Laser metal deposition (LMD) is an additive manufacturing process in which a metal powder or wire is added to a laser-induced molten pool. This localized deposition of material is used for the manufacturing, modification, and repair of a wide range of metal components. The use of wire as feedstock offers various advantages over the use of powder in terms of the contamination of the process environment, the material utilization rate, the ease of handling, and the material price. However, to achieve a stable process as well as defined geometrical and microstructural properties over many layers, precise knowledge on the effects of the input variables of the process on the resulting deposition characteristics is required. In this work, the melt pool temperature was used as an input parameter in LMD with coaxial wire feeding of stainless steel, which was made possible through the use of a dedicated closed-loop control system based on pyrometry. Initially, a temperature range was determined for different process conditions in which a stable deposition was obtained. Within this range, the cause-effect relationships between the melt pool temperature and the resulting geometry as well as the material properties were investigated for individual weld beads. It was found that the melt pool temperature is positively correlated with the width of the weld bead as well as the dilution. In addition, a dependence of the microhardness distribution over the cross section of a weld bead on the melt pool temperature was demonstrated, with an increased temperature negatively affecting the hardness.

https://lia.scitation.org/doi/pdf/10.2351/7.0000773

Metallurgy and Mechanics of Welding

Toward defect-free components in laser metal deposition with coaxial wire feeding through closed-loop control of the melt pool temperature

This thesis is a part of a larger project involving the Faste Laboratory at Lulea University of Technology and the Wingquist Laboratory at Chalmers University of Technology. The interaction betwe ...

background or methods

A new welding modeling approach in simulation driven design

Study and research on arc welding have provided identification of errors in formulas for calculating the cooling time t8/5 and other dependent parameters. It is concluded that large errors are present in certain intervals which had caused fail?ures in welding technologies. Incorrect approximation of cooling temperature is replaced by a more accurate approximation used for defining of the new precise algorithm for determining relevant welding parameters.

/pdf/new-method-for-determining-cooling-time-and-preheating-dxeojepils.pdf

New method for determining cooling time and preheating temperature in arc welding

Welding defects can adversely affect the mechanical properties and performance of products in service. Therefore, a thorough understanding of these defects, how they occur, their severity, and remedies can guarantee high quality products and enhanced performance. The purpose of this review report is to investigate the root causes of welding porosity defect, and suggest measures to minimise or eliminate the defects. To determine the root cause of porosity in a welding process without a grasp of the fundamental principles of the problem can be time consuming, and even a frustrating task. It is therefore necessary to deal with porosity problems through organized problem-solving approach, by identifying the different causes, before we find and eliminate the root cause. The literature survey is concerned with published data and general comments are made on the cause of porosity, mechanisms of porosity formation, and porosity in TIG welding, surface cleaning methods, welding parameter effects on porosity, and issues relating to the welding of ferritic stainless steels and austenitic stainless steels. In discussing the causes of porosity, recommendations have been made on the avoidance of porosity.

background

/pdf/a-review-of-porosity-formation-and-recommendations-on-the-4qblriafcr.pdf

A Review of Porosity Formation and Recommendations on the Avoidance of Porosity in TIG Welding of Steels

Die zum Schweisen verwendeten nahezu punktformigen, konzentrierten Warmequellen beeinflussen und verandern in charakteristischer Weise das Schweisgut und einen gewohnlich nur hochstens einige Millimeter breiten Bereich des Grundwerkstoffes unmittelbar neben der Schmelzgrenze, der als Warmeeinflusszone (WEZ) bezeichnet wird. Das Aus mas der entstandenen Gefugeanderungen und damit der Eigenschaftsanderungen in den schmelzgren zennahen Bereichen ist im Wesentlichen abhangig von:


dem Temperatur-Zeit-Verlauf in diesen Bereichen, d. h. von der Werkstuckdicke, dem gewahlten Schweisverfahren, den Einstellwerten (Schweisstrom, Schweisspannung und Vorschubgeschwindigkeit der Warmequelle) und der Hohe der Vorwarmtemperatur und


der Art des Nahtaufbaus (Ein-, Mehrlagentechnik, Pendellagen, Zugraupen).

Metallurgy and Mechanics of Welding

Citations

Toward defect-free components in laser metal deposition with coaxial wire feeding through closed-loop control of the melt pool temperature

A new welding modeling approach in simulation driven design

New method for determining cooling time and preheating temperature in arc welding

A Review of Porosity Formation and Recommendations on the Avoidance of Porosity in TIG Welding of Steels

Schweißmetallurgie der Eisenwerkstoffe

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