Effect of heat treatment on the microstructure and hardness of C-Cr-W-Mo-V-RE Fe-based hardfacing layer

0IntroductionHot-rollers and scissors are the critical parts of thesteel rolling equipments.At present,the surface soften-ing,the early wearing and the tearing are the primary rea-sons for the lowservice life of the hot-rollers and scissors.Although hardfacing has been applied to repaire the partseasily being worn and torn,such as the hot-rollers and thescissors,and has been obtained economic benefits[1-3],this technology has common problem:if the hardfacing lay-er contains more excessive allo…     

高温精炼处理对铸造镍基高温合金组织与性能的影响

研究了高温精炼处理对铸造镍基高温合金组织与性能的影响.普通铸造镍基合金枝晶组织粗大,晶界碳化物呈链状分布,晶内碳化物呈草体汉字状密集分布于枝晶间,是合金塑性低的主要原因.经高温精炼处理后,合金的枝晶组织细化,晶界及枝晶间的碳化物数量减少,γ γ共晶相数量增加,晶界碳化物呈不连续质点状分布,晶内碳化物的密集程度下降,拉伸塑性和蠕变(持久)寿命得以明显提高.经1 650℃,5 min高温熔体处理后,合金室温延伸率由3.5%提高到9.2%,700℃高温塑性由2.0%提高到8.0%,900℃高温塑性由2.8%提高到9.6%,蠕变寿命由34 h提高到52 h,蠕变塑性由4.3%提高到6.11%.推荐的最佳高温精炼处理制度为1 650℃保温4 h.分析了高温精炼处理对合金液态结构、凝固组织与性能的影响机理.     

Formation of the Fe(II)-Fe(III) hydroxysulphate green rust during marine corrosion of steel

Rust layers formed on steel sheet piles immersed 1 m above the mud line for 25 years were analysed by Raman spectroscopy, scanning electron microscopy and elemental X-ray mappings (Fe, S, O). They consist of three main strata, the inner one mainly composed of magnetite, the intermediate one of iron(III) oxyhydroxides and the outer one of hydroxysulphate green rust GR(SO₄²⁻). Simulations of GRs formation in solutions having large [Cl⁻]/[SO₄²⁻] ratios revealed that the hydroxysulphate GR(SO₄²⁻) was obtained instead of the hydroxychloride GR(Cl⁻), as demonstrated by X-ray diffraction and transmission Mössbauer spectroscopy analyses. Measurements of the [S], [Fe] and [Cl] concentrations allowed us to establish that GR(SO₄²⁻) formed along with a drastic impoverishment of the solution in sulphate ions; the [Cl⁻]/[SO₄²⁻] ratio increased from 12 to 240. The GR, acting like a “sulphate pump”, may favour the colonisation of the rust layers by sulphate reducing bacteria.     

Thermal stability behaviors of Cr(N,O)/CrN double-layered coatings by TGA/DTA analysis

In this study, Cr(N,O)/CrN double-layered coatings were synthesized using the cathodic arc deposition (CAD) process. CrN film was first deposited onto a substrate as an interlayer to ensure better adhesion, and Cr(N,O) film was subsequently deposited on top of the CrN layer as the surface layer. Variation in the Cr(N,O) coating composition was achieved through changing the O₂/N₂ flow ratio during the last stage of processing. Phase structure, chemical composition, and morphology of the resulting coatings were analyzed and observed using the X-ray diffractometer, Auger electron spectrometer and SEM. In addition, oxidation behavior of the coatings was investigated using TGA/DTA methods. The tests were carried out by increasing temperature up to 1000 °C in ambient air. With the introduction of oxygen gas during the CAD process, a superficial layer was produced in the Cr(N,O) constituent containing CrN and Cr₂O₃ phases. The formation of the oxide phase attributed to the reaction of chromium and oxygen was more favorable than that of chromium and nitrogen. The results also showed that Cr(N,O)/CrN double-layered coatings exhibited superior oxidation resistance at elevated temperature than that of CrN single-layer coated specimen (870 °C vs. 750 °C).     

Influence of heat treatment on tribological behaviors of novel wrought aluminum bronze

1　ＩＮＴＲＯＤＵＣＴＩＯＮＡｌｕｍｉｎｕｍｂｒｏｎｚｅｐｏｓｓｅｓｓｅｓｅｘｃｅｌｌｅｎｔｐｈｙｓｉｃａｌ,ｍｅｃｈａｎｉｃａｌａｎｄｔｒｉｂｏｌｏｇｉｃａｌｐｒｏｐｅｒｔｉｅｓ .Ｉｔｉｓａｖａｉｌａｂｌｅｆｏｒｍａｋｉｎｇｗｅａｒ ｒｅｓｉｓｔｉｎｇａｎ     

深冷处理与工模具的耐磨性

热处理后的金属材料再经低落曙处理，其力学能明显提高，尤其是高碳高合金工模具钢的耐磨性提高特别显著。本文着重研究了应用面较广的Ｗ６Ｍｏ５Ｃｒ４Ｖ２钢的处理工艺制度，组织性能及其磨损机理。     

矢功率谱与RBF网络结合在旋转机械故障诊断中的应用

与传统功率谱相比,矢功率谱融合了多通道的能量信息,反映的信息更全面.径向基函数网络具有良好的推广能力和分类能力.基于此,本文结合矢功率谱和径向基函数网络,提出了一种新的故障识别方法,该方法以矢功率谱为特征向量,径向基函数网络为分类器.并以转子裂纹、转子不对中、油膜涡动为例进行实验研究,实验结果表明,该方法是有效的.     

基于弹塑性有限单元法的齿轮轴数值模拟

基于弹塑性有限单元法的一般原理,建立了齿轮轴热处理的热力耦合分析模型,对12Cr齿轮轴热处理工艺中温度、应力以及相变的分布情况进行了模拟,研究了加热规范的成形性,并与实际结果比较证实本模型的有效性,为有限单元法在热处理工艺模拟中的应用奠定了一定基础。     

基于消失模铸造的AZ91镁合金组织改性研究

研究了机械振动处理技术对AZ91合金在消失模铸造条件下的组织形貌的影响,以及该铸态组织在半固态等温热处理过程中的组织演变,并探讨了振动细化机理和组织演变机理。结果表明:机械振动能显著地细化AZ91合金的铸态组织;在液固相区570℃等温处理时,其铸态组织都能由枝晶转变为球状晶组织,而且振动处理可获得更加细小并且均匀的球状组织。等温处理时间过长时,两种组织都会发生合并长大。     

Mn,Zr对Mg-Gd-Y合金组织与力学性能的影响

研究了微量Mn、Zr对Mg-13%Gd和Mg-9%Gd-4%Y合金铸态和挤压后的微观组织及力学性能的影响.结果表明:在铸态,含Zr合金的晶粒明显小于不含Zr的合金,而Mn对合金的铸态显微组织影响不大;将Mg-9%Gd-4%Y-0.6%Mn和Mg-9%Gd-4%Y-0.6%Zr合金挤压后,都可以得到非常细小均匀的等轴晶,晶粒尺寸约14 μm;这两个合金在挤压时效态(T5)的力学性能都明显优于WE54合金的,且Mg-9%Gd-4%Y-0.6%Zr合金比Mg-9%Gd-4%Y-0.6%Mn合金性能更好.