Characterization and Fracture Toughness on AISI 8620 with Hard Coatings

Abstract

The present studies characterize and evaluate the fracture toughness at the surface AISI 8620 with hard coating. The hard coatings FeB and Fe2B were formed using the boriding dehydrated paste at temperatures 1223 and 1273 K with 6 and 8 h exposure time, respectively. The presence of hard coatings formed on the surface AISI 8620 were confirmed by the classical metallographic technique combined with X-ray diffraction analysis. The distribution of alloying elements was determined by Energy Dispersive Spectroscopy (EDS). The fracture toughness of the hard coatings on AISI 8620 was estimated using a Vicker microindentation induced fracture testing of 15 and 35 μm from the surface, applying four load (0.49, 0.98,1.96 and N). The microcrack generated at the corner of the microindentation was considered as an experimental parameter and the tree model Palmqvist crack model was employed to determine the fracture toughness. The adherence of the hard coatings/substrate was evaluate in qualitative form though the VDI 3198 by testing Rockwell C and observed by Scanning Electron Microscopy (SEM). The formation of hard layers was obtained in the range of 100-130 μm, results of XRD present phases FeB, Fe2B, CrB and MnB, the values obtained of Kc are in the range of 2.3 to 4.1 MPam1⁄2 and results of acceptable adhesion HF4 patterns for conditions 6 h of treatment

Characterization and Study Hard Layer on Steels Grade Machinery

“…During the last decade, research has defined that the atoms are deposited on the surface of substrates and their small size and high mobility, these boron atoms diffuse into substrates, and some of them react with atoms of the substrate to form different morphology iron borides (jagged acicular shape and flat); we it can be formed, a single layer or duplex layer depending the chemical composition and the methodology of boriding [4][5][6]. The boriding is a thermochemical surface treatment to improve the mechanical properties surface (hardness, resistance to mechanical and corrosive wear, etc) of metals, alloys and steels [7][8][9]. The mechanical properties of the boride layers are important for industry, as materials nowdays that increase productive manufacturing are required, as their life is lengthened in industrial use, so the evaluation of the properties of the phases present in the material will emphasize boriding to have a range of resistant materials for the manufacturing industry [10][11][12].…”