Surface Engineering

Volumes 373-374

doi: 10.4028/

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Authors: Bin Shi Xu
Abstract: Entering into the 21st century, remanufacturing engineering has been developed rapidly in China, Especially from 2005, lots of remanufacturing laws and regulations have been released. Remanufacturing engineering is the industrialization of high technology maintenance to the waste productions, and the advanced period of the maintenance engineering and surface engineering. The basic character of surface engineering is synthesis, intercross, compounding, and optimization. Surface engineering takes the “surface” as core. Nano surface engineering is the integration and creation between the nano materials and traditional surface engineering. To adapt the demand of remanufacturing industrialization, five kinds of automatic and intelligentized technologies, namely automatic nano electro-brush plating technology, automatic high velocity arc spraying technology, semi-automatic micro plasma arc welding technology, automatic laser cladding technology, and intelligentized self-repair technology, have been independently innovated.
Authors: Lin Liu, Bo Qin Gu, Ye Chen
Abstract: Three kinds of coating materials, namely Cr2O3 ceramic, Al2O3-TiO2 ceramic and WC-Co cermet, were screened and sprayed on the surface of valve ball by plasma spraying technology, and two kinds of brush plating materials, namely high speed nickel and nickel tungsten, were also screened and brush plated on the surface of valve seat by electrical brush technology. The microstructure and morphology of the plasma sprayed coatings were analyzed by means of scanning electron microscopy. The tribological properties of the plasma sprayed coatings sliding against the high speed nickel and nickel tungsten layers were investigated on a pin-on-disc friction and wear tester. The microhardness, thermal shock property and bonding strength of the coatings were also tested. The results indicate that the sealing pair composed of the valve ball with the plasma sprayed coating of Al2O3-TiO2 and the valve seat with the brush plating layer of nickel tungsten has the best combination property.
Authors: Ling Zhong Du, Wei Gang Zhang, Deng Jun Zhang, Bao Hou Li
Abstract: In order to improve the surface properties of the machine parts, the NiAl cladding Cr3C2 powder were flame and plasma sprayed. The morphology, microstructure, composition and wear properties of the coatings were examined. The results show that due to the exothermal reaction of the Ni and Al elements, the bonding strength of the coatings are improved, and the main compositions of the coatings are Ni3Al inter-metallic compound and Cr3C2. The flame sprayed and plasma sprayed coatings show almost the same micro-hardness and friction coefficient. But the microstructure of the plasma sprayed coating is more compact than that of the frame sprayed one and the wear resistance of the flame and sprayed coatings is 30% and 120% higher than that of the 1045 steel, respectively. The main wear mechanisms of the coatings are plastic deformation and spallation, and the high bonding strength and the uniformly distributed Cr3C2 particles play important anti-wear roles.
Authors: Yong Xiong Chen, Bin Shi Xu, Xiu Bing Liang, Yi Xu
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”.
Authors: Z.W. Huang, Zhong Guang Wang, Shi Jie Zhu, F.H. Yuan, F.G. Wang
Abstract: A cast nickel based superalloy M963 was coated by high-velocity oxy-fuel (HVOF) spraying process. The effect of HVOF MCrAlY coating on thermo-mechanical fatigue (TMF) and isothermal fatigue (IF) in M963 was studied to understand fatigue life and failure mechanisms in coated and uncoated M963 alloy. Two types of TMF tests, i.e. in-phase (IP) and out-of-phase (OP), were performed in temperature range of 450~900°C, and IF tests were conducted at 900°C. It was found that the coating had a detrimental effect on fatigue life under OP TMF, while a beneficial effect of the coating existed under IP TMF and IF. Crack initiation time in the coated specimen was shorter than that in the uncoated specimen and the former’s crack density was higher than the latter’s one under OP TMF. The relationship of deformation and fracture response with fatigue life was discussed based on microscopic analysis.
Authors: Z.X. Ding, Q. Wang, Zheng Lin Liu
Abstract: In the paper, nanostructured, multimodal and conventional WC-12Co cermet coatings were sprayed by HVOF and the properties and structures of the coatings such as microhardness, microstructure, phase composition were compared. Finally sand solid and slurry erosion wear tests were carried out and their wear failure mechanisms were explored by XRD and SEM analysis. Research results show that microstructures of nanostructured and multimodal WC-12Co coatings prepared by HVOF are dense with little porosity, and their microhardness values are obviously higher than conventional WC-12Co coating. As well, it was found that nanostructured and multimodal WC-12Co coatings exhibited better sand solid and slurry erosion wear resistance in comparison with conventional coating and nanostructured WC-12Co coatings possessed the best sand solid erosion resistance properties at large impact angles and slurry erosion wear resistance. Testing results also show that although decarburization of WC occurred during spraying multimodal and nanostructured WC-12Co powders, the decarburization of WC for the nanostructured powder was more severe.
Authors: Shu Xiang Song, Wei Zhi Yao, Zhang Jian Zhou, Wei Wei Cong, Yao Ma, Chang Chun Ge
Abstract: Tungsten has been decided as the plasma facing material (PFM) for some high heat flux regions of the divertor in the International Thermo-Nuclear Experimental Reactors (ITER). In this paper, our efforts concentrated on the functionally gradient W/Cu coating fabricated on the oxygen free copper by atmosphere plasma spraying under the inert gases protection. The functionally gradient W/Cu coatings were designed to relieve the thermal stress during the spraying processes. For comparison, the tungsten coatings were also deposited directly onto the copper substrates by the same technology. XRD, SEM and EDS were applied to identify the phases, morphologies and compositions of these coatings. Tensile tests were performed to measure the bonding strength between the coatings and the substrates. Furthermore, water quenching and high heat loading experiments using a pulse laser beam were also carried out to estimate the thermal shock properties of these coatings.
Authors: Hua Ling Deng, Guang Long Li, Yun Jing Song, Shi Rong Xiao
Abstract: The CrB Particles Reinforced MMC Coating was prepared by using high velocity arc spraying (HVAS) method. Through a series of experiments, including metallographic, SEM and EPMA investigation, the microstructure and composition of the coating were analyzed in details. Additionally, the abrasion resistance mechanism of the coating was studied through field test and observation on the abrasion surface of the coating under the SEM. The results show that the microstructure of the coating is characterized by typical compact laminated structure composed of successive metal matrix and hard particles mainly of borides of chromium and oxides of chromium. The abrasion resistance mechanism of the coating lies in two aspects. One is that the hard particles scatter evenly and dispersedly in the coating, which can reinforce the coating and play a barrier role to hinder the movement of the abrasion particles. The other is that the metal matrix with well ductility and toughness make a buffer action to the impact caused by the abrasion particles, thereby the waste rate of the coating can be greatly slowed down. The results also show that the hardness, shape and quantity of the reinforced particles have magnificent influence on the abrasion resistance of the coating made in this paper.

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