Microstructural characterisation of laser surface treated AISI 1040 steel with portable X-ray stress analyzer

Abstract

An experimental study was performed for non-destructive microstructural characterisation of laser surface treated AISI 1040 steel specimens with a portable X-ray diffraction based residual stress analysis system. Laser treated specimens were characterised by residual stress and (211) ferrite peak width measurements, and results were compared with those obtained by optical microscopy. The techniques were sensitive enough to distinguish four different cases arising during laser surface treatment, namely, no transformation hardening, insufficient hardening, adequate transformation hardening and surface melting. On the laser treated surface, the extents of laser melted zone and various microstructural zones of solid state transformation hardened region could be clearly identified. Although both the techniques provided fair estimate of total width of laser treated region, ferrite peak width is a more sensitive parameter to record microstructural transitions involving change in tetragonality of martensite. The technique has a potential for in situ microstructural analysis of ferritic steel weldments.

Precision and accuracy of stress measurement with a portable X-ray machine using an area detector

“…Currently, there are many competing efforts developing high-resolution portable X-ray devices 2 for industrial applications. Initially these were targeted for the steel industry (Ganesh et al, 2013;Farrell, 2010), but applications are expanding alongside the shrinking scale of functional materials. Despite the obvious benefits of a portable device, there have been no objective evaluations of the uncertainty budget of advanced, commercial, portable X-ray units from third parties without conflict of interest.…”

Non-destructive Micro-structural Characterization of Metallic Specimens with a Portable X-ray Diffraction based Residual Stress Analyzer

“…The micro-structure of laser hardened zone displayed steep micro-structural gradient ranging from homogenous lath martensite near the surface and in-homogenous martensite (in terms of its morphology) to dual phase martensite + pro-eutectoid ferrite microstructure at the bottom of laser hardened track. Similar micro-structural transitions were also recorded across the width of LHZ (Ganesh et al 2013a). Table 1 summarizes dimensions of laser hardened zone (scanned with 8 mm/s), estimated based on results of residual stress and peak width profiles, along with actual measurements determined by metallographic examination.…”

“…In the present case study, laser transformation hardening of AISI 1040 steel specimens (30 x 30 x 5 mm) was achieved by scanning surface of the steel specimens with an elliptical shaped (major axis: 11 mm; minor axis: 1 mm) CW CO 2 laser beam of 2.5 kW power at different speeds (5 -13 mm/s) (Ganesh et al, 2013a). In this study, residual stress analysis system was used to determine micro-structural state of laser treated surface and also (ii) determine total width of laser hardened zone and compare them with the corresponding information obtained by metallographic examination.…”