over the powdered alloy (2) in a pre- defined path at a pre-defined speed for printing a plurality of metallic layer (2a) and cooling the printed metallic layer (2a); traverse the energy source (1) over each of the plurality of printed metallic layer (2a) to heat treat the printed metallic layer (2a); wherein, the printed metallic layer (2a) is heated to a temperature less than melting temperature (T_m) of the powdered alloy (2) and heat treating relieves stress and structural defects in the printed metallic layer (2a).

14. The system as claimed in claim 13, wherein the heating of the printed metallic layer (2a) is carried out by traversing the energy source (1) used for printing the metallic layer (2a) in the predetermined path.

15. The system as claimed in claim 13, wherein the temperature of the metallic layer (2a) during heat treatment of the metallic layer (2a) ranges between the melting temperature (T_m) of the powdered alloy and the bed temperature (T_b) of the work bed (3).

16. The system as claimed in claim 13, wherein the energy source for printing the metallic layer form the powdered alloy (2) is a primary energy source (1) and the energy source for heating of the printed metallic layer (2a) is a secondary energy source (17).

17. The system as claimed in claim 13, wherein the primary energy source (1) is a first laser source, and the secondary energy source (17) is a second laser source.

18. The system as claimed in claim 13, wherein the diameter (D_L1) of the first laser source (1) is greater than the particle diameter (D_pmax) of the powdered alloy (2) on the work bed (3).

19. The system as claimed in claim 13, wherein the diameter (D_L2) of the second laser source (17) is smaller than the diameter (D_L1) of the first laser source (1).

20. An additive manufacturing system manufacturing a metallic component by the method as claimed in claim 1.