Microstructural evaluation of 316 L composite coatings reinforced with niobium carbide particle produced by laser cladding Gefüge von laserauftraggeschweißten, mit Niobkarbidpartikeln verstärkten 316 L-Verbundwerkstoffbeschichtungen

Abstract

The cladding process offers advantages such as low porosity, minimal dilution, low distortion of substrate, small heat-affected zone, contributing to improving the chemical, physical, and mechanical characteristics of the coatings. Carbides, as a reinforcing element, are frequent in applications prone to wear. In this contribution, an ASTM A36 mild steel was coated with a niobium carbide reinforced AISI 316 L powder filler material under multiple laser deposition parameters. The effect of the studied parameters on the produced samples’ microstructure and the evolution of such microstructure were evaluated. The formation of a dendritic solidification substructure, unusual in laser-processed austenitic stainless steel, was observed, which is attributed to the rise in constitutional supercooling due to the increase in the solute concentration because of the niobium carbide dissolution. Deposits with 10 % niobium carbide exhibited an austenite primary and ferrite secondary type solidification, where the δ-ferrite and the eutectic γ-niobium carbide are simultaneously formed, without the precipitation of M₂₃C₆ carbides. In deposits with 30 % niobium carbide, the microstructure observed is like that of 10 % niobium carbide deposits, with the appearance of equiaxial particles of niobium carbide, which grow competitively with the eutectic γ-niobium carbide, without relation to the constitutional supercooling (G/R) but governed by the cooling rate (G.R).