Real time monitoring of laser beam welding keyhole depth by laser interferometry

Abstract

The utility of a new laser interferometric technique, inline coherent imaging, for real time keyhole depth measurement during laser welding is demonstrated on five important engineering alloys. The keyhole depth was measured at 200 kHz with a spatial resolution of 22 mm using a probe beam, which enters the keyhole coaxially with the process beam. Keyhole fluctuations limited average weld depth determination to a resolution on the order of 100 mm. Real time keyhole depth data are compared with the weld depths measured from the corresponding metallographic crosssections. With the exception of an aluminium alloy, the technique accurately measured the average weld depth with differences of less than 5%. The keyhole depth growth rates at the start of welding are measured and compare well with order of magnitude calculations. The method described here is recommended for the real time measurement and control of keyhole depth in at least five different alloys.

In situ morphology-based defect detection of selective laser melting through inline coherent imaging

“…The ICI signature observed in this processing regime is consistent with ICI measurements taken of bead-on-plate laser keyhole welding processes (Blecher et al, 2014). The existence of a vapor channel during processing allows imaging beam penetration below the substrate level and subsequent measurement of keyhole depth.…”

“…Work by Blecher et al (2014) demonstrated the ability of ICI to measure laser keyhole depths in a range of metals, including DH36 steel, 304 stainless steel, Inconel 690, Ti-6Al-4V, and 2219 aluminum alloy. Webster et al (2014) exploited the utility of ICI for feedback control in high-power laser welding applications.…”

Keyhole formation and thermal fluid flow-induced porosity during laser fusion welding in titanium alloys: Experimental and modelling

“…Thus, for the joining of complex components, traditional fusion welding techniques still hold considerable importance [1,2], as these processing routes allow for reasonable joint integrity. Fusion welding processes include the older-type arc-welding methods such as TIG, MIG and laser-arc hybrid welding [3][4][5], and newer beam-welding methods such as laser and electron-beam [6]. The beam processes enable the heat source to become more focused, allowing the molten pool region to form a narrower, deeper weld.…”

OCT for Efficient High Quality Laser Welding

“…Up to now, OCT was successfully used for welding quality control particularly for online high speed profiling of keyhole depth [4]. By implementing the principles and algorithms of the WELDEYE software platform, optimally adapted to the OCT system, fast and exact estimation of the welding location, the maximum keyhole depth which gives an evidence about the power of the processing laser, and the detection of the quality of the resulted weld are possible.…”