Defect detection in laser powder deposition components by laser thermography and laser ultrasonic inspections

Abstract

Laser Powder Deposition (LDP) techniques are being adopted within aerospace and automotive manufacturing to produce innovative precision components. Non-destructive techniques (NDT) for detecting and quantifying flaws within these components enables performance and acceptance criteria to be verified, improving product safety and reducing ongoing maintenance and product repair costs.In this work, software enabled techniques are presented for in-process analysis of NDT laser ultrasonic signals and pulsed laser thermography images of sequential metallic LPD layers. LPD tracks can be as thin as 200µm while deposited at a rate of 500 mm/min, requiring ultrafast inspection and processing times. The research developed analysis algorithms that allow senior engineers to develop inspection templates and profiles for in-process inspection, as well as an end-to-end, user friendly interface for engineers to perform complete manual Laser Ultrasonic or Laser Thermographic inspections.Several algorithms are offered to quantify the flaw size. location and severity. The identified defects can be imported into a sentencing engine which then automatically compares analysis results against the user defined acceptance criteria so that the manufacturing products can be verified. Where both laser ultrasonic and laser thermographic NDT data is available further statistical tools could increase the confidence level of the inspection decision.

Non-Destructive Testing Inspection for Metal Components Produced Using Wire and Arc Additive Manufacturing

“…In-line laser thermography testing involves shining a laser onto the surface of the WAAM part while it is being built. The laser heats the surface, causing it to emit infrared radiation [57]. A thermal imaging camera is then used to capture the emitted radiation and create a thermal image of the object.…”

“…A thermal imaging camera is then used to capture the emitted radiation and create a thermal image of the object. By analyzing the thermal image, it is possible to detect areas of the object that are hotter or cooler than others, which can indicate the presence of defects or inconsistencies in the WAAM part [31,57].…”

A Review of Diagnostics Methodologies for Metal Additive Manufacturing Processes and Products

“…Defect information is produced to identify processing errors and modify processing parameters in real time [ 77 ]. The use of LUT generating a Rayleigh wave in power direct energy (PDE) deposition metallic samples has been done for a small number of studies in which discontinuities between 150 and 500 were observed at a depth of up to 700 , which were considered surface or close to surface defects [ 78 ]. Another work reported and proved the possibility of using LUT generating a Lamb wave to detect the natural formatted [ 79 ] and artificial [ 80 ] defects inside a printed Ti6Al4V block.…”

An investigation on the suitability of modern nondestructive testing methods for the inspection of specimens manufactured by laser powder bed fusion

“…With the profile images (B-scans), the minimum detectable diameter was 0.725 mm for defects at a depth up to 0.7 mm . Further studies have been conducted applying ultrasonic testing (UT) for in situ monitoring [28][29][30][31][32][33].…”