Evaluation of the diffuse reflectivity behaviour of the melt pool during the laser metal deposition process

2016 ◽  
Author(s):  
Dieter De Baere ◽  
Wim Devesse ◽  
Ben De Pauw ◽  
Michaël Hinderdael ◽  
Patrick Guillaume
Keyword(s):  
Deposition Process ◽  
Metal Deposition ◽  
Laser Metal Deposition ◽  
Melt Pool ◽  
Diffuse Reflectivity

Vision-based defect detection in laser metal deposition process

2014 ◽  
Vol 20 (1) ◽  
pp. 77-85 ◽  
Author(s):  
Shyam Barua ◽  
Frank Liou ◽  
Joseph Newkirk ◽  
Todd Sparks
Keyword(s):  
Defect Detection ◽  
Detection System ◽  
Vision System ◽  
Low Cost ◽  
Deposition Process ◽  
Metal Deposition ◽  
Cooling Curve ◽  
Laser Metal Deposition ◽  
Content Type ◽  
Melt Pool

Purpose – Laser metal deposition (LMD) is a type of additive manufacturing process in which the laser is used to create a melt pool on a substrate to which metal powder is added. The powder is melted within the melt pool and solidified to form a deposited track. These deposited tracks may contain porosities or cracks which affect the functionality of the part. When these defects go undetected, they may cause failure of the part or below par performance in their applications. An on demand vision system is required to detect defects in the track as and when they are formed. This is especially crucial in LMD applications as the part being repaired is typically expensive. Using a defect detection system, it is possible to complete the LMD process in one run, thus minimizing cost. The purpose of this paper is to summarize the research on a low-cost vision system to study the deposition process and detect any thermal abnormalities which might signify the presence of a defect. Design/methodology/approach – During the LMD process, the track of deposited material behind the laser is incandescent due to heating by the laser; also, there is radiant heat distribution and flow on the surfaces of the track. An SLR camera is used to obtain images of the deposited track behind the melt pool. Using calibrated RGB values and radiant surface temperature, it is possible to approximate the temperature of each pixel in the image. The deposited track loses heat gradually through conduction, convection and radiation. A defect-free deposit should show a gradual decrease in temperature which enables the authors to obtain a reference cooling curve using standard deposition parameters. A defect, such as a crack or porosity, leads to an increase in temperature around the defective region due to interruption of heat flow. This leads to deviation from the reference cooling curve which alerts the authors to the presence of a defect. Findings – The temperature gradient was obtained across the deposited track during LMD. Linear least squares curve fitting was performed and residual values were calculated between experimental temperature values and line of best fit. Porosity defects and cracks were simulated on the substrate during LMD and irregularities in the temperature gradients were used to develop a defect detection model. Originality/value – Previous approaches to defect detection in LMD typically concentrate on the melt pool temperature and dimensions. Due to the dynamic and violent nature of the melt pool, consistent and reliable defect detection is difficult. An alternative method of defect detection is discussed which does not involve the melt pool and therefore presents a novel method of detecting a defect in LMD.

scholarly journals Influence of Process Parameters and Deposition Strategy on Laser Metal Deposition of 316L Powder

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1160 ◽  
Author(s):  
Federico Mazzucato ◽  
Alberta Aversa ◽  
Roberto Doglione ◽  
Sara Biamino ◽  
Anna Valente ◽  
...  
Keyword(s):  
Deposition Process ◽  
Metal Deposition ◽  
Process Window ◽  
Laser Metal Deposition ◽  
Scanning Strategy ◽  
Influence Of Process Parameters ◽  
Melt Pool ◽  
Manufacturing Technologies ◽  
Blown Powder ◽  
Building Parameters

In blown powder additive manufacturing technologies the geometrical stability of the built parts is more complex with respect to more conventional powder bed processes. Because of this reason, in order to select the most suitable building parameters, it is important to investigate the shape and the properties of the single metal bead formation and the effect that a scan track has on the nearby ones. In the present study, a methodology to identify an appropriate laser metal deposition process window was introduced, and the effect of the building parameters on the geometry of circular steel samples was investigated. The effect of the scanning strategy on the deposited part was also investigated. This work draws the attention to the importance of the obtainment of the most suitable melt pool shape, demonstrating that the laser power and the scanning strategy have a strong influence not only on the shape but also on the mechanical properties of the final component.

Spectroscopic monitoring and melt pool temperature estimation during the laser metal deposition process

2016 ◽  
Vol 28 (2) ◽  
pp. 022303 ◽  
Author(s):  
Dieter De Baere ◽  
Wim Devesse ◽  
Ben De Pauw ◽  
Lien Smeesters ◽  
Hugo Thienpont ◽  
...  
Keyword(s):  
Deposition Process ◽  
Metal Deposition ◽  
Laser Metal Deposition ◽  
Temperature Estimation ◽  
Spectroscopic Monitoring ◽  
Melt Pool ◽  
Melt Pool Temperature

scholarly journals Simulation of thermal behaviours and powder flow for direct laser metal deposition process

2018 ◽  
Vol 190 ◽  
pp. 02001
Author(s):  
Quanren Zeng ◽  
Yankang Tian ◽  
Zhenhai Xu ◽  
Yi Qin
Keyword(s):  
Cfd Simulation ◽  
Effective Means ◽  
Flow Distribution ◽  
Fem Analysis ◽  
Deposition Process ◽  
Metal Deposition ◽  
Powder Flow ◽  
Laser Metal Deposition ◽  
Melt Pool ◽  
Direct Laser

Laser engineering net-shaping (LENS), based on directed energy deposition (DED), is one of the popular AM technologies for producing fully dense complex metal structural components directly from laser metal deposition without using dies or tooling and hence greatly reduces the lead-time and production cost. However, many factors, such as powder-related and laser-related manufacturing parameters, will affect the final quality of components produced by LENS process, especially the powder flow distribution and thermal history at the substrate. The powder concentration normally determines the density and strength of deposited components; while the thermal behaviours of melt pool mainly determines the cooling rate, residual stress and consequent cracks in deposited components. Trial and errors method is obviously too expensive to afford for diverse applications of different metal materials and various manufacturing input parameters. Numerical simulation of the LENS process will be an effective means to identify reasonable manufacturing parameter sets for producing high quality crack-free components. In this paper, the laser metal powder deposition process of LENS is reported. The gas-powder flow distribution below the deposition nozzle is obtained via CFD simulation. The thermal behaviours of substrate and as-deposited layer/track during the LENS process are investigated by using FEM analysis. Temperature field distributions caused by the moving laser beam and the resultant melt pool on the substrate, are simulated and compared. The research offers a more accurate and practical thermal behaviour model for LENS process, which could be applied to further investigation of the interactions between laser, melt pool and powder particles; it will be particularly useful for manufacturing key components which has more demanding requirement on the components’ functional performance.

scholarly journals Study of the Influence of Shielding Gases on Laser Metal Deposition of Inconel 718 Superalloy

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1388 ◽  
Author(s):  
Jose Ruiz ◽  
Magdalena Cortina ◽  
Jon Arrizubieta ◽  
Aitzol Lamikiz
Keyword(s):  
Metal Deposition ◽  
Slight Reduction ◽  
Laser Metal Deposition ◽  
Melt Pool ◽  
Industrial Sectors ◽  
Inconel 718 Superalloy ◽  
Melt Pool Temperature ◽  
Different Gases ◽  
Die And Mold

The use of the Laser Metal Deposition (LMD) technology as a manufacturing and repairing technique in industrial sectors like the die and mold and aerospace is increasing within the last decades. Research carried out in the field of LMD process situates argon as the most usual inert gas, followed by nitrogen. Some leading companies have started to use helium and argon as carrier and shielding gas, respectively. There is therefore a pressing need to know how the use of different gases may affect the LMD process due there being a lack of knowledge with regard to gas mixtures. The aim of the present work is to evaluate the influence of a mixture of argon and helium on the LMD process by analyzing single tracks of deposited material. For this purpose, special attention is paid to the melt pool temperature, as well as to the characterization of the deposited clads. The increment of helium concentration in the gases of the LMD processes based on argon will have three effects. The first one is a slight reduction of the height of the clads. Second, an increase of the temperature of the melt pool. Last, smaller wet angles are obtained for higher helium concentrations.

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