C. Bindal

Mechanical properties of boronized AISI W4 steel

Abstract A series of experiments was performed to evaluate some mechanical properties of boronized AISI W4 steel. Boronizing was carried out in a solid medium consisting of EKabor powders at 850, 950 and 1050°C for 2, 4, 6 and 8 h. After boronizing, FeB and Fe 2 B phases were formed on the surface of the steel substrate. A boride layer was revealed by a classical metallographic techniques and X-ray diffraction (XRD) analysis. Depending on the process temperature and boronizing time, the thickness of the coating layers ranged from 8 to 386 μm. Metallographic studies revealed that the boride layer has a lenticular morphology. The hardness of the boride layer was measured using a Vickers indenter with loads of 0.5 and 1 N. It was found that the hardness of the boride layers ranged from 1407 to 2093 HV. The fracture toughness of borided surfaces was measured via a Vickers indenter with a load of 10 N. It was observed that the fracture toughness of the boride layer ranged from 1.39 to 6.40 MPa m 1/2 . A longer boronizing time results in a greater boride layer thickness. Lengthwise cracks were formed on the samples that were borided at 1050°C for 6 and 8 h. The distribution of alloying elements from the surface to the interior was determined using energy-dispersive X-ray spectroscopy (EDS). The main aim of present study was to increase the service life of AISI W4 plain carbon tool steel.

Mechanical behavior of borides formed on borided cold work tool steel

Abstract In this study, some mechanical properties of borided cold work low-alloy tool steels were investigated. Boronizing was performed in a solid medium consisting of Ekabor-I powders at 1000°C for 2, 4 and 6 h. The substrate used in this study was high-carbon, low-alloy tool steel essentially containing 1.18 wt.% C, 0.70 wt.% Cr, 0.30 wt.% Mn, 0.10 wt.% V and 0.25 wt.% Si. The presence of borides (FeB+Fe 2 B) formed on the surface of steel substrate was confirmed by optical microscope and X-ray diffraction (XRD) analysis. The hardness of the boride layer formed on the surface of the steel substrate and unborided steel substrate were 1854 and 290 kg/mm 2 , respectively. Experimental results revealed that longer boronizing time resulted in thicker boride layers. Optical microscope cross-sectional observation of the borided layers revealed denticular morphology. The fracture toughness of the boride layers measured by means of a Vickers indenter with a load of 3 N was in the range of 2.52–3.07 MPa m 1/2 .

Kinetics of boriding of AISI W1 steel

Abstract A technologically interesting characteristic of boriding is the production of a hard, wear-resistant coating layer on the steel substrate. In this study, case properties of borided AISI W1 steel has been investigated by conducting a series of experiments in Ekabor-I powders at the process temperature of 1123–1323 K at 50 K intervals for periods of 1–8 h. The presence of borides FeB and Fe 2 B formed on the surface of steel substrate was confirmed by optical microscopy and X-ray diffraction. Cross-sectional observation in the optical microscope revealed smooth and compact morphology of the borided layer. The distribution of alloy elements from the surface to the interior was confirmed by energy dispersive X-ray spectroscopy. The hardness of the boride layer formed on the surface of the steel substrate was higher than 1500 HV. It was concluded that the optimum temperature for AISI W1 steel borided in Ekabor-I powders was approximately 1223 K for hardness in 10 μm depth, and the hardness change with boriding temperature was related to the grain size of the treated steel. The kinetics of boriding show a parabolic relationship between layer thickness and process time, and the activation energy for the process is 171.2±16.6 kJ mol −1 . Moreover, an attempt was made to investigate the possibility of predicting the iso-thickness of boride layer variation and to establish an empirical relationship between process parameters of boriding and boride layer.

Fracture toughness of boride formed on low-alloy steels

Abstract In this study, we investigated the fracture toughness of boride layers formed on steel surfaces. The samples used for this study were prepared from low-alloy and low-carbon steels essentially containing Cr and/or Mn as the major elements. Boronizing was done in a salt bath consisting of borax, boric acid, and ferro-silicon. The temperature of the bath was 940 °C and the boronizing was conducted at an atmospheric pressure for 5–7 h. The presence of borides, e.g. Fe 2 B, was revealed by X-ray h diffractometry, SEM, and optical microscopy. The fracture toughness of borided surfaces was measured via Vickers indenters with a load of 2 N. It was found that the fracture toughness of the borides ranged from 4 to 6 MPa 1/2. The fracture toughness of the borides depends strongly on chemical composition of substrate and boronizing time. Mn as an alloying element has a beneficial effect on fracture toughness, and the longer boronizing time results in higher fracture toughness.

Boriding response of AISI W1 steel and use of artificial neural network for prediction of borided layer properties

Abstract In the present study, boriding response of AISI W1 steel and prediction of boride layer properties were investigated by using artificial neural network (ANN). Boronizing heat treatment was carried out in a solid medium consisting of Ekabor-I powders at 850–1050 °C at 50 °C intervals for 1–8 h. The substrate used in this study was AISI W1. The presence of borides FeB and Fe 2 B formed on the surface of steel substrate was confirmed by optical microscope and X-ray diffraction analysis. The hardness of the boride layer formed on the surface of the steel substrate was over 1500 VHN. Experimental results indicated that there is a nearly parabolic relationship between boride layer and process time for higher temperatures. Optical microscope cross-sectional observation of the borided layer revealed columnar and compact morphology. Moreover, an attempt was made to investigate possibility of predicting the hardness and depth of boride layer variation and establish some empirical relationship between process parameter of boriding and boride layer, and hardness changes using back-propagation learning algorithm in ANN. Modelling results have shown that hardness and depth of boride layer were predicted with high accuracy by ANN.

The characterization of borided 99.5% purity nickel

Abstract A series of experiments were performed to evaluate some properties of borided 99.5% purity nickel. Boronizing was carried out in a solid media consisting of Ekabor powders at 950°C for 2, 4, and 8 h, respectively. Data on intermetallic silicides and borides (Ni 5 Si 2 , Ni 2 B) that formed on the surface of nickel substrate during boronizing were confirmed by a classical metallographic technique and X-ray diffraction (XRD) analysis. It was observed that the predominant phase in the coating layer was a silicide. It is probable that the formation of the nickel silicide layer was due to silicon in the boronizing powder. The hardness of silicides was measured by using a Vickers indenter with a load of 0.5 N. The microhardness of silicides formed on the surface of the nickel substrate reached up to 805 HV. Metallographic studies revealed that the silicide layer has an equiaxed granular morphology, whereas the boride layer formed had a needle-shaped structure. Depending on process temperature and boronizing time the thickness of coating layers ranged from 123 to 281 μm. The thickness of silicide and boride layers depended strongly on the processing time at 950°C. The longer boronizing time resulted in the thicker surface layer. The distribution of alloying elements from the surface to the interior was determined using energy dispersive X-ray spectroscopy (EDS).

Microwave–assisted biomimetic synthesis of hydroxyapatite using different sources of calcium

In this study, some properties of biomimetic synthesized hydroxyapatite by using different sources of calcium were investigated. Biomimetic synthesis of hydroxyapatite was carried out in microwave oven using 1.5 simulated body fluid (SBF) solution having different calcium sources with 800W power for 15min. As phosphorus source di-ammonium hydrogen phosphate ((NH4)2HPO4) while for each sample as a calcium sources calcium chloride (CaCl2), calcium nitrate tetra hydrate (Ca(NO3)2·4H2O) and calcium hydroxide (Ca(OH)2) were utilized, respectively. For comparison, precipitation process was also performed in only 1.5 SBF solution without calcium and phosphorus sources. The presence of phases in synthesized hydroxyapatite was confirmed by XRD. The crystallinity and crystalline size of the phases in as synthesized powders were also calculated by using XRD data. It was found that the unique phase is hydroxyapatite (HAp, Ca5(PO4)3(OH)) by using the calcium nitrate tetra hydrate and calcium hydroxide sources, while the dominant phases are tri-calcium phosphates (TCP) and HAp for CaCl2 source and 1.5SBF which does not contain any additional Ca source. SEM studies revealed that nano-hexagonal rods and nano-spherical hydroxyapatites could be synthesized by using this process. Energy-dispersive X-ray spectroscopy (EDS) analysis revealed that the Ca/P ratio near to be as 1.5 which is the value for HAp in bone. Raman and Fourier transform-infrared spectroscopy (FT-IR) results combined with the X-ray diffraction (XRD) indicates that dominantly the present of single phase is HAp. The crystal size and fraction crystallinity of as synthesized HAp powders were changed between 29.5 and 45.4nm and 0.53-2.37, respectively. Results showed that microwave assisted biomimetic synthesis is a promising method for obtaining HAp powders in shorter process time.

Characterization of Plasma Nitrided X32CrMoV33 Die Steel

In this study, nitriding behavior of plasma nitrided X32CrMoV33 die steel was investigated. Nitriding process was carried out at temperatures of 450, 500, and 550°C for treatment time in the range of 2–32 h. Depending on nitriding temperature and time, the thickness of compound layer ranged from 2 µm to 15 µm. The presence of γ′-Fe4N, ϵ-Fe2-3N, α-Fe, and Cr2N phases formed in the compound layer was confirmed by XRD analysis. Using cross-sectional samples and a microhardness indenter, hardness depth profiles were also obtained; it was found that the hardness of compound layer was over 1000 HV. Kinetic studies revealed that the effective diffusion coefficients for plasma nitrided X32CrMoV33 are approximately 40.3 × 10−14, 99.2 × 10−14, and 427 × 10−14 m2s−1 for 450, 500, and 550°C process temperatures, respectively. The activation energy for plasma nitrided X32CrMoV33 steel is 118.77 kJ mol−1.

A tribological comparison of pure and boronized chromium

Boronized metals are potential candidate materials for various industrial applications as well as for joint arthroplasty. This is due to their high hardness and corrosion resistance. In the present research, we investigated the tribological performance of boronized chromium when worn against bearing steel E52100. Pure chromium was used as a control material and tested under similar conditions. Three test conditions were used-dry sliding, with water, and with simulated body fluid (SBF). The highest coefficient of friction obtained was for chromium boride under dry sliding conditions. Water and SBF acted as lubricants and lowered the coefficient of friction. The friction coefficient for Cr and chromium boride was lowest under SBF conditions. SEM analysis showed that the wear modes were different under different test conditions. TEM analysis showed a layered-like structure of debris that could have acted as a lubricant and caused a very low friction coeffi.

An evaluation of human articular cartilage on femoral head

In this study, we investigated stress relaxation behavior of the human articular cartilage on femoral head. Articular cartilage is a white dense connective tissue that covers the bone ends within diarthrodial joints and works as a weight-transmitting and energy-absorbing material. Human articular cartilage on femoral head was used as test material. Relaxation tests were carried out by using the indentation technique via Instron Universal Testing Machine. Test materials were investigated in an isotonic salt solution at 37 °C. To keep the temperature constant, two vessels being in each other were utilized. Thus, hot water was circulated in the outer vessel and isotonic salt solution was kept in the inner vessel. Experimental results showed that there is a remarkable difference between normal and degenerated cartilage for the same age and sex. It was observed that the relaxation percent of normal cartilage as a function of relaxation time is much higher than that of degenerated cartilage.