Thermo-reactive Deposition Process Research Articles

Wear Resistance of Niobium Carbide Layers Produced on Gray Cast Iron by Thermoreactive Treatments

Gray cast iron is commonly used due to its high damping capacity, machinability and low cost, due to the presence of free graphite and the high fluidity of the molten metal which facilitates the casting of complex parts with thin walls. Suitable coatings can increase gray cast iron wear resistance and expand its usage range. The high hardness of niobium carbide indicates that it may be a good candidate for this purpose. In this work, samples of gray cast iron with composition 3.47% C-2.39% Si-0.55% Mn-0.15% Ni-0.65% Cu-balance Fe were subjected to two thermoreactive niobizing treatments. The first process (a pack treatment) utilized a powder mixture composed of iron niobium, NH4Cl, Al2O3 at 900 °C during 2 h. The second treatment, a thermoreactive deposition process (TRD), utilized a liquid molten bath of sodium borate and iron niobium performed at 900 °C for 2 h. X-ray diffraction (XRD), Vickers hardness, micro-adhesive (fixed-ball) and micro-abrasive (free-ball) wear tests were used to characterize the treated samples. Hardness layers of 2000 HV, typical for niobium carbides, were obtained. Wear tests demonstrated a substantial increase (2 to 12 times higher than that the substrate) in wear resistance obtained with niobizing treatments.

Effect of FeCr/FeV Ratio During Thermo-Reactive Deposition(TRD) Process on Mechanical Properties and Characteristics of Carbide Layer of SUJ2 Steel

Abstract Pack thermo-reactive deposition (TRD) process has been carried out on SUJ2 (AISI 52100) steel substrate, with different wt.% ratio of FeCr/FeV coating powder. In general, TRD process is able to produce several types of hard layer, e.g. carbide, nitride, or carbonitride layer to improve steel surface hardness and wear resistance. In this work, the FeCr/FeV coating powder ratio used were 15/85, 36/65, and 50/50 wt.%. The TRD process temperature was set at 980°C and held for 6 hours. Characterization was performed using microhardness tester, optical microscope and X-ray diffraction (XRD). The characterization results showed that the higher FeV ratio, the higher the hardness and the thicker the layer. The layer thicknesses of 17, 24.1, and 24.6 μm with the average microhardness value was 1989, 2148, and 2296 HV, for 50%, 65% and 85% FeV ratio, respectively. Similar with the hardness result, the lowest wear rate at 3.4x10-4 mm3/m was obtained at 15FeCr/85FeV wt.% ratio. XRD identification showed that mixing the FeCr and FeV powder was successfully producing vanadium. chromium, and complex carbide layer on the surface of steel substrate. Several possible phases that formed in the layer were. V6C5, V8C7, Cr7C3, Cr3C6, VCr2C2, and Cr2Fe14C.

Multilayer-Forming Behavior of Cr Nitrides and Carbides for Thermoreactive Deposition

The effect of a nitride layer on the forming behavior of CrN and (Cr, Fe)7C3 multilayers for thermoreactive deposition (TRD) was investigated. Plasma nitriding followed by TRD (PN-TRD) produced a larger coating thickness than the case of direct TRD with no plasma nitriding. For PN-TRD, an Fe2-3N layer of 10 μm in thickness was produced on AISI 52100 steels using plasma nitriding, followed by TRD using a mixed powder composed of 30 wt % Cr, 2 wt % NH4Cl, and 68 wt % Al2O3. During TRD at 800 °C, a CrN layer of 2 μm in thickness was formed along with a thin layer of mixed carbide (Cr7C3) and nitride (CrN) on top. As the deposition temperature was increased to 950 °C, a new layer of Cr7C3 was formed underneath the outermost layer composed of mixed Cr7C3 and CrN. At 950 °C, a Cr-rich zone indicated a thickness of ~7 μm. As the deposition time increased to 3 h at 950 °C, a new layer of (Cr, Fe)7C3 was produced at the interface between the CrN formed at 800 °C and the base metal. This layer formed because of the abundant resources of Cr and C provided from the TRD powder and base metal, respectively. The multilayer and interface were concretely filled without the formation of voids as the TRD time increased to 6 h at 950 °C. The TRD process on a pre-nitrided layer was successfully applied to produce multilayers of CrN and Cr7C3.

Corrosion Properties of CrAlN and TiAlN Coatings Deposited by Thermoreactive Deposition Process

O. Cegil, B. K l nc, S. Sen and U. Sen Korfez Technical and Industrial Vocational High School, Department of Metal Technology 41780, Korfez/Kocaeli, Turkey Department of Metallurgical and Materials Engineering, Institute of Arts and Sciences, Sakarya University Esentepe Campus, 54187 Sakarya, Turkey Department of Metallurgical and Materials Engineering, Engineering Faculty, Sakarya University Esentepe Campus, 54187 Sakarya, Turkey

Chromium carbonitride coating produced on DIN 1.2210 steel by thermo-reactive deposition technique: Thermodynamics, kinetics and modeling

A duplex surface treatment on DIN 1.2210 steel has been developed involving nitriding and followed by chromium thermo-reactive deposition (TRD) techniques. The TRD process was performed in molten salt bath at 550, 625 and 700°C for 1–14h. The process formed a thickness up to 9.5μm of chromium carbonitride coatings on a hardened diffusion zone. Characterization of the coatings by means of scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) indicates that the compact and dense coatings mainly consist of Cr(C,N) and Cr2(C,N) phase. All the growth processes of the chromium carbonitride obtained by TRD technique followed a parabolic kinetics. Activation energy (Q) for the process was estimated to be 185.6kJ/mol of chromium carbonitride coating. A model based on genetic programming for predicting the layer thickness of duplex coating of the specimens has been presented. To construct the model, training and testing was conducted by using experimental results from 82 specimens. The data used as inputs in genetic programming models were five independent parameters consisting of the pre-nitriding time, ferro-chromium particle size, ferro-chromium weight percent, salt bath temperature and coating time. The training and testing results in genetic programming models illustrated a strong capability for predicting the layer thickness of duplex coating.

Application of ANFIS for modeling of layer thickness of chromium carbonitride coating

In the present work, layer thickness of duplex coating made from thermo-reactive deposition and diffusion has been predicted by Adaptive network-based fuzzy inference systems (ANFIS). A duplex surface treatment on five steels has been developed involving nitrocarburizing and followed by chromium thermo-reactive deposition (TRD) techniques. The TRD process was performed in molten salt bath at 550, 625 and 700 °C for 1–30 h. The process formed a thickness up to 9.5 μm of chromium carbonitride coatings on a hardened diffusion zone. A model based on ANFIS for predicting the layer thickness of duplex coating of the specimens has been presented. To build the model, training and testing using experimental results from 84 specimens were conducted. The data used as inputs in ANFIS models are arranged in a format of twelve parameters that cover the chemical composition (C, Mn, Si, Cr, Mo, V, W), the pre-nitriding time, ferro-chromium particle size, ferro-chromium weight percent, salt bath temperature and coating time. According to these input parameters, in the Adaptive network-based fuzzy inference system models, the layer thickness of duplex coating of each specimen was predicted. The training and testing results in ANFIS models have shown a strong potential for predicting the layer thickness of duplex coating.

Kinetics of V(N,C) and Nb(N,C) coatings produced by V–Nb–RE deposition technique

A duplex surface treatment on AISI H13 steel has been developed involving nitrocarburizing and followed by vanadium niobium and rare earths (V–Nb–RE) thermo-reactive deposition (TRD) techniques. The TRD process was performed in molten borax salt bath at 1223, 1283 and 1343K for 1–4h, respectively. The process formed a thickness of 6 to 35μm of vanadium carbonitride and niobium carbonitride coatings on a hardened diffusion zone. Characterization of the coatings by means of scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) indicates that the compact and dense coatings mainly consist of V8C7, NbC, NbN and VN phases. The value of Vickers hardness of the coatings was up to 1350 HV0.1 after tempering at 848K for 2h. All the growth processes of the vanadium carbonitride and niobium carbonitride coatings obtained by V–Nb–RE deposition technique followed a parabolic kinetics. Activation energy (Q) for the process was estimated to be 215.68kJ/mol of vanadium carbonitride coating, and 134.32kJ/mol of niobium carbonitride coating. Under certain conditions, the values of Q were greater than single vanadizing and deposition niobium. However, growth rate constant (K) was very similar among pairs of them.

Structural Characterization of Titanium Nitride Coatings on AISI M2 Steel

In this work, some surface properties of AISI M2 steel were improved by a thermoreactive deposition process. Gas nitriding was realized on AISI M2 steel at 550°C for 2 h in an ammoniac atmosphere and then, titanizing treatment performed on pre-nitrided steel in the powder mixture consisting of ferro-titanium, ammonium chloride and alumina at 1000°C for 1-4 h. Structural characterization of titanium nitride layer formed on the surface of AISI M2 steel was carried out by using optical microscopy, scanning electron microscopy, electron microprobe and Xray diffraction (XRD) analysis. The hardness measurements of titanium nitride layer were conducted under 10 g loads by using Vickers microhardness indenter. Structural analysis studies showed that titanium nitride layers formed on the AISI M2 steel samples were smooth, compact and homogeneous. XRD analysis show that the coating layer formed on the steel samples includes TiN, Fe6Mo7N2, C0.7N0.3Ti, C0.3N0.7Ti and V2N phases. The hardness of titanium nitride layers formed on the steel samples is between 2040±186 and 2418±291 HV0.01. The thickness of titanium nitride layer formed on the steel samples ranged from 3.86±0.43 9m to 6.13±0.47 9m, depending on treatment time.