Ultra wear resistant TiC-Fe coating prepared by high efficient and economic plasma cladding method

The key components of engineering machinery frequently failed due to working in the high load and high wear operating envir-onment.And the performance of the Fe-based alloy coatings typically employed need to be improved for fulfilling the service requirements.Herein,a TiC strengthened Fe-based alloy cladding layer,named TiC-Fe coating,was designed and prepared by plasma cladding technology.The frictional wear performance of coating under various loads was tested.The wear morphology of the coating was observed,and its wear mechanism was examined.The results indicated that the TiC-Fe coating was well formed and metallurgically bonded to the Q345C substrate.Its microstructure mainly consisted of Fe-Cr solid solution,α-Fe phase,(Fe,Cr)_(7)C_(3) phase and TiC phase.The coating exhibited an average microhardness of 980 HV0.2,which was about 5.4 times that of the Q345C substrate.The wear mass loss of the TiC-Fe coatings was much smaller than that of the Q345C substrate,which indicated that the wear resistance of the Q345C coating was superior to the substrate,and the wear mechanism of the coating was mainly attributed to the abrasive wear.

Effect of Hot Deformation on Formation and Growth of Thermal Fatigue Crackin Chromium Wear Resistant Cast Iron

The formation and growth of thermal fatigue crack in chromium wear resistant cast iron was investigated, and the effect of hot deformation on the crack was analyzed by means of optical microscope and scanning electron microscope and high frequency induction thermal fatigue tester. The results show that eutectic carbide is the main location and passage for initiation and extension of thermal fatigue cracks, hot deformation can improve the eutectic carbiders morphology and distribution, inhibit the generation and propagation of thermal fatigue cracks. In the experiment, the propagation rate of thermal fatigue crack reduces with the quantity of hot deformation increasing, which was analyzed in the point view of the activation energy of crack propagation.

Preparation of Wear Resistant Materials by Melting and Diffusion Process

A wear-resistant material reinforced with VCp was manufactured by the in-mold melting process, in which the high-vanadium alloy-rods were melted by high temperature liquid steel and elements diffused into the liquid. Microstructure of the material was examined by OM, SEM, and XRD, and alloy elements in the diffusion layer were studied by EDS, and the hardness of the material was tested by HRS. The experimental results show that the material gradually changes hardness, which is due to the uniformly existents of carbide particles on martensite matrix and the gradient distribution of vanadium and carbide.

Formation and Growth of Granular Carbides in Multiple Alloying Wear Resistant Cast Iron Containing RE Through Hot Deformation

The granular carbides formed from hot deformation in multiple alloying wear resistant cast iron were studied through the observation by means of optical microscope, SEM and TEM. The experimental results show that carbides with large size are formed from original short rhabdoid carbides existing in cast, those with small size directly nucleate in the matrix. Carbides with the size between the above are formed from precipitation induced by hot deformation. The bigger the deformation is, the larger the number of microsized granular carbides is. The mechanisms of nucleation and growth of granular carbides and the function of RE were discussed.

Influence of Rare Earth on Wear Resistance of Wear Resistant Cast Iron Containing Low Alloy

The Influence of RE on wear resistance of wear resistant cast iron containing low alloy was studied by means of slide wear and impact wear test. Moreover, its microstructure and characteristics of wearing surface was analyzed. The experimental results show that RE can improve the wear resistance of wear resistant cast iron containing low alloy, especially for impact wear resistance. The optimum wear resistance of wear resistant cast iron containing low alloy modified by RE of 0.046% can be obtained by normalization at 950 ℃ for 3 h. Moreover, the coordinated effect of rare earths and heat treatment was also revealed in this paper.

A new production technique for wear resistant ring-hammers

Based on a great number of laboratory experiments, a new technique has been developed for producing wear resistant ring-hammers. In this technology, lost foam casting with iron sand was combined to make mold; a special alloy was used to inoculate the molten steel, and proper heat treatment was used to further improve mechanical properties of wear resistant ring-hammers. The influence of this new production technology on the microstructure and mechanical properties of wear resistant ring-hammers was studied. Results show that iron sand molding, having the inherent characteristic of sand molding, changes the type of metallic compounds, refines crystal grains and increases the fineness of microstructure. Practical experience verified that the properties of the ring-hammers produced with this new technique are as follows: tensile strength (Rm) 720 MPa, impact toughness (ak) > 210 J·cm-2 and hardness > 200 HB. After water quenching from 1,080℃ (holding for 4 h) and tempering at 320℃ for 3 h, the best wear resistance is obtained, and the wear resistance is 1.6 times higher than that of common high manganese ring-hammers.

Research and Application of Wear Resistant Refractories for Cooling Zone of Large Scale Coke Dry Quenching Ovens

In order to prolong the service life of the cooling zone of large scale coke dry quenching ovens,six kinds possible refractories for the cooling zone of large scale coke dry quenching ovens： SiC containing brick A,SiC containing brick B,mullite-andalusite brick,spinel containing brick,zirconia containing brick,corundum-mullite brick and grade B mullite brick,were analyzed in properties. It is found that the cooling zone lining adopting SiC containing bricks or mullite-andalusite bricks has much longer service life. Based on this,a new type of wear resistant brick was developed. The brick has a compressive strength of 135 MPa,a wear loss of 2. 10cm^3（only a quarter of that of the grade B mullite brick）,and a higher bulk density than the grade B mullite brick. The application of the brick in a 140t·h^（-1）coke dry quenching oven showed that it performed better than the grade B mullite brick. The cooling zone adopting the new bricks has a lower coke discharging temperature,which is beneficial to the enhancement of heat recovery efficiency and steam power generation.

Effect of RE Modification and Heat Treatment on Impact Fatigue Property of a Wear Resistant White Cast Iron

The morphology of carbides, as well as the generation and propagation of fatigue cracks in a wear resistant white cast iron after impact fatigue test were observed by means of optical microscope and SEM, and the relationship among the content of RE (rare earths) in the wear resistant white cast iron and the heating temperature as well as the length and propagation speed of the fatigue cracks were determined. Based on the obtained results, the effect of RE modification and heat treatment on the impact fatigue property was further studied. Experimental results show that addition of RE can defer the time required for the generation of fatigue cracks, reduce their propagation speed and increase the impact fatigue resistance. The aforesaid effect is more noticeable in case of combined RE modification with heat treatment, which can be attributed to the variation in morphology and the distribution of the eutectic carbide network.

Effect of Rare Earths on Microstructure and Properties of TiC-based Cermet/Cu Alloy Composite Wear Resistant Materials

The effect of rare earth (RE) oxide on the microstructure and properties of TiC based cermet/Cu alloy composite hardfacing materials was investigated by using scanning electron microscope (SEM), transmission electron microscope (TEM), impact test and wear test. The mechanism of RE oxide for improving the phase structure and the impact toughness was also discussed. The experimental results indicate that the microstructure of the matrix can be refined, and the micro-porous defects can be eliminated by adding RE oxide into the composite materials. The polycrystalline and amorphous phase structure is formed at the interface of cermet and matrix metal. The formed structure enhances the conjoint strength of interface. The frictional wear resistance can be improved obviously, although the microhardness of the matrix metal can not be effectively increased by adding RE oxide.

Microstructure and properties of a wear resistant Al-25Si-4Cu-1Mg coating prepared by supersonic plasma spraying

A high content silicon aluminum alloy(Al-25Si-4Cu-1Mg)coating was prepared on a 2A12 aluminum alloy by supersonic plasma spraying.The morphology and microstructure of the coating were observed and analyzed.The hardness,elastic modulus,and bonding strength of the coating were measured.The wear resistance of the coating and 2A12 aluminum alloy was studied by friction and wear test.The results indicated that the coating was compact and the porosity was only 1.5%.The phase of the coating was mainly composed ofα-Al andβ-Si as well as some hard particles(Al9Si,Al3.21Si0.47,and CuAl2).The average microhardness of the coating was HV 242,which was greater than that of 2A12 aluminum alloy(HV 110).The wear resistance of the coating was superior to 2A12 aluminum alloy.The wear mechanism of the 2A12 aluminum alloy was primarily adhesive wear,while that of the coating was primarily abrasive wear.Therefore,it is possible to prepare a high content silicon aluminum alloy coating with good wear resistance on an aluminum alloy by supersonic plasma spraying.

Dry wear behaviors of wear resistant composite coatings produced by laser cladding

Using different proportional mixtures of Ni-coated MoS_2, TiC and pure Nipowders, new typical wear resistant and self-lubricant coatings were formed on low carbon steel bylaser cladding process. The microstractures and phase composition of the composite coatings werestudied by SEM and XRD. The typical microstructure of the composite coating is composed ofmulti-sulfide phases including binary element sulfide and ternary element sulfide, gamma-Ni, TiC andMo_2C. Wear tests were carried out using an FALEX-6 type pin-on-disc machine. The frictioncoefficient and mass loss of three kinds of MoS_2/TiC/Ni laser clad coatings are lower than those ofquenched 45 steel, and the worn surfaces of the laser cladding coatings are very smooth. Because ofhigh hardness combined with low friction, the laser cladding composite coating with a mixture of 70percent Ni-coated MoS_2, 20 percent TiC and 10 percent pure Ni powder presents better wearbehaviors than the composite coating with other powder blends. The composition analysis of the wornsurface of GCrlS bearing steel shows that the transferred film from the laser cladding coating tothe opposite surface of GCrl5 bearing steel contains an amount of sulfide, which can change themicro-friction mechanism and lead to a reduced friction coefficient.

Influence of RE on Carbide Morphology and Mechanical Property of Wear Resistant White Cast Iron

The influence of rare earths content on carbide morphology and mechanical properties of wear resistance of white cast iron was studied by means of metallographic examination,scanning electron microscopic examination and mechanical property test. The experiment results show that RE can change carbides from continuous network to isolated particles and improve the mechanical properties,especially in combination with proper heat treatment. The optimum properties of wear resistance of white cast iron modified by RE of 0.045% can be obtained by normalization at 960 ℃ for 2 h.

Effect of RE Modification and Heat Treatment on Formation and Growth of Thermal Fatigue Crack in Wear Resistant Cast Iron Containing Low Alloy

The formation and growth of thermal fatigue crack and the function of RE and heat treatment in wear resistance of cast iron containing low alloy were investigated,and it was analyzed in view of the activation energy for the crack′s propagation. The results show that the thermal fatigue cracks are mainly generated at eutectic carbides,and the cracks are grown by themselves spreading and joining each other. RE can improve the eutectic carbide′s morphology,inhibit the generation and propagation of thermal fatigue cracks,therefore,promote the activation energy for the crack′s propagation,and especially,which is more noticeable in case of the RE modification in combination with heat treatment.

Effect of heat treatment on microstructure and mechanical properties of Ti-containing low alloy martensitic wear-resistant steel

Effects of quenching temperature and cooling conditions(water cooling and 10%NaCl cooling)on microstructure and mechanical properties of a 0.2%Ti low alloy martensitic wear-resistant steel used for die casting ejector plate were investigated.The results show that lath martensite can be obtained after austenitizing in the range of 860-980℃and then water cooling.With an increase in austenitizing temperature,the precipitate content gradually decreases.The precipitates are mainly composed of TiC and Ti4C2S2,and their total content is between 1.15wt.%and 1.64wt.%.The precipitate phase concentration by water-cooling is higher than that by10%NaCl cooling due to the lower cooling rate of water cooling.As the austeniting temperature increases,the hardness and tensile strength of both water cooled and 10%NaCl cooled steels firstly increase and then decrease.The experimental steel exhibits the best comprehensive mechanical properties after being austenitized at 900℃,cooled by 10%NaCl,and then tempered at 200℃.Its hardness,ultimate tensile strength,and wear rate reach551.4 HBW,1,438.2 MPa,and 0.48×10^(-2)mg·m^(-1),respectively.

A super wear-resistant coating for Mg alloys achieved by plasma electrolytic oxidation and discontinuous deposition

Magnesium alloys are lightweight materials with great potential,and plasma electrolytic oxidation(PEO)is effective surface treatment for necessary improvement of corrosion resistance of magnesium alloys.However,the∼14µm thick and rough PEO protection layer has inferior wear resistance,which limits magnesium alloys as sliding or reciprocating parts,where magnesium alloys have special advantages by their inherent damping and denoising properties and attractive light-weighting.Here a novel super wear-resistant coating for magnesium alloys was achieved,via the discontinuous sealing(DCS)of a 1.3µm thick polytetrafluoroethylene(PTFE)polymer layer with an initial area fraction(A_(f))of 70%on the necessary PEO protection layer by selective spraying,and the wear resistance was exceptionally enhanced by∼5500 times in comparison with the base PEO coating.The initial surface roughness(Sa)under PEO+DCS(1.54µm)was imperfectly 59%higher than that under PEO and conventional continuous sealing(CS).Interestingly,DCS was surprisingly 20 times superior for enhancing wear resistance in contrast to CS.DCS induced nano-cracks that splitted DCS layer into multilayer nano-blocks,and DCS also provided extra space for the movement of nano-blocks,which resulted in rolling friction and nano lubrication.Further,DCS promoted mixed wear of the PTFE polymer layer and the PEO coating,and the PTFE layer(HV:6 Kg·mm^(−2),A_(f):92.2%)and the PEO coating(HV:310 Kg·mm^(−2),A_(f):7.8%)served as the soft matrix and the hard point,respectively.Moreover,the dynamic decrease of Sa by 29%during wear also contributed to the super wear resistance.The strategy of depositing a low-frictional discontinuous layer on a rough and hard layer or matrix also opens a window for achieving super wear-resistant coatings in other materials.

Greatly enhanced corrosion/wear resistances of epoxy coating for Mg alloy through a synergistic effect between functionalized graphene and insulated blocking layer

The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification process,which cannot provide sufficient protection.In the current study,we design a double-layer epoxy composite coating on Mg alloy with enhanced anti-corrosion/wear properties,via the spin-assisted assembly technique.The outer layer is functionalized graphene(FG)in waterborne epoxy resin(WEP)and the inner layer is Ce-based conversion(Ce)film.The FG sheets can be homogeneously dispersed within the epoxy matrix to fill the intrinsic defects and improve the barrier capability.The Ce film connects the outer layer with the substrate,showing the transition effect.The corrosion rate of Ce/WEP/FG composite coating is 2131 times lower than that of bare Mg alloy,and the wear rate is decreased by~90%.The improved corrosion resistance is attributed to the labyrinth effect(hindering the penetration of corrosive medium)and the obstruction of galvanic coupling behavior.The synergistic effect derived from the FG sheet and blocking layer exhibits great potential in realizing the improvement of multi-functional integration,which will open up a new avenue for the development of novel composite protection coatings of Mg alloys.

Enhanced wear resistance,antibacterial performance,and biocompatibility using nanotubes containing nano-Ag and bioceramics in vitro

A good Ti-based joint implant should prevent stress shielding and achieve good bioactivity and anti-infection performance.To meet these requirements,the low-elastic-modulus alloy—Ti–35Nb–2Ta–3Zr—was used as the substrate,and functional coatings that contained bioceramics and Ag ions were prepared for coating on TiO_(2)nanotubes(diameter:(80±20)nm and(150±40)nm)using anodization,deposition,and spin-coating methods.The effects of the bioceramics(nano-β-tricalcium phosphate,microhydroxyapatite(micro-HA),and meso-CaSiO_(3))and Ag nanoparticles(size:(50±20)nm)on the antibacterial activity and the tribocorrosion,corrosion,and early in vitro osteogenic behaviors of the nanotubes were investigated.The tribocorrosion and corrosion results showed that the wear rate and corrosive rate were highly dependent on the features of the nanotube surface.Micro-HA showed great wear resistance with a wear rate of(1.26±0.06)×10^(−3)mm^(3)/(N·m)due to adhesive and abrasivewear.Meso-CaSiO_(3)showed enhanced cell adhesion,proliferation,and alkaline phosphatase activity.The coatings that contained nano-Ag exhibited good antibacterial activity with an antibacterial rate of≥89.5%against Escherichia coli.These findings indicate that hybrid coatings may have the potential to accelerate osteogenesis.

Influence of Heating Temperature on Property of Low Chromium Wear Resistant Cast Iron Containing Rare Earth

The influence of heating temperature on mechanical properties of low chromium wear resistant cast iron containing rare earth elements was studied by means of metallographic examination, scanning electron microscopic examination and mechanical property test. The experimental results show that heating temperature has great effect on impact toughness (α_k), bending fatigue (σ_(bb)) and relative toughness (σ_(bb)×f), but little effect on hardness (HRC). When the specimen was held at 960 ℃ for 3 h, it has better comprehensive mechanical properties, and the reason and regularity of the change for mechanical properties of the cast iron were reviewed.

Study and Application of Heat Treat ment of Multi-Element Wear-Resistant Low-Alloy Steel

The effects of heat treatment on the properties of multi element wear-resistant low-alloy steel （MLAWS） which is used to make the liner of rolling mill torus were researched. The results show that when quenching temperature is lower than 900℃, the hardness increases with the increase of temperature, and when quenching temperature is higher than 900℃, the hardness decreases with the increase of temperature. As quenching temperature is lower than 920℃, the effect of quenching temperature on the impact toughness is not obvious. When quenching temperature is higher than 920℃ , impact toughness decreases with the increase of temperature. When tempering temperature is higher than 450 ℃ , the hardness begins to decrease obviously. After tempering at 350℃, the best wear resistance was obtained. According to the service condition of rolling mill torus liner, the MLAWS is quenched from 900-920 ℃ and tempered at 350-370℃.