Papers by Keyword: TRD

Abstract: The thermo-reactive diffusion (TRD) process is used for diffusing an element to the metallic steel substrate. TRD is carried out by using either salt bath or fluidized bed methods. In this research, the molten salt bath method is used. Ferro chromium was dissolved in the molten borax as the source of chromium in the salt. Samples of cylindrical shape of plain carbon steel with 10 mm diameter and 20 mm height were treated at 1000°C for 14 hours in different baths including either low carbon ferro chromium (LCFC) or high carbon ferro chromium (HCFC) powder. The purpose of this research is to investigate the effect of the salt bath composition on the diffusion of chromium and formation of chromium compound layer on plain carbon steel by using the salt bath method. The coating thickness layers were measured by SEM. The different phases formed on the samples, due to different amounts of carbon in treating salt bath, were determined by X-ray diffraction. It was found that in molten borax salt with high carbon content (high carbon ferro chromium) very few amount of chromium diffused into the plain carbon steel. The thickness of the diffused chromium layer in low and high carbon content ferro chromium in molten borax, is around 32±8 µm and 6.8±1.2 µm, respectively. A number of tests were conducted to address this effect.

Abstract: Thermo-diffusion coatings containing Nitrogen, Carbon and Niobium (N+C+Nb) on AISI D2 steel have been carried out by an initial tufftriding process followed by saturation with Niobium. The properties of the diffusion layer, namely microstructure, phase composition and micro-hardness of the Niobium carbonitride layer, have been studied. The influence of treatment time of Niobizing on the thickness of the metallized layer and its phase composition has been studied. Nitriding treatment was performed at 575°C for 2 h. Then, the Niobizing treatment was performed by pack method in the powder mixture consisting of ferro-Niobium, ammonium chloride and alumina at 1000°C for 1–4 h. The phases formed on the Niobium carbonitride coated steel were NbN and NbC, confirmed by X-ray diffraction (XRD) analysis. The longer the treatment times, the thicker the Niobium carbonitride layer became. The thickness of Niobium carbonitride layer was changing between 6.53 3m and 17.45 3m, depending on treatment time and temperature. The microhardness of Niobium carbonitride layer formed on the AISI D2 steel was changing between 2132±203 and 2814±245 HV0.01 from surface to interior.