Methods for reducing nonmetallic inclusions in coatings applied by laser surfacing

Abstract

The results of experimental studies based on the analysis of deposited coatings and processing methods aimed at reducing the number of non-metallic inclusions in the process of laser powder cladding are presented. The main purpose of the experiments was to determine the effectiveness of various methods for reducing non-metallic inclusions in deposited coatings. The source of such defects are often oxides and slag on the treated surface, as well as granules of powder material used for applying wear-resistant coatings. Corrosion-resistant heat-resistant steel of the 08X18N10T grade (analog AISI 321) was used as the substrate material, from which samples with dimensions of 100x100x8 mm were made. Cladding was performed using a metallic powder 08Kh17N8S6G (analog of the TSN-6L electrode) with a fractional composition of 63-125 microns, having a spherical particle shape and having good fluidity. Experimental laser cladding was carried out on a laser robotic complex based on an ytterbium fiber laser. Evaluation of nonmetallic inclusions was carried out by metallographic analysis on etched cross-sections of the resulting deposited coatings, as well as by RAMAN spectroscopy. The qualitative dependence of the content of defects, such as gas pores, in the layer of the deposited coating on the crystallization of the melt bath formed during laser powder cladding has been established.

Keywords

• laser cladding
• non-metallic inclusion
• raman spectroscopy
• gas protection
• laser power