Cr2O3 feedstock of nano and micron size particles were coated on low carbon steel by APS process. Ni-Al bond coat was used to improve the adhesion of coatings to substrate. Microstructural investigations were conducted by FESEM and X-ray diffractometery (XRD) was utilized for structural analysis. wear behavior of the coatings was studied by ball on disk testing using alumina balls at room temperature and 300 and 500oC under a load of 30N. Experimental results showed that both coatings consist of a layered structured of melted and semi-melted splats. However the nanostructured coating contained more semi-melted splats resulting more porosity compared to the microstructured coating. Tribological evaluation of the coatings revealed that the nanostructured coating exhibits lower friction coefficient in comparison to the microstructured Cr2O3 coating. wear rate of the coatings decreased by increasing the temperature so that at 300 and 500oC. The nanostructured coating presented better wear resistance. Improvement of wear resistance and decreasing the friction coefficient in nanostructured coating at different temperatures can be attributed to the effect of nanoparticles, Higher hardness and also formation of compacted and adhesive tribofilm on the surface of the coating.

Deep sub-zero treatment is a complementary operation performed on all types of tool steels, carbonized and High-speed steels to improve wear resistance and hardness. Among these tool steels, H13 is a hot work tool steel that have an extended application in industry as a hot deforming tool. This paper investigates the wear behavior of deep cryogenic treated H13 hot work steel at operating temperature. Two quench-tempered and quench-subzero-tempered samples are compared. The microstructures of the specimens were determined by scanning electron microscopy, and the structures were determined by X-ray diffraction. Vickers hardness used for determining hardness after each treatment. The wear test was carried out at 250° C (mold temperature on forging of copper base alloys). Finally, the wear surface was examined by scanning electron microscope equipped with EDS analyzer. The results show that the Highest hardness was in quench-subzero-tempered condition which is about 26% Higher than the quench-tempered in oil conditions. This is due to the formation of fine, dispersed and uniform precipitates and Higher martensite percentage in quench-subzero-tempered sample compared to quench-tempered sample. Quench-subzero-temper operation reduced the residual austenite percentage by 10% and improved the wear properties by 36% at 250° C. Examination of wear surfaces indicates the presence of oxidized surfaces adhered to the wear surface in the form of abrasive particles. These oxide levels were lower in quench-subzero-tempered sample than quench-tempered sample.

In this research, wear mechanisms and tribological properties of Ni-P and Ni-P-Ag electroless coatings at High temperatures have been studied. At First, the surface of carbon steel samples were prepared and then they were entered into the Nickel phosphorus electroless bath (with and without silver particles) to deposit Ni-P-Ag and Ni-P coatings on the substrates. After heat treatment at 400 ° C, the hardness of the coatings was measured using a microhardness tester and the tribological tests were implemented by Pin on disc method at 500 ° C. The microstructure of the coatings was also evaluated by XRD analysis and the surface morphology, cross-section and wear scars of the coatings were studied by using an optical microscope a scanning electron microscope equipped with EDS analyzer. The results showed that the co-deposition of silver particles in Ni-P coating led to the self-lubricating property as the result of the formation of silver rich tribofilms. It can be related to the diffusion of silver toward the sliding surface of Ni– P– Ag coating at High temperatures. Also, abrasive wear, surface oxidation and the plastic deformation were also recognized as the High temperature wear mechanisms in Ni-P-Ag coating.

Abstract Introduction: The thermal spraying method with the aim of increasing the working life of steel parts is one of the most important solutions in surface engineering to solve the problem of wear. Methods In this research, NiCrBSi and NiCrBSi-MoS2 coatings were applied on 304 stainless steel by thermal spraying, and then the wear behavior was evaluated at ambient temperature and 500 degrees. Phase investigations were done by X-ray diffraction test. The chemical composition of the coatings was checked with the help of energy dispersive spectrometer analysis. Porosity was investigated with the help of optical microscope and scanning electron microscope images. The hardness of the samples was measured using a microhardness test. In order to check the adhesion and tribological behavior of the coatings, VDI3198 and ASTM-G99 pin-on-disk tests were used, respectively, and finally, the wear mechanism was evaluated using SEM images and EDS analysis of the wear surfaces of the samples. Findings: Phase analysis (XRD) and chemical composition (EDS) showed that the coating has an amorphous and crystalline phase and the most important phases of the coating are nickel-gamma, carbide and boride. Porosity measurement results with the help of image analysis software showed Higher porosity of NiCrBSi-MoS2 coating. The results of hardness measurement from the cross-section of the samples indicated an increase in the hardness of the substrate in the presence of coatings, and the addition of MoS2 particles decreased the hardness of the NiCrBSi coating. The coating with MoS2 has better adhesive behavior due to its crystalline structure and better plastic deformation ability. The tribological results indicated the superiority of the NiCrBSi-MoS2 coating due to the appropriate ability of plastic deformation as well as the intrinsic lubrication property (based on the crystal structure) in this test. It was found that at ambient temperature, the samples mainly had lamellar wear mechanism, and at High temperature, oxidation wear as a secondary mechanism helped to destroy the surface. Conclusion: The addition of MoS2 to NiCrBSi coating caused more porosity, more roughness, less hardness and better wear behavior of the coating. The addition of MoS2 to the coating improved the wear resistance of the coating at High temperature.

In this research the effect of temperature and volume fraction of reinforcement on wear behavior of the Al/x vol% SiCp (x=0, 1, 3, 5) nanocomposite was investigated. Results revealed that addition of reinforcement particles increases transition to severe wear temperature of the samples, so that the temperature of transition to severe wear for the un-reinforced aluminum, Al-1%SiC, and Al-3%SiC and Al-5%SiC samples is 125oC, 150oC, and 175oC, respectively. Also, the composite samples showed lower wear rate and friction coefficient compared to the un-enforced aluminum, and with increase of volume fraction of SiC particles, wear resistance of the samples was improved. FESEM images from the surface of the samples worn at different temperatures revealed that wear mechanism in the mild wear area of all samples is the abrasive mode, but with increase of temperature and transition to severe wear area, wear mechanism of all samples except Al-5%SiC is the adhesive mode. The Al-5%SiC sample still shows the abrasive mode, which indicates the positive effect of the reinforcement phase.

This paper proposes a 2.4 GHz active mixer without passive inductor for the transceiver system. Taking into account the design requirements of the mixer, a double-balanced down-conversion structure with active inductor and negative resistance is designed. The proposed mixer with 130 nm CMOS technology is designed and simulated using Cadence software at 1.5 V supply voltage. Although we had to compromise conversion gain with linearity, we were able to achieve very High conversion gain with average linearity. Based on the results of post-layout simulations, the conversion gain of 27.57 dB, IIP3 equal to -7.88 dBm, 1-dB compression point equal to -17.34 dBm and IIP2 equal to 44.22 dBm with power consumption of 2.5 mW was obtained for the proposed mixer. The chip size without input and output pads is 95.18 µm × 117.68 µm, which leads to a chip area of 0.0112mm2.