Product Code: ICAL07_P505

Quantitative Analysis of Retained Austenite in Laser Melted Martensitic Stainless Steel
Authors:
Tshidiso Seleka, CSIR National Laser Centre; Pretoria Southwest Africa
Marie Ulbrich, Vaal University of Technology; Pretoria Southwest Africa
Sisa Pityana, CSIR National Laser Centre; Pretoria Southwest Africa
Lipson Rampedi, CSIR National Laser Centre; Pretoria Republic of South Africa
Presented at ICALEO 2007

An AISI 420 martensitic stainless steel, 0.6 mm thick was melted with a 4.4 Kw continuous wave Nd: Yag laser in order to induce a certain proportion of retained austenite in a matrix. The volume percentage of the retained austenite in the melted-surface layer was investigated by irradiating the surface at different processing conditions. Typically, the sample was melted at different nominal laser beam powers (P), beam scanning speeds (v), and shielding gases, at constant beam diameter (d). The objective of this study was to determine if X-ray diffraction (XRD) was sufficient for quantifying the volume percentage of retained austenite. After a preliminary qualitative analysis, a Rietveld full pattern refinement program was used to quantify the volume percentage of the retained austenite in the melted-surface layer. The results show that the volume fraction of retained austenite in laser melted layer increased with decreasing energy density, when laser melting was carried out in an inert atmosphere.