Engineering and Technology Journal

High chromium white cast iron (HCWCI) is used in mining, crushing plants, as mill liners, and in the manufacture of grinding balls. The grinding ball is the essential element in fine fragmentation. It must have an excellent life to counter extreme wear and impact conditions that it undergoes. Hence it is important to improve its mechanical properties. This study aims to find the effect of tempering temperature on microstructure, hardness, and abrasive wear of High Chromium White Cast Iron used in the manufacture of grinding balls. In this study, the balls in high chromium white cast iron with 12 to 17% Cr, of 50mm and 70mm in diameter were austenitized at 950°C for 45 min and 55 min for the balls of 50 and 70mm then were quenched in forced air. The balls were tempered at 250°C, 400°C, and 600°C for 120 min and 180 min for both diameters 50 and 70mm respectively, and cooled in the furnace. The results showed that tempering practiced at 250°C and 400°C gives an excellent hardness than balls austenitized at 950°C. It is about 60 HRC and it drops to less than 50 HRC for the tempering at 600°C. This tempering causes a significant mass loss (short life) but tempering at 250°C and 400°C decreases this loss by up to 1.6%. The results of XRD showed the presence of the martensite and carbides type M₇C₃ after tempering at 250°C and a ferritic matrix after tempering at 600°C.

Because of the unique properties, Ni-Ti based shape memory alloys (SMAs) are increasingly attractive for a wide variety of engineering applications such as actuators, biomedical, or robot coupling. In this work, a third alloying element, namely nanoparticles of Ag (which is insoluble in Ni-Ti matrix), is added by powder technology to the Ni-Ti alloy to produce a Ni-Ti-Ag alloy. The Nanoparticles of the Ag element are added at 3, 5, 7, and 10 wt. % to produce four alloy specimens with different mixtures .The mixing process was done by a horizontal mixer for 120 min with a speed of 350 rpm, and then the mixture was compacted by using a compacting pressure of 600 MPa. Afterward, the compacted specimens were sintered at 600 /min for 6 hrs. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to evaluate the microstructure and phases of the products. DSC examination was used to characterize the phase transformation temperatures in heating and cooling. Wear behavior was defined by using the pin-on-disc technique, and the hardness of the samples was calculated using Vickers's hardness apparatus. The results of this work showed that the nano-Ag added at 7 and 10 wt. % were distributed homogeneously in the Ni-Ti matrix, and that Ag slightly decreased hardness and increased the wear rate. The value of shape memory effect (SME) for the produced alloy was about 89.9% and the phase transformation in heating was at a temperature of about 186.48 and in cooling of about 140.3 for the specimen that contains 10 wt.% Ag nanoparticles.

In the present work, the dry sliding wear behavior of Al-12wt%Si matrix nanocomposites reinforced with single addition of 4wt.% Al2O3 or 4wt.%TiO2 nanoparticles, and with hybrid addition of 4wt% (Al2O3 +TiO2) nano particles is investigated. All nanocomposites samples were fabricated by powder technology by mechanical milling of the base alloy (Al-12wt%Si) powder and nanopowders of Al2O3 and TiO2, followed by cold pressing at 100bar and sintering at 520 oC for 90min. Vickers hardness test was done by using Vickers hardness tester. Archimedes technique was used to measure the density of sintered samples and porosity calculated as physical tests of sintered samples. Also AFM, SEM were used to investigate the morphology of mixed powders and nanocomposites samples.
Pin – on Disc wear tests were carried out at room temperature under dry sliding conditions with using different normal loads and sliding times. Worn surface micrographs were investigated based on the optical and scanning electron microscopy observations of wear tracks and wear debris morphology. It has been found that nanocomposite with 4wt% Al2O3 nanoparticles shows the highest hardness than other nanocomposites. It was observed that the wear rate or weight loss of the base alloy and nanocomposite samples increases with the increase in applied load and sliding time. But the nanocomposites samples showed lower wear rate than the base alloy within the same conditions.

This work is concerned with a study of dry sliding wear of Aluminum bace alloy of (Al-4%Cu) reinforcement by silicon carbide particles with different percentage (3, 6,9,12 wt %SiC). Composite materials prepared by stir casting method using vortex technique. The base alloy and composite materials samples were tested to investigate wear behavior, using Pin -on-Disc technique, by examining some variables of wear such as applied load, sliding speed, and sliding time. The results showed that wear rate increases with applied load and sliding time, while increasing the sliding speed and the percentage of SiC decreases the wear rate, as well as the alloy containing (12wt% SiC) showed better wear resistance compared with other alloys .

In this investigation ASTM 4118 steel was treated by using pulse Nd: YAG
laser with wave length 1064nm and pulse duration 100ns. In order to assess the
new tribological properties of laser surface hardened ASTM 4118 steel, the wear
resistance between specimens treated with laser and those of conventionally
hardened under dry sliding conditions was compared. The change of wear
mechanisms in laser hardened 4118 steel resulted in distinct difference in wear
rates.
The results showed that quenched zones not only had sufficient depth of
hardening and higher hardness, but had more retained austenite and finer carbides
because of a higher degree of carbide dissolution. Laser surface hardened ASTM
4118 steel specimens exhibited superior wear resistance to their conventionally
hardened specimens due to the change in the microstructure hardening, high
hardness. The wear mechanism for both the laser quenched layer and
conventionally hardened layer was highly similar, generally involving adhesive
wear mechanism , material transfer, wear induced oxidation and plowing. Also the
results of hardness show that increases with increasing of laser energy by 70%.

Metal samples such as Copper and Aluminum and alloy as Brass were prepared and machined as discs (plane sample) and as a half rings (curvature sample). The samples were polished by using metallographic paper with different grades. The micro roughness and the initial weight were measured for all samples before wear tests, and then the samples were subjected to wear testing system under lubricated condition, fixed normal load of 15N, sliding time 30 min and sliding speed of 750 rpm. During the running of wear testing system the temperature of the samples were measured .The wear rate was calculated by employing the weighing method. It is clear from the results that micro roughness values increasing leads to increase in weight loss , wear rate and the temperature of samples .The effect of sample shape on weight loss , wear rate and sample heat is also obvious when noticing that the different measurements of weight loss, wear rate and sample heat of curvature samples are higher than that of plane samples .

Metal matrix composite (MMCs) of the base alloy (Al-0.978%Mg-1.03%Si) reinforced
with SiC particles (10 wt %) with particle size (53-106) μm was prepared by stir casting
using vortex technique. Solution heat treatment and aging are carried out at a constant
temperature of 175C° for different aging times. Many inspections and tests such as
microstructure, Vickers hardness and XRD analysis. Wear test type ( Pin – on – Disc) with
various applied loads and different exposure times at constant parameters was carried out
under dry sliding conditions.
It was found that the addition of SiC particles to base alloy improved the hardness and
wear resistance before and after heat treatment (precipitation hardening).
In addition, using SiC particles with alloy matrix resulted in a faster aging response i.e the
time of peak hardness decreased from 8hr to 5hr for base alloy and composite respectively.
These results indicate that the addition of SiC particles to Al –alloy matrix accelerates the
aging kinetic.

This research involves using epoxy resin and (Nitride Butadiene Rubber
NBR) to form a blend with different resin ratios (90 – 10)%, (80 – 20)%,
(70 – 30)%, and (60 – 40)% to achieve better ratio for impact strength as a
function of better toughness; then reinforced with SiO2 and Al2O3 powders with
(20%) volume fraction. Mechanical properties were studied including impact
strength, wear resistance, and hardness before and after immersion in water and
HCl (0.5N).
Results showed that the composite (epoxy+NBR+SiO2) had better
properties compared with blend and Al2O3 composite. Also the acid solution had
affected then properties more than water. All impact and wear and hardness
decreased after immersing in solution.

This work investigates the effect of different media (0.1N of NaOH, H2SO4
and NaCl solution) on the polarization behavior of Al-Zn-Mg alloy and calculates
some of the corrosion parameters such as corrosion potential (Ecorr) and current
density (icorr), cathodic and anodic Tafel slopes (bc & ba), and the polarization
resistance (Rp) .
The results of the polarization resistance indicates that Al-Zn-Mg alloy have
resistance in slat solution higher than that observed in acidic and basic solution
respectively .
Also some of the mechanical properties like the hardness and wear were
measured. The results for hardness showed that the untreated alloy in the
experimental solutions had higher hardness than those which are treated in salt,
acidic , and basic solutions respectively .
While the results for the rate of wear at different sliding speeds showed that the
rate of wear for the samples that treated in basic solution higher than those for
samples which are treated in the acidic and salt solutions . Also the same results
were get when measure the rate of wear with different applying loads.

This work is concerned with a study of dry sliding wear of α–Brass (70/30) with
addition of lead and tin(3%wt) for each one alloy. Three brass alloys were prepared by
melting and pouring in steel molds. A Pin -on-Disc technique was used. The effect of
applied loads and sliding times on wear rate were examined. The results show that the
wear rate increases with increasing applied loads and with increasing sliding time at
constant sliding speed (2.7m/s) while hardness of steel disc was 35 HRc .
The results also show that the brass alloy containing 3% tin has more
wear resistance than that of other brass alloys.