Papers by Keyword: Surface Composite

Abstract: In this investigation, copper (Cu) based surface composites reinforced with silicon carbide (SiC) particles were fabricated using friction stir processing (FSP) route. FSP was carried out considering three-factor three-level Box-Behnken design to study the effects of process parameters on peak temperature and hardness of Cu/SiC_p surface composites. Microstructural evaluation using optical microscope (OM) revealed that SiC_p were uniformly distributed and well – bonded with copper matrix at an adequate heat input conditions. The microhardness of the surface composites were remarkably enhanced than that of base metal. Regression models have been developed for predicting peak temperature and microhardness of processed surface composites and the same were in good agreement with experimental results.

Abstract: Friction stir processing (FSP) is a novel technique used to fabricate surface composites. This investigation is an attempt to made Al/Al₂O₃ and Al/SiC surface composite using FSP and compare the mechanical and metallurgical properties influenced by the types of reinforcement particles. Two plates were grooved with 0.8 mm in width, 5 mm in depth and 100 mm in length in the middle of the aluminium plate using wire EDM and compacted with Al₂O₃ and SiC powder. The FSP was carried out automatically on an indigenously built FSW machine at tool rotational speed of 1200 rpm, processing speed of 60 mm/min and axial force of 10 kN. The optical and Scanning Electron microstructures are precisely revealed the homogeneous distribution of Al₂O₃ and SiC particles in the stir zone of surface composite layer (SCL). The microhardness was measured across the cross section of SCL layers of Aluminium and Aluminium with SiC and Al₂O₃. The higher microhardness was obtained in Aluminium with SiC and Al₂O₃ composites fabricated by FSP. This is because of the higher hardness value of SiC particles than Al₂O₃ particles.

Abstract: An attempt is made to mitigate wear in cast magnesium alloy by incorporating flyash reinforcement on the surface through friction stir processing. Wear resistance is evaluated using pin-on-disc wear testing. Effect of dry sliding wear process parameters such as speed, time and distance were studied by using design of experiments. Empirical relationships were established between the process parameters and wear resistance of base metal as well as surface composite. Further, wear map is constructed using graphical optimization technique, which can be used to predict the lower and upper bound of wear rate for the both base metal and friction stir processed surface composites under dry sliding condition.

Abstract: The AlN particles reinforced composite was fabricated on the surface of aluminum 6061-T6 alloy rolled plate by five passes friction stir processing (FSP). Microstructure of FSPed sample was characterized by optical microscope and scanning electron microscope. AlN particles in composite were verified by EDS and XRD. Microhardness and resistance to wear were also investigated. Results show that grains in composite were refined by dynamic recrystallization and uniformly dispersed AlN particles. Composite region bonded with the Al substrate well. No reaction occurred at the interface between AlN and Al matrix. By comparison with base metal, the FSP-produced composite exhibited improved microhardness and substantial wear weight loss reduction.

Abstract: WC-Co surface reinforced composite was formed by V-EPC (vacuum-expendable pattern casting), and the microstructure of the matrix in the composite was investigated. The results show that the Co addition caused the appearance of granular pearlite and troostite in the matrix, therefore the brittle tendency of the composite was lighten. After the molten steel infiltrating into the preform, the component diffusion in matrix decreased from the substrate to the surface of composite, the composition of the matrix became more uneven, and the formation of the granular pearlite and troostite were facilitated. When the atomic concentration of W and C in the matrix increased, Co₃W₃C, η type carbide, was easier to separate out. Before the temperature of the composite drop to 1200°C, Co₃W₃C could precipitate in the interface reaction between the matrix and the tungsten carbide particles, the hardness of the matrix would be increased, and then the abrasive resistance of the composite could be improved.

Abstract: In order to optimize the processing parameters of TiC/steel composite materials, in-situ TiC particle reinforced steel-based surface composites were prepared by vacuum evaporative pattern casting (V-EPC) infiltration process, and the structure and interface of the composites were investigated. The results show that, TiC particle size with Ti-C-20wt%Fe reaction system was much smaller than the composite with Ti-C reaction system in the same location of the composites. In the composites, the TiC particle size and volume fraction increased and spherical degree dropped from the tradition layers (interface between the substrate and the composite layer) to the outer surface. But the increase of TiC particle size (1-3μm) and volume fractions (25.8%-43.5%) in the composite with Ti-C-20wt%Fe reaction system was obviously lower than that of TiC particle size (1-10μm) and volume fractions (12.3%- 67.7%) in the composite with Ti-C reaction system. The bond zone between TiC particles and the matrices was totally metallurgical bonding without apparent interface. Comparing with the composite with Ti-C-xFe reaction system, the tradition layer with Ti-C reaction system has a poorer internal quality. The forming process of TiC in situ synthesized reinforced steel substrate surface composites prepared by V-EPC infiltrating process was infiltrating of the melting and carbothermal reactions of C and Ti powder the result of joint action.

Abstract: The slurry erosion wear performances of the SiC_p/cast iron surface composite, which was prepared by infiltrating molten cast iron into SiC particles preforms, were studied on self-made slurry inject erosion wear machine. The results show that the erosion wear rate of the SiC_p/cast iron surface composite would be the lowest at impact angle of 30°, and the largest at impact angle of 60°. The erosion wear rate increases gradually when impact angle is changed from 30° to 60°, and then decreased with increasing the impact angle. The erosion wear mechanism of the SiCp/cast iron surface composite is dominated by cutting and grooving at low impact angle, and by fatigue spalling and cutting at high impact angle. For the gray cast iron, the erosion wear rate of would be increased gradually with the increase of impact angle, reaching the peak value at 90°, which indicates the typical characteristics of brittle material in slurry erosion wear process.

Abstract: A wear resistant TiC-Cr₇C₃ /Fe surface composite was produced by cast technique and in-situ synthesis technique. The microstructure and dry-sliding wear behavior of the surface composite was investigated using scanning electron microscope(SEM), X-ray diffraction(XRD) and MM-200 wear test machine. The results show that the surface composite consists of TiC and Cr₇C₃ as the reinforcing phase, α-Fe and γ-Fe as the matrix. The surface composite has excellent wear-resistance under dry-sliding wear test condition with heavy loads.

Abstract: The present study is concerned with the improvement of hardness and wear resistance in (Cr3C2,CrB)/carbon steel surface composites fabricated by high-energy electron beam irradiation. Two kinds of powder mixtures, 50Cr3C2-50STS304 and 50CrB-50STS304 (wt.%), were placed on a plain carbon steel substrate, which was then irradiated with electron beam. The surface composite layer of 1.0~1.3 mm in thickness was successfully formed without defects, and contained a large amount (up to 58 vol.%) of Cr7C3 or Cr1.65Fe0.35B0.9 particles in the austenite or martensite matrix. The hardness and wear resistance of the surface composites were 2~3 times higher than those of the steel substrate according to hard particles. Particularly, the surface composite fabricated with CrB powders showed excellent wear resistance because selective wear of the matrix was considerably reduced.

Abstract: This study aims at correlating microstructure with hardness and corrosion resistance of surface alloyed materials fabricated with Fe-based metamorphic powders by an accelerated electron beam irradiation method. The surface alloyed materials contained 48 vol.% of hard Cr2B crystalline phases in the Cr0.19Fe0.7Ni0.11 matrix, and thus its hardness was 2.5 times greater than that of the steel substrate. The corrosion resistance of the surface alloyed materials was better than that of an STS304 stainless steel or coatings fabricated by high-velocity oxygen fuel spraying of Fe-based metamorphic powders because the Cr0.19Fe0.7Ni0.11 matrix of the surface alloyed layers and coating was selectively corroded, while Cr2B borides were retained inside pits. These findings suggested that the fabricated surface alloyed materials presented good application possibilities as excellent wear- and corrosion-resistant materials.