减小碳钢轴承套圈渗碳淬火变形研究

云南楚雄轴承厂采用４５＃钢制作轴承套圈，经反射炉固体渗碳无规则直接淬火，引起套圈椭圆变形较为严重，淬火后长径之差大大超过技术指标要求，为此，造成产品报废率达３０％以上，本试验目的，在现有设备上，通过改变淬火方式和淬火介质达到减小套圈椭园度变形废品由原来的３０％以上降低到１０％以上。     

金属钨粉碳化机理

本文研究了金属W粉的碳化机理。结果表明,电解显示技术能清晰显示不完全碳化的W颗粒中的复相组织;WC晶粒度的分散性与原始W颗粒度的均匀性有关,对于粗W粉,其颗粒完整性对WC的晶粒度有影响;在通常的碳化温度下,为制取晶粒度均匀的粗晶WC不宜使用异常租大的W粉;W粉碳化过程中颗粒表层多晶WC向W核心的扩展是通过内层的W_2C与扩散到内部的碳原子反应的结果。     

Thermodynamic Analyses on Oxygen and Carbon Potentials of Impure Helium

Equilibrium oxygen and carbon potentials of impure He containing small amounts of impurities such as CO, CO₂, CH₄, H₂, H₂O and O₂ at 1,073 and 1,273 K were studied. The calculation of equilibrium composition of impurities was carried out assuming the gas-gas and gas-metal reactions. The diagrams, expressed with atomic oxygen fraction ō/S and atomic carbon fraction [Cbar]/S were represented and showed a wide range of equilibrium oxygen and carbon potentials of impure He. A parameter, (ō-[Cbar])/S showing the difference between atomic oxygen and carbon fraction, was found to give a measure of both oxygen and carbon potentials of gas mixtures. The results of the calculation showed that the oxygen and carbon potentials of the impure He with (ō-[Cbar])/S value of around zero was easily affected by the small variation of the gas composition. The corrosion behaviors of Inconel 617 in various impure He gases at 1,273 K could be explained by (ō-[Cbar])/S values.     

提高成型辊使用寿命的研究和实践

通过对 GCr15钢制 10 1.6× 3.5mm焊管成型辊的失效分析 ,确认其失效形式为麻点剥落。根据其尺寸较大这一突出特点 ,结合其受力状态以及价格因素等 ,改用 4 5钢经渗碳、喷液淬火 ,提高了其工作面的硬度和强度 ,克服了麻点剥落 ,提高了使用寿命。     

Metal dusting resistance of high chromium alloys

Samples of 5 high Cr‐alloys were discontinuously exposed for 10,000 hours under severe metal dusting conditions, i. e. in flowing 49%CO‐49%H₂‐2%H₂O at 650°C. After each of the 11 exposure periods the mass change was determined and any coke removed and weighed. Metallographic cross sections were prepared after about 4,000 h and 10,000 h. The high Cr‐alloys: 1. PM 2000 (Fe‐19%Cr‐5.5%Al‐0.5%Ti‐0.5%Y₂O₃), 2. Cr‐44%Fe‐5%Al‐0.4%Ti‐0.5%Y₂O₃, 3. Cr‐50%Ni, 4. Cr‐5%Fe‐1%Y₂O₃ and 5. porous chromium showed no or only minute metal dusting attack. Compared to the attack on reference samples of Alloy 601 (Ni‐23%Cr‐14%Fe‐1.4%Al), the metal dusting symptoms were negligible on the 5 high Cr‐alloys, minor coking and pitting and no internal carburization was observed. Because of the high Cr‐content, carbon solution and ingress should be minute, and in addition are inhibited by the formation of a chromia scale, as confirmed for four of the Cr‐rich alloys, and formation of an alumina scale on PM 2000. These alloys could be used for parts exposed to severe metal dusting conditions, and in fact, 50Cr‐50Ni has been applied successfully under such conditions.     

Hot erosion wear and carburization in petrochemical furnaces

High temperature alloy stainless steels used in olefins manufacturing furnaces are exposed to extreme environmental degradation processes inclusive of carburization, oxidation and hot erosion wear. A study was undertaken to understand the hot erosion wear phenomenon in relation to substrate composition, atmosphere, temperature, time and the influence of carburization. An erosion wear test rig was designed and constructed to simulate the wear degradation process up to 1200°C. Results have shown a surprising relationship between erosion wear rate and temperature for the most prominent stainless steel alloy used in the industry. A novel coating technology was developed for mitigation that enables the non‐line‐of‐sight application of protective macro‐coatings typically 1 to 5 mm in thickness. Stainless steel coupons treated with these macro‐coatings have exhibited an enhanced resistance to both oxidation and carburization. These macro‐coatings also provide superior hot erosion wear resistance as compared to the uncoated stainless steel. A thorough examination of the microstructure and micro‐mechanical properties of the coatings is presented. Targeted applications include petrochemical furnace fittings (return bends), thermo‐wells and transfer‐line‐exchanger (TLE) surfaces. Commercial furnace trials of the prototype products have been initiated with some prototypes in field trials for over 18 months. Results of both laboratory accelerated testing and field evaluation will be discussed.     

Study of the metal dusting behaviour of high‐temperature alloys

The corrosion phenomenon named metal dusting has been observed in many high‐temperature industrial plants. An experimental research programme is being carried out into the degradation resistance of wrought and cast commercial and development high‐temperature alloys in H₂/CO gas mixtures at temperatures of 550°C to 750°C. Emphasis is placed on very high carbon activities, consistent with the next generation of steam‐reforming and similar plants that are susceptible to metal dusting. The overall programme is concerned with the mechanisms of initiation and propagation of dusting and the sensitivity to damage of the more resistant alloys, as a function of environmental parameters. Initial tests have been carried out on a number of commercial alloys: Alloy 600, 693, 602CA, 601, 603 XL, 671, 617, 690 (wrought), and H46M (cast). The specimens were exposed to a gas mixture of high carbon activity at 650°C for a total of 1000 hours. Many of the alloys showed at least the initial stages of metal dusting. Preliminary analysis using electron microscopy revealed that initiation of metal dusting is influenced by microstructure, stress state and composition. In some cases, attack was enhanced at stress points, such as corners and edges. Sample holders were found to influence strongly the length of the initiation period for the onset of the corrosion phenomenon. The reaction layers in the alloy beneath areas of damage were analysed by EDX and EPMA. Mechanical characterisation of such areas has been carried out using nanoindentation methods. These early results are discussed in terms of the effectiveness of oxide scales in inhibiting the onset of damage and presence of impurities in the ceramic holder in initiating the onset of damage.     

Oxidation resistance of TiAl alloy treated by plasma Nb-C alloying

In this paper, the duplex treatment of plasma surface niobizing and carburization (Nb-C alloyed or duplex treated) has been performed on TiAl substrates. Cyclic-oxidation tests for untreated and duplex treated TiAl were carried out in static air at 900 °C for 103 h. The mass gain due to oxidation was measured using an electrobalance. The chemical compositions of the Nb-C alloyed layer as well as its microstructure were examined by glow discharge spectrum (GDS) and the optical microscopy (OM). The electronic diffraction spectrum (EDS) and scanning electronic microscopy (SEM) were used to analyze and observe the oxide layers. The phase structures of the oxide scale were identified by X-ray diffraction (XRD). The results show that the oxidation rate of the duplex treated TiAl specimens decreased significantly, compared with the untreated TiAl. The roles of duplex treatment for improving the oxidation resistance are discussed.