Impact of Leather on the Fire Resistance of Leather-Wood Fibreboard: FT-IR Spectroscopy and Pyrolysis-GC-MS Investigation

Leather-wood fibreboards are innovative composite materials, which combine together the high mechanical properties of wood with the superior fire behaviour properties of leather. This study deals with the understanding of the combustion mechanism of the wet-white leather panel. During burning, an overlay coating-like surface is formed on top of a foamy structure that creates the heat transfer barrier. The FT-IR spectroscopy results of the leather show the rearrangement of the proteins and the formation of an increasing amount of acid groups when the exposure to hot gun at over 530°C was prolonged. These acid moieties can react with amino groups of other peptide chains, building a protective polymer network which hinders the oxygen to reach the core of the panel. Simultaneously, the gases produced during rearrangement cannot easily leave the material, producing a foamy structure which slows down the heat transfer to the core of the material. The Py-GC-MS analysis shows that the gases produced by the wet-white leather-type protein-based boards were amino-aromatic compounds like the diketopiperazine (DKP), which do not burn easily. The combination of the effects of (i) formation of the overlay coating-like surface, (ii) establishment of the foamy structure, and (iii) degassing of DKP explains the outstanding fire properties of leather and wood-leather fibreboards.

TEM Microstructure and Chemical Composition of Transition Zone Between Steel Tube and An Inconel 625 Weld Overlay Coating Produced by CMT Method

The aim of this work was to investigate the microstructure and chemical composition of the transition zone between 16Mo3 steel and Inconel 625 weld overlay coating produced by the Cold Metal Transfer (CMT) method. Investigations were primarily carried out through transmission electron microscopy (TEM) on thin foils prepared by FIB (Focus Ion Beam).The chemical analysis demonstrated that the amount of certain elements (Fe, Ni, Cr, Mo, Nb) in the transition zone between the base material and the weld overlay changes quickly, from the composition of the steel to the composition of the composite zone. STEM and TEM investigations revealed that two areas are clearly visible in the transition zone. In the narrow band close to the fusion boundary where plates are clearly visible and theMstemperature is higher than room temperature, electron diffraction analyses show reflections of martensite and austenite. Moreover, the crystallographic relations between martensite and austenite can be described by the Kurdjumov-Sachs (K-S) relationship$\{ 110\} _{\alpha '} ||\{ 111\} _\gamma < 1\bar 11 > _{\alpha '} || < 1\bar 10 > _\gamma $). The microstructure of the part of the transition zone with anMstemperature lower than room temperature as well as that of the composite zone is austenite. The investigations proved that the width of the martensitic area can be significantly limited by using the CMT technique for weld overlaying.

Characterization of In Situ Synthesized TiC-TiB2 Reinforced Fe Matrix Wear-Resistant Coating by TIG Arc/Cored-Wires Weld Overlaying Technology

TiC-TiB2/ Fe matrix composite coatings were in-situ synthesized in the surface of Q235 steel substrate by TIG/cored-wire weld overlaying. The microstructure, micro-hardness and wear resistance of the weld overlay coating were investigated using SEM, XRD, Micro-hardness Tester and Pin-disc Wear Tester respectively. The results showed that the weld overlay coating presented a dense microstructure with defect-free of pore and crack, and better metallurgical bond with the substrate; TiC and TiB2 particulate distributed dispersively in Fe matrix of the weld overlay coatings. The highest Micro-hardness of the weld overlaying was 1657.58HV, which is 6 times higher than the substrate, and wear resistance are also improved at the room temperature under normal atmosphere conditions.

Influence of Boiler Pipe Cladding Techniques on their Microstructure and Properties

The aim of this work was to investigate different weld overlay coating technologies applied to steel boiler pipes and their influence on microstructure and properties of the produced overlays. The investigations were carried out on the boiler pipes weld overlaid by an Inconel 625 and cladded at various conditions (CMT, GMAW and GTAW). The investigations showed that microstructure and mechanical properties of overlaid pipes depend on cladding technology and the chemical composition of the base material.