Iranian Journal of Materials Science and Engineering

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This paper aims to study the tribological and electrochemical properties of the CrN/AlCrN nano-layer deposited on H13 tool steel. Arc physical technique was employed to deposit multilayer coating. X-ray diffraction technique, thermionic and field emission scanning electron microscopy and energy dispersive spectroscopy have been used to determine the characteristics of the samples. To study the samples' wear behavior, coating adhesion, and surface hardness, reciprocating wear test, Rockwell-C test, and microhardness Vickers tester were employed, respectively. The measured values of the coefficient of friction and the calculated wear rates showed that the CrN/AlCrN multilayer coating has a much higher wear resistance than the uncoated sample. The coefficient of the friction of the coated sample was 0.53 and that of the uncoated sample was 0.78. Moreover, the wear rate of the coated H13 steel was about 127 times lower than the bare H13 steel sample. The results obtained from electrochemical impedance spectroscopy and polarization tests demonstrated that the corrosion current density of the H13 steel sample was 8 μA/cm2 and that of the CrN/AlCrN multilayer-coated sample was 3 μA/cm2. In addition, the polarization resistance of the treated and the substrate specimens was estimated at 4.2 and 2.7 kΩ.cm2, respectively.

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In the present research work physical, mechanical and tribological behavior of Aluminum (Al) alloy LM13 reinforced with Nano-sized Titanium Dioxide (TiO₂) particulates were fabricated, mechanical and tribological properties were investigated. The amount of nano TiO₂ particulates in the composite was added from 0.5% to 2% in 0.5 weight percent (wt %) increments. The Al-LM13-TiO₂ Metal Matrix Composites (MMCs) were prepared through the liquid metallurgical method by following the stir casting process. The different types of Al LM13-TiO₂ specimens were prepared for conduction of Physical, Mechanical, and Tribological characteristics by ASTM standards. Microstructural images, hardness, tensile, and wear test results were used to evaluate the effect of TiO₂ addition to Al LM13. Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), and X-Ray Diffractometer (XRD) were used to examine the microstructure and distribution of particulates in the matrix alloy. In the Al LM13 matrix, microstructure analysis indicates a consistent distribution of reinforced nanoparticles. The attributes of the MMCs, including density, hardness, tensile strength, and wear resistance, were improved by adding up to 1 wt% TiO₂. Fractured surfaces of tensile test specimens were studied using SEM pictures.  The standard pin-on-disc tribometer device was used to conduct the wear experiments; the tribological characteristics of unreinforced matrix and TiO₂ reinforced composites were investigated. The composites’ wear resistance was increased by adding up to 1 wt% of TiO₂.  The wear height loss of Al LM13-TiO₂ composite increased when the sliding distance and applied load were increased. Overall, the Al LM13 with one wt% of TiO₂ MMCs showed excellent Physical, Mechanical and Tribological characteristics among all the percentages considered in the present study.

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Pressureless sintering was employed at 1400 °C to synthesize Ti matrix composites (TMCs) reinforced with in-situ TiB and TiC reinforcements using TiB₂ and B₄C initial reinforcements. The microstructure and wear behavior of the synthesized composites were evaluated and compared and the results showed that B₄C caused the formation of TiB-TiC in-situ hybrid reinforcements in the Ti matrix. Also, TiB was in the form of blades/needles and whiskers, and TiC was almost equiaxed. Moreover, the volume fraction of the in-situ formed reinforcement using B₄C was much higher than that formed using TiB₂. In addition, although the hardness of the B₄C-synthesized composites was higher, the composite synthesized using 3 wt.% TiB₂ exhibited the highest hardness (425 HV). The wear test results showed that the sample synthesized using 3 wt.% TiB₂ showed the lowest wear rate at 50 N, mainly because of its higher hardness. The dominant wear mechanism in the samples synthesized using 3 wt.% B₄C was abrasive and delamination at 50 N and 100 N, respectively while in the samples synthesized 3 wt.% TiB₂, a combination of delamination and adhesive wear and adhesive wear was ruling, respectively.