Papers by Author: Xiu Bing Liang

Abstract: An automatic high velocity arc spraying process was used to deposit a type of FeCrBSiMoNbW amorphous/nanocrystalline coating with substrate of AZ91 magnesium alloy. The microstructure of the coating was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDAX). The coating is about 250μm in thickness with low porosity and oxids. The results show that the microstructure of the coating can be classified into two regions, namely, a full amorphous phase region and homogeneous dispersion of α-Fe (Cr) nanocrystals with 30-80 nm in a residual amorphous region. Mechanical properties, such as nano-hardness, elastic modulus, were analyzed. The experimental results show that the coating has high nano-hardness and elastic modulus. The friction and wear experiments were operated on UMT-2 micro friction tester. The relative wear resistance of the FeCrBSiMoNbW coating is about 2 times higher than that of the conventional 3Cr13 coating under the same conditions. The main wear mechanism of the amorphous/nanocrystalline coating is the typical brittle spalling.

Abstract: High velocity arc spraying (HVAS) process was used to deposit Al-Ni-Y-Co and Al-Ni-Mm-Fe amorphous/nanocrystalline composite coatings onto AZ91 Mg alloy substrate. Their microstructure was characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The coatings are both about 500 μm in thickness with fully dense and low porosity. The microstructure of the coatings is classified into two regions, namely, a full amorphous phase region and homogeneous dispersion of fcc-Al and some intermetallic nanoscale particles in a residual amorphous matrix region. Vickers micro hardness of the coatings was also measured. The average Vickers micro hardness of Al-Ni-Y-Co and Al-Ni-Mm-Fe coating is about 311 HV and 340 HV, respectively.

Abstract: Two kinds of high-entropy alloy coatings of FeCrNiCoCu and FeCrNiCoCuB were deposited on AZ91 magnesium alloy substrate using high velocity arc spraying technology. Microstructure and general mechanical properties of the coatings were investigated with Scanning Electronic Microscope (SEM), X-Ray Diffraction instrument (XRD), microhardness tester and strength bond tester. The results show that the two kinds of coatings exhibit compact layered microstructure and the phase lattice type are both FCC, the microhardness of the FeCrNiCoCu and FeCrNiCoCuB coatings are 414HV0.1 and 342HV0.1 respectively, the bond strength are 36.9 MPa and 33.6 MPa respectively.

Abstract: The most severe corrosion of offshore steel structure occurs in splash zone. There are many factors affecting the steel structure corrosion in the splash zone, such as corrosion problems caused by seawater and effect of impacted brought by the ocean wave. Considering the corrosion characteristics in splash zone and the corrosion invalidity behaviors of offshore steel structure, the Zn-15Al, Al-RE, Zn-Al-Mg-RE and FeBSiNb uncrystal coatings were prepared by automatic high velocity arc spraying. The different anti-corrosion behaviors of the four coatings were studied through the corrosion comparative tests and the microstructures analyzed of the coatings before and after the corrosion tests. The anti-corrosion coating systems suitable for using on surface of steel structure corrosion in the splash zone were found, which provided technique guarantee for extending the using life of offshore steel structures.

Abstract: High performance cemented carbide YG610 was adopted for remanufacture hardness deposited materials cutting experiment. The experiment results showed that the same conclusions can be drawn from two group orthogonal experiments. The influence order on cutting capability of cutting tools was: feed rate﹥cutting speed﹥ cutting depth. The cutting length of cutting tools increases monotonously with the feed rate decrease. And the effects by the cutting depth were comparatively small, which is almost negligible in hardness materials cutting. Therefore，low feed rate and large depth of cut are beneficial to keep cutting capability of cutting tools and improve manufacturing productivity. By the results of two orthogonal experiments and extreme deviation analysis, the optimal scheme for cutting parameters were achieved after calculating the best level of the factor.

Abstract: Structure as well as magnetic and magnetoelastic properties of nanocrystalline (Fe,Co)-(Hf,Zr)-Cu-B alloys (HITPERM-type) were investigated in order to find out which factors are responsible for the magnetic hardening of these magnetically soft materials. Magnetoelastic anisotropy, caused by the presence of cobalt, was found to play the predominant role in the observed increase of coercive field. On this basis, guidelines on chemical composition and crystallisation process selection were suggested for two fields of application: soft magnetic cores and sensors or actuators cores.

Abstract: A new automatic high velocity arc spraying system was developed. The system was consisted of five units, i.e. central control unit, operating machine, positioner, touching screen and high velocity arc spraying equipment. The central control unit is controlled by a program, controlling other four units. Spraying parameters could be input and modified on the touching screen during spraying. The moving of spraying gun was carried out by motion arm of the operating machine. The rotational velocity and angle of components to be sprayed was controlled by positioner. The spraying process for a cylinder body of automobile engine with the system was introduced in detail. The auto and manual arc spraying have been used to fabricate coating. The microstructure of the coatings prepared by the two spraying processing was analyzed. The result shows that the auto sprayed coating has a more uniform and compact structure than that of the manual sprayed coating.

Abstract: Cored wires and high velocity arc spraying (HVAS) technologies have been applied to produce Zn-Al-Mg-RE coating on A3 steels. The durability of coating in terms of corrosion resistance is the focus of this paper. The detailed degradation mechanism has been investigated using electrochemical-monitoring techniques supported by precise pre-test and post-test microscopical examination using Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). Zn-Al-Mg-RE coating shows a typical aspect of layered heterogeneous structure, the existing of ZnAl2O4 and MgAl2O4 implies the good anti-corrosion feature. The polarization curves showed that Zn-Al-Mg-RE coating exhibits passive behavior at 0.5h and 16h immersion, but at 600h, it begins to dissolute. In contrast, the anti-corrosion performance isn’t cut down. The corrosion potential moves to the noble direction step by step, along with the current density drops gradually. After corrosion, it has been observed that the coating surface is jointed by flaky lamellar products and dense without obvious defects and pores. It is postulated that with the addition of RE, the porosity of the coating is reduced, meanwhile, the stability of the products layer can reinforce the self-sealing effect of the coating distinctively.

Abstract: A new type of composite coating (321—Al coating) was prepared by using the 321 austenitic stainless steel wire feed stock as the anode and aluminum wire as the cathode in arc spraying process. In order to compare with the new composite coating, the traditional 321 coating with twin 321 stainless steel wires was fabricated. The microstructure and wear resistance of the coatings were characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersion spectroscope (EDS) and MM-200 ring-block type sliding wear tester. Results showed that, except for the aluminum phase addition in the 321—Al coating, no other extra phases produce in comparing with the 321 coating. However, due to the additional aluminum, the 321—Al coating performs quite different microstructure characteristics and tribological behavior. The oxygen content and microhardness of the 321—Al coating are lower than that of the 321 coating, but wear losses are pretty much under the oil lubricated sliding condition. The effect of the microstructure on the wear behavior of the 321—Al coating was also discussed, which is mainly relevant to the characteristic of “ductile aluminum and hard stainless steel composite phases inter-depositing”.