Core-shell morphology of welding fume micro- and nanoparticles

Welding fume particles were analyzed using low energy ion erosion in secondary ion mass spectrometry. The particles were collected during the welding process of steel performed with three different techniques: electron beam welding (EBW), gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW). The first process was performed in vacuum while the two others in atmosphere. A 300-400 nm diameter fraction of particles emitted in atmosphere was separated using a nine-stage impactor. Ion erosion of particles embedded in indium substrates was performed with 2 keV, 100 mum diameter, Ar+ ion beam at 45degrees ion incidence angle with respect to the substrate surface. The results show that all three types of particles have core-shell morphology. Particles formed in vacuum (EBW) have a shell enriched in oxygen, fluorine, chlorine, and potassium, with respect to the core composed mainly of iron, chromium and manganese. The GTAW particles are more oxidized than the EBW particles. Chlorine and fluorine dominate in the shell, however, their concentration in the core is higher than in the EBW particles. The SMAW particles are oxidized much more than two other types of particles. The shell is rich in chlorides, fluorides and potassium while the core is composed mainly of iron, chromium and manganese oxides. (C) 2003 Elsevier Science Ltd. All rights reserved.