Tribological properties and wear prediction model of TiC particles reinforced Ni-base alloy composite coatings

TiC particles reinforced Ni-based alloy composite coatings were prepared on 7005 aluminum alloy by plasma spray. The effects of load, speed and temperature on the tribological behavior and mechanisms of the composite coatings under dry friction were researched. The wear prediction model of the composite coatings was established based on the least square support vector machine (LS-SVM). The results show that the composite coatings exhibit smaller friction coefficients and wear losses than the Ni-based alloy coatings under different friction conditions. The predicting time of the LS-SVM model is only 12.93%of that of the BP-ANN model, and the predicting accuracies on friction coefficients and wear losses of the former are increased by 58.74%and 41.87%compared with the latter. The LS-SVM model can effectively predict the tribological behavior of the TiCP/Ni-base alloy composite coatings under dry friction.

Friction behavior of Ti-30Fe composites strengthened by TiC particles

Ti-Fe-x TiC(x=0, 3, 6, 9, wt.%) composites were fabricated through low temperature ball milling of Ti, Fe and TiC powders, followed by spark plasma sintering. The results show that β-Ti, β-Ti-Fe, η-Ti4 Fe2 O0.4 and TiC particles can be found in the composites. The microstructure can be obviously refined with increasing the content of TiC particles. The coefficient of friction(COF) decreases and the hardness increases with increasing the content of TiC particles. The adhesive wear is the dominant wear mechanism of all the Ti-Fe-x TiC composites. The Ti-Fe-6 TiC composite shows the best wear resistance, owing to the small size and high content of TiC particle as well as relatively fine microstructure. The wear rate of the Ti-Fe-6 TiC composite is as low as 1.869× 10-5 mm3/(N·m) and the COF is only 0.64. Therefore, TiC particle reinforced Ti-Fe based composites may be utilized as potential wear resistant materials.

Fabrication of cast carbon steel with ultrafine TiC particles

The carbon steels dispersed with ultrafine TiC particles were fabricated by conventional casting method. The casting process is more economical than other available routes for metal matrix composite production, and the large sized components to be fabricated in short processing time. However, it is extremely difficult to obtain uniform dispersion of ultrafine ceramic particles in liquid metals due to the poor wettability and the specific gravity difference between the ceramic particle and metal matrix. In order to solve these problems, the mechanical milling (MM) and surface-active processes were introduced. As a result, Cu coated ultrafine TiC powders made by MM process using high energy ball milling machine were mixed with Sn powders as a surfactant to get better wettability by lowering the surface tension of carbon steel melt. The microstructural investigations by OM show that ultrafine TiC particles are distributed uniformly in carbon steel matrix. The grain sizes of the cast matrix with ultrafine TiC particles are much smaller than those without ultrafine TiC particles. This is probably due to the fact that TiC particles act as nucleation sites during solidification. The wear resistance of cast carbon steel composites added with MMed TiC/Cu-Sn powders is improved due to grain size refinement.

Microstructure and wear properties of the electroslag remelting layer reinforced by TiC particles

The electroslag remelting （ESR） layer reinforced by TiC particles was obtained by electroslag remelting. The microstructure and wear properties of the ESR layer were studied by means of scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and wear test. The results indicate that TiC particles are synthesized by self-propagating high-temperature synthesis （SHS） reaction during the electroslag remelting process. The size of TiC particles is in the range of 1-10 μm, and the distribution of TiC particles is uniform, from outside to inside of the ESR layer, and the volume fraction and the size of TiC particles decrease gradually. Molten iron and slag flow into porosity due to the SHS process leading to rapid densification and the elimination of porosity in the ESR layer during the ESR process. TiC particles enhance the wear resistance of the ESR layer, whereas CaF2 can improve the high temperature lubricating property of the ESR layer.

Friction and wear behavior of TiC particle reinforced ZA43 matrix composites

TiC/ZA43 composites were fabricated by XD TM and stirring casting techniques. The tribology properties of the unreinforced ZA43 alloy and the composites were studied by using a block on ring apparatus. Experimental results show that the incorporation of TiC particles improves the microstructure of ZA43 matrix alloy. The coefficient of friction μ and the width of worn groove decrease with the increase of TiC volume fraction φ (TiC). The width of worn groove and μ of the composite during wear testing increase with increasing the applied load. Metallographic examinations reveal that unreinforced ZA43 alloy has deep ploughing grooves with obvious adhesion phenomenon, whereas TiC/ZA43 composites have smooth worn surface. Delamination formation is related to the fatigue cracks and the shear cracks on the surface. [

The Synthesis of TiNi and Composite Particles in Molten Salts

A novel process for synthesizing TiNi and TiNi/TiC particles, called the high-temperature salt-melting method, is discussed in this paper. So far as this method is concerned, the molten salts are a reaction medium that does not take part in the chemical reaction but can be easily dissolved by water washing. With this method, TiNi shape memory alloy and TiNi/TiC composite particles were prepared in molten salts at 680-850℃. TiNi particles, ranging from 100 nm to several microns in diameter, are obtained and the reverse martensitic transformation is confirmed in these particles by the differential scanning calorimetry （DSC）. The reaction temperature and the holding time have no significant influence on the particle size, morphology or the reverse martensitic transformation characteristics. In the molten salts, the released heat of the chemical reaction causes the local temperature to rise quickly, which is the key to obtaining the desired particulate composite.

Synergistic effects of multiscale TiC and dual-phase structure on tensile properties of particle-reinforced steel

The conventional melting methods were used to obtain in situ TiC particle-reinforced dual-phase steel,followed by hot rolling and heat treatment processes.The aim was to investigate the effect of TiC particles on the fracture behavior of dual-phase steel at different annealing temperatures,by analyzing the microstructure and tensile behavior of the multiscale TiC particle-reinforced dual-phase steel.The results showed that TiC particles precipitated in the as-cast microstructure of dual-phase steel were distributed along the grain boundaries.During hot rolling,the grain boundary-like morphology of the micron-sized TiC particles was disrupted,and the particles became more refined and evenly distributed in the matrix.The tensile tests revealed that the strength of the TiC particle-reinforced dual-phase steel increased with increasing martensite content,while the elongation decreased.These results were similar to those of conventional steel.The addition of 1 vol.%multiscale TiC particles improved the strength of the dual-phase steel but did not affect elongation of the steel.Cracks and holes were primarily concentrated around the TiC particles rather than at the interface of martensite and ferrite.The main causes of crack sprouting were TiC particle interface cracking and TiC particle internal fragmentation.Overall,the study demonstrated the potential of multiscale TiC particle-reinforced dual-phase steel as a strong and tough material.The refined distribution of TiC particles in the matrix improved the strength of the material without compromising its elongation.The results also highlighted the importance of careful selection of reinforcement particles to avoid detrimental effects on the fracture behavior of the material.

In-situ TiC Reinforced Composite Coating Produced by Powder Feeding Laser Cladding

A Ni-base alloy composite coating reinforced with TiC particles of various shapes and sizes on medium carbon steel substrate was produced by multilayer laser cladding. The chemical compositions, microstructures and surface morphology of the cladded layer were analyzed using energy dispersive X-ray spectroscopy （EDX）, scanning electron microscope （SEM）, and X-ray diffractometry （XRD）. The experimental results showed that an excellent metallurgical bonding between the coating and the substrate was obtained. The microstructure of the coating was mainly composed of γ-Ni dendrites, a small amount of CrB, Ni3B, M23C6 and dispersed TiC particles. Much more and larger TiC particles formed in the overlapping zone, which led to a slightly higher microhardness of this zone. The maximum microhardness of the coating was about HV0.21200. The effects of the laser processing parameters on the microstructures and properties of coating were also investigated.

Microstructure and mechanical properties of Al-TiB_2/TiC in situ composites improved via hot rolling

A kind of Al-TiB2/TiC in situ composite with a homogenous microstructure was successfully prepared through in situ reaction of pure Ti and Al-B-C alloy with molten aluminum.In order to improve the distribution of the particles and mechanical properties of the composites,subsequent hot rolling with increasing reduction was carried out.The microstructure evolution of the composites was characterized using field emission scanning electron microscopy(FESEM)and the mechanical properties were studied through tensile tests and microhardness measurement.It is found that both the microstructure uniformity and mechanical properties of the composites are significantly improved with increasing rolling reduction.The ultimate tensile strength and microhardness of the composites with90%rolling reduction reach185.9MPa and HV59.8,respectively,140%and35%higher than those of as-cast ones.Furthermore,the strengthening mechanism of the composite was analyzed based on the fracture morphologies.

Microstructures and Mechanical Properties of TiC_P/Al-4.5Cu-0.8Mg Composites by Direct Reaction Synthesis

Direct reaction synthesis (DRS), based on the principle of self-propagating high-temperature synthesis (SHS), is a new method for preparing participate metal matrix composites. TiCP/AI-4.5Cu-0.8Mg composites were fabricated by DRS. Participate composites were fabricated with Ti carbide (TiC) particles, generally less than 1.0μm. The reacted, thermal extruded samples exhibit a homogeneous distribution of fine TiC particles in AI-4.5Cu-0.8Mg matrix. Mechanical property evaluation of the composites has revealed a very high tensile strength relative to the matrix alloy. Fractographic analysis indicates ductile failure.

Fabrication of in-situ TiC reinforced composite coating via plasma transferred arc process

In this work, the in-situ TiC panicles reinforced composite coating was prepared by plasma transferred arc process on the surface of Q235 steel. Microstructures, phase composition and wear property of the coating were investigated. The results showed that the composite coating consisted mainly of T-Ni, TiC, Cr23C6, Cr7C3, Ni3Si, CrB, Cr5B3 and FeNi3 phases, and was characterized by fine TiC panicles embedded in Ni matrix. The wear resistance of composite coating was significantly improved compared with that of the steel substrate. The wear volume loss of the substrate was 443 mm3, which was about 9 times as that of in-situ TiC particles reinforced composite coating （49 mm3 ）. It is mainly attributed to the presence of chromium carbide particles and in-situ TiC particles and their favorable combination with Ni matrix.

Isothermal grain growth of reactive spray formed 7075 alloys in semi-solid state

The grain growth behavior in reactive spray formed 7075+2.91 vol percent TiCAl alloy was studied and compared with that of spray formed 7075 Al alloy at semi-solid state. Theeffects of in-situ TiC particles on the microstructure of spray formed 7075 Al alloy were alsoinvestigated. The specimens were heat-treated isothermally at various temperatures between thesolidus and liquidus of 7075 Al alloy for times in the range of 10-60 min, then quenched in water.The microstructure of reheated specimens was characterized using scanning electron microscopy andoptical microscopy. The grain size was measured using a mean linear intercept method. Results showthat the in-situ TiC particles can effectively retard grain growth and refine the grain at a limitedsize. The grain growth exponent in Arrhenius equation increases from 2 to 3, which indicates thatthe in-situ TiC particles have the significant pinning effect on grain coarsening in the semi-solidstate.

In Situ TiC/FeCrNiCu High-Entropy Alloy Matrix Composites:Reaction Mechanism,Microstructure and Mechanical Properties

In situ TiC particles-reinforced FeCrNiCu high-entropy alloy matrix composites were prepared by vacuum induction melting method.The reaction mechanisms of the mixed powder(Ti,Cu and C)were analyzed,and the mechanical properties of resultant composites were determined.Cu4Tiwere formed in the reaction of Cu and Ti when the temperature rose to 1160 K.With the temperature further increased to 1182 K,newly formed Cu4Tireacted with C to give rise to TiC particles as reinforcement agents.The apparent activation energy for these two reactions was calculated to be 578.7 kJ/mol and 1443.2 kJ/mol,respectively.The hardness,tensile yield strength and ultimate tensile strength of the 15 vol%TiC/FeCrNiCu composite are 797.3 HV,605.1 MPa and 769.2 MPa,respectively,representing an increase by 126.9%,65.9%and 36.0%as compared to the FeCrNiCu high-entropy base alloy at room temperature.However,the elongation-to-failure is reduced from 21.5 to 6.1%with the formation of TiC particles.It was revealed that Orowan mechanism,dislocation strengthening and load-bearing effect are key factors responsible for a marked increase in the hardness and strength of the high-entropy alloy matrix composites.

Interfacial characteristics in CNTs-AgCuTi systems

AgCuTi-based composite fillers reinforced with Carbon Nanotubes(CNTs) were prepared by mechanical ball milling and ultrasonic agitation. The morphological features, chemical components, and melting characteristics of the composite fillers with different content of CNTs addition were investigated using Field Emission Scanning Electron Microscopy(FESEM), XRay Diffraction(XRD) and a Differential Scanning Calorimeter(DSC). After being heated at 900 ℃, the microstructure of the composite fillers was examined through FESEM and Transmission Electron Microscopy(TEM) to analyze the interfacial characteristics in the AgCuTi-CNTs system.The microstructures of the composite fillers with 0.5 wt% CNTs and 0.1 wt% CNTs were compared. It was found that 0.5 wt% CNTs were favorable for dispersive distribution of the structure.Nano-sized TiC particles formed in the reaction of CNTs with Ti, resulting in the transformation of TiCu;with high Ti content and Ti;Cu;phases to TiCu;phase with low Ti content. Additionally,the microstructure evolution of the composite fillers was studied by changing the ratio of Ti/CNTs.Results showed that CNTs significantly influenced the wettability of the AgCuTi filler. After addition of 0.3 wt% of CNTs, the spreading area of the composite filler on the C/C composite increased by 146.0%.

Friction and wear behavior of Cu-4 wt.％Ni-TiC composites under dry sliding conditions

The present study synthesized Cu-4 wt％ Ni matrix composites reinforced with different percentages of TiC (0,2,4,6,and 8 wt％) through high-energy ball milling,followed by compaction and sintering.The friction and wear behavior was examined at four different normal loads of 5,10,15,and 20 N.A constant sliding speed of 1.25 m/s was maintained while sliding against a hardened counterface made of EN31 steel (HRC 60) under ambient conditions using a pin-on-disk test rig.The composite hardness increased until the addition of 4 wt％ of TiC,beyond which it was observed to decrease.Such a trend may be attributed to the TiC agglomeration in the composites containing relatively larger amounts of TiC (i.e.,6 and 8 wt％).The wear rate linearly increased with the load.However,the composites exhibited a lower rate of wear than the matrix alloy,which may have resulted from the relatively higher hardness of composites.The observed friction and wear behavior has been explained on the basis of hardness and presence of the transfer layer on the worn surface and its nature,i.e.,loose or well compacted.Addition of 4 wt％ TiC showed the optimum performance in terms of friction and wear caused by its higher hardness and ability to hold a transfer layer of a relatively larger thickness compared to the other materials.The wear mechanism for the Cu4Ni matrix alloy was a mix of adhesive and oxidative wear and primarily abrasive for the composites containing hard TiC particles.