LA-ICP-MS studies of cross section of NiCrAlY-based coatings on high-temperature alloys

Abstract

A microlocal analytical technique using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was developed to investigate elemental diffusion at the interface of NiCrAlY-based coatings on high-temperature alloys. The surface of the cross section of alloyed sample was scanned with a focused laser beam (diameter of laser crater, 25 μm; wavelength, 213 nm; laser power density, 10¹¹ W cm⁻²), and the laser ablation system was coupled to a double-focusing sector field ICP-MS. The capabilities of LA-ICP-MS using “line scan” and “single point” mode at laser energies of 2 and 4 mJ were compared. Alloy certified reference material (CRM) BAM-328-1 (BAM—Bundesanstalt für Materialprüfung, Berlin, Germany) with a similar matrix composition to the samples investigated was employed to determine the relative sensitivity coefficients (RSCs) of chemical elements to quantify the analytical data. The RSCs of analytes measured by LA-ICP-MS in alloy CRM vary between 0.2 and 2. In addition, other calibration procedures involving calibration curves and solution-based calibration were considered. LA-ICP-MS was used to study the lateral element distribution on NiCrAlY-based alloy and coating after oxidation in air (300, 1000, 5000, 15000 hours) at a temperature of 980 °C, whereby an increasing loss of aluminium due to diffusion from coating into the high-temperature base alloy was observed. Furthermore, the diffusion of several substrate alloying elements (e.g., Co, Ta, Mo, W) into the coating after annealing was found, which could be the reason for the alteration of mechanical properties (high-temperature stability) or oxidation performance or both.