In order to improve the abrasion property of polyoxymethylene (POM), diamond like carbon (DLC) film was deposited on POM substrate by the method of magnetic filtered cathodic vacuum arc deposition (MFCVAD). X-ray photoelectron spectroscopy (XPS) showed that the sp(3) fraction decreased with the negative bias voltages increased. According to the result Of the nano-indenter, the hardness of POM plates coated with DLC films was significantly harder than POM substrate. The results of ball-on-disc tribological testing demonstrated that the hardest DLC film had the lowest friction coefficient (0.11). The evaluation of in vitro platelet adhesion test indicates that the numbers of adhered and activated platelet on the DLC film deposited under the condition of 0V and 9min were remarkably decreased compared with that of the untreated POM.

Percutaneous transluminal coronary angioplasty(PTCA) has become increasingly important in the therapy of coronary artery disease. However, the high restenosis occurrence of 20%～30% in patients limits the applications of this method, but the pathogenesis of restenosis has not yet been fully understood.In this paper, static organ culture system was set up to study the process of restenosis formation after PTCA. The common carotid arteries of atherosclerotic rabbits after PTCA were cultured in the artery organ-culture system and maintained in culture for 7 days. After 1d, 2d, 3d, 4d, 5d, 6d and 7d, MTT-test showed that the activity of vessels in the organ culture system unchanged. Pathology and histological technic were applied to check the intimal morphology especially the endothelial denudation and intimal hyperplasia. The concentration of chemical cytokines NO releasing in the process of restenosis were measured .The results showed the method of static organ culture could be successfully applied to keep the activity of culture arteries and study the process of restenosis formation after PTCA. The endothelial denudation and inflammatory cytokines releasing had intimately relationship with the restenosis after PTCA.

Si-N-O films have drawn researcher’s much attention recently due to their potential superiority in blood compatibility of biomaterials. In this paper, Si-N-O films were synthesized on <100> silicon substrates by pulsed reactive unbalanced magnetron sputtering a single crystal silicon target with high purity in a mixture atmosphere of Ar and N2. XPS and FTIR results showed the Si-N-O films synthesized at higher N2 flux could be described to random bonding model (RBM). In RBM, the Si2p existed in the form of a-Si3N4 and SiNνO4-ν (ν=0,1,2,3,4) components. Platelet adhesion behavior on Si-N-O films was assessed by platelet adhesion test and Lactate dehydrogenase (LDH) assay, qualitatively and quantitatively separately. The correlativity of film chemical structure and blood compatibility was investigated. The results of platelet adhesion and activation showed that the RBM film with higher N/O ratio exhibited favorable blood compatibility. It was shown that the Si-N-O film with specific composition and chemical bonding state was superior in blood compatibility compared to low temperature isotropic carbon (LTIC).

The weld metals were prepared respectively with three ESAB company 9Cr-1Mo electrodes.The CCT-diagrams of weld metals were analyzed with thermal dilatometer.The fracture mirographs were observed by SEM.The results show that the elements Cr、Ni、C and Mn improve the stability of austenite and make M_S lower.The toughness of OK2 weld metal is the highest among all the three metals after tempering at about 710℃.The carbides precipitating during PHWT make the toughness of these metals lower.

对于 9Cr- 1Mo耐热钢 ,碳化物的类型和分布是维持材料高温力学性能的关键。对于瑞典ESAB公司的三类 9Cr- 1Mo焊条制成的焊缝金属 ,通过研究发现 ,经过 710℃或 74 0℃× 5h的高温回火处理以后 ,三类材料的力学性能变化发生了较大的差异 ,为此用电子显微镜和光学显微镜对材料的微观组织进行了观察。根据微观观察和成分分析的结果发现 ,高温回火热处理后 ,Cr2 3C6 和Cr7C3型碳化物沿晶界和马氏体板条界面以链状或粒状析出长大 ,材料的力学性能因此发生变化 ,同时还发现 ,铌和钒所产生的耐高温碳化物对保持焊缝组织的高温稳定性有重要影响 ,焊条中适当降低碳含量并不会对焊缝的组织和性能产生负面影响

The microstructure of three 12 pct cr steel weld metals with different nickel and nitrogen contents was studied in as-welded condition and after postweld heat treatment with and without intercooling. Tensile strength and impact toughness of the weld metals were investigated in different postweld heat treatment conditions. In weld metals heat treated without intercooling, austenite decomposed by a eutectoid reaction that resulted in M23C6 aggregates around retained δ-ferrite. Two morphologies of M2N and MN precipitates were found in a low-dislocation α-ferrite. It was concluded that these phases were also transformed from austenite. In weld metals heat treated with intercooling, M23C6 precipitates were smaller and more homogeneously distributed. Different MN precipitates were found in the tempered martensite. The fracture mode of the weld metals at room temperature was mainly transgranular cleavage with some fibrous fracture. Intercooling treatment improved Charpy impact toughness of the 12 pct Cr steel weld metals substantially. It was found that the important microstructural factors affecting the impact toughness of the weld metals which were heat treated without intercooling were the sizes of the α-ferrite grains, nonmetallic inclusions, and M23C6 aggregates. For the weld metals heat treated with intercooling, the factors which affect the toughness of the weld metals were the sizes of martensite packets and nonmetallic inclusions.

The microstructure of weld metals of 2.25Cr-1Mo, 5Cr-0.5Mo, 9Cr-1Mo and 12Cr-1Mo type steels was studied with electron microscopy and atom probe field ion microscopy. Many different types of carbides and nitrides precipitated during welding and post-weld heat treatment (MC, M(2)C, M(3)C, M(7)C(3), M(23)C(6), MN, M(2)N). The eutectoid decomposition of retained austenite gave large aggregates of carbides which were found to be detrimental to the impact toughness of the weld metal.

The microstructure of two types of 12% Cr steel weld metals, one with the composition of a common 12% Cr steel and the other with a higher nitrogen content, was studied using TEM (transmission electron microscopy) and APFIM (atom-probe field-ion microscopy) in post-weld heat-treated condition. The microstructure of the 12% Cr weld metals consisted of tempered martensite, retained δ-ferrite, an irregular low-dislocation α-ferrite and precipitates. Precipitates in the weld metals were dominantly M23C6 on different boundaries. Plate-like and fine cubic MN and M2N were found inside the α-ferrite. APFIM analysis showed that M23C6 was almost a pure carbide and MN was almost a pure nitride. Carbon and nitrogen in the weld metals mainly existed in the precipitates. High nitrogen content did not change the composition of the precipitates, but increased the quantity of nitrides. Therefore, in the high nitrogen weld metal, the content of strong nitride-forming elements in the matrix decreased. These results are important in order to understand the strengthening mechanism of the high Cr steel weld metals, as well as of other high Cr heat-resistant steels.

To elucidate the mechanisms determining the creep resistance of high-speed steels during tool service, overtempering at 600°C has been investigated for two alloys modeling the matrix compositions of AISI M2 and T1. Composition changes and coarsening of the secondary hardening precipitates were studied by transmission electron microscopy and field-ion microscopy with atom probe analysis. Strengthening in the peak-hardened state is due to coherent precipitates of types M2C and MC. During overtempering, M2C coarsens too rapidly to be of importance for the sustained strength of the material. The MC precipitates, on the other hand, are fairly stable. Some coarsening does occur, but the MC population is replenished by a second wave of precipitation which makes use of the roughly 50 pct of carbide-forming elements, carbon, and nitrogen, which remained in solid solution after tempering to the peak-hardened state. This precipitation reaction continues for times of the order of the tool life.

The creep rupture behavior (Type IV failure) for weldments of creep strength enhanced ferritic steel is numerically analyzed, using an integrated microstructure- and micromechanics-based finite element model. To account for the large microstructure gradients across weldments, a two-dimensional digital microstructure is constructed based on the actual observed microstructure of ferritic steel weldment by using the Voronoi-tessellation method. According to the fracture mechanism studies and literature experimental observations, the Type IV failure is identified as an intergranular creep fracture in the fine-grained or intercritical heated affected zone (FGHAZ or ICHAZ). In the present study, the following micromechanics model is employed to determine the micromechanical and microstructural origins for the failure process above, accounting for the underlying physical fracture mechanisms at different length scales, including nucleation of grain boundary cavities, their growth by competition of grain boundary diffusion and grain interior creep, viscous grain boundary sliding, and the emergence of microcracks by coalescence and their evolution to the ultimate failure. The methodology demonstrates the capabilities in modeling the Type IV failure and providing quantitative creep rupture lifetime prediction which shows an excellent agreement with long-term creep experimental data for creep strength enhanced ferritic steels and their weldments. In particular, the drop-off in time to rupture at high temperatures and low stress levels in the creep rupture curves is quantitatively predicted, and the transition of failure mechanisms from creep-controlled to diffusion-controlled creep fracture mechanism is illustrated.

This paper reports some recent results on the precipitation of carbides in a few chromium containing steels at relatively high temperatures. Atom probe microanalysis and transmission electron microscopy were used to characterise the microstructure of high speed steels M2 and Tl after overaging at 600°C and a powder metallurgical 12% chromium steel after heat treatment at 750°C and subsequent creep testing at 600° C.

Plating by bombarding a chemical coating with ions has been developed since the 1970s. The present paper describes the results of SEM observations and Auger electron spectroscopy of a Pd film formed on silicon and glass by 80 keV Ne+ ion bombardment of PdCl2. The mechanism and characteristics of the film formation are also discussed in this paper.