Studies on the hot corrosion of a nickel-base superalloy,Udimet 700

The hot corrosion of a nickel-base superalloy, Udimet 700, has been studied in the temperature range 900–950°C. The effect of the amount of Na ₂SO₄ on the corrosion kinetics was determined. Large weight gains and severe corrosion were associated with two different modes of degradation: (1) formation of large, interconnected sulfides beneath the external scale, and (2) formation of a Na₂MoO₄-MoO₃ melt. The corrosion due to formation of the Na₂MoO₄-MoO₃ melt occurred for all the salt-coating thicknesses, whereas, large sulfides were formed only for the heavier coatings of Na₂SO₄. The formation of Na₂MoO₄-MoO₃ melt required an induction period, and the length of the induction period was observed to be a function of the amount of Na₂SO₄ and of temperature.Work funded under NASA Grant NCC 3-43.     

铜合金表面Ni基铸渗层的热疲劳行为研究

研究了铜基表面镍基渗层的热疲劳性能。结果表明:热循环次数小于20次时,渗层表面主要产生氧化,无裂纹产生;当热循环次数超过50次时,渗层与基体的结合界面处以及渗层的表面会产生微裂纹,渗层越厚,渗层与基体的结合界面处出现微裂纹的时间越早;多次热循环后在渗层与基体的结合处出现蚀坑,渗层的损伤形式主要为应力腐蚀。     

GH4169线性摩擦焊接头的焊合率与弯曲强度

论述了高温合金GH4169线性摩擦焊的试验过程。分析了弯曲强度、断裂挠度与焊合率之间的关系及接头的金相组织。结果表明,GH4169线性摩擦焊接头的弯曲强度与焊合率成正比线性关系,断口为韧性断口;断裂强度受摩擦时间的影响较大。     

The Influence of High Temperature Exposure on the Wear Performance of a Ni Based Alloy PTA Coating

Degradation phenomena like wear and corrosion, may have their effects accelerated as components operate at high temperature. The aim of this work is to make an indirect evaluation of the influence of high temperature exposure on wear behavior of Ni coatings. A Ni-Cr-Mo-W alloy, was deposited with Plasma Transferred Arc (PTA) process. An indirect approach based on the Ahrrenius relationship was used to evaluated long time exposures at high temperatures. To simulate longer exposures at lower temperatures, coatings were exposed to higher temperatures for the same time interval. So coatings were soaked in an air furnace at 650℃, 1000℃ and 1200℃. Metal/metal wear behavior was evaluated by pin-on-disc tests. Pins were removed from the coatings by eletrodischarge machining and rubbed against a VC31 quenched and tempered tool steel. Two sets of wear tests were run at 2m/s, for different loads (0.5, 1.0, 2.0 and 3.0Kg) and for different sliding distances (120, 720, 1080, 1440 and 1800m).Coatings characterization was done by scanning electronic microscopy and Vickers microhardness. Results showed as temperature is increased, coatings wear performance is altered,and this is associated with microstructural changes.     

稀土元素Y对K38G高温合金800 ℃恒温氧化行为的影响

对加入0.05mass%～0.5mass%稀土Y铸造的K38G高温合金800 ℃恒温的氧化行为进行了研究.结果表明,含Y铸态K38G合金的氧化动力学曲线偏离了抛物线规律，接近于立方规律；Y有效抑制了该合金的内氧化；当Y含量达0.5mass%时，该合金中析出富Y相，降低了其氧化抗力.       

初生M6C的形成及其对高钨铸造模具高温合金的影响

高钨铸造合金已用于铸造大型模具，由于大量初生M6C碳化物的形成使模具变脆，需探明初生M6C的形成条件．实验表明当含碳量超过0．15％时，合金中易析出初生M6C，而10％Co起有效的抑制作用．初生M6C是在1375℃时形成的，它对通过固-液范围的冷却速度十分敏感，快冷抑制它的形成．铸件中M6C的形成存在明显的尺寸效应，枝晶间距大于150μm时的较厚截面极易形成毫米量级的M6C，严重的损伤合金的高温强度．因此对大截面的模具合金，为防止初生M6C的析出，合金中最好保持0．04％—0．07％C和10％—15％Co．     

喷焊工艺对钛基体镍基涂层显微组织和性能的影响

采用常规喷焊工艺和改进喷焊工艺,在Ti-6Al-4V合金表面上制备了镍基耐磨涂层,分析了涂层的形貌和合金元素的扩散,测试了涂层的显微硬度,定性地研究了基体和涂层的结合性能.结果表明:改进工艺所制备的涂层组织和性能均优于常规工艺的,涂层组织的均匀性大大提高,晶粒得到细化;基体和涂层为明显的冶金结合;涂层显微硬度的变化沿层深方向呈连续性和渐变性,其表层显微硬度高达HV933.2.采用合理的喷焊工艺能够在钛合金表面制备出性能优良的耐磨涂层.     

IC-6高温合金及其防护性涂层的摩擦特性

采用电弧离子镀技术在IC－高温合金上沉积NiCrAlY涂层。研究了NiCrAlY涂层及IC－6高温合金在室温和600℃空气中无润滑状态下，以K17高温合金为摩擦副的摩擦特性。采用带有能谱的扫描电镜（SEM／EDX）分析IC－6高温合金和NiCrAlY涂层磨损表面的形貌和成分。实验结果表明，室温条件下摩擦时，一些碎屑从K17合金上脱落下来，在IC－6合金及NiCrAlY涂层表面上形成磨粒，随着摩擦时间延长，磨损表面元素发生氧化。试样在环境温度在600℃摩擦时，NiCrAlY涂层的表面比较快的形成氧化膜，减少金属－金属间的直接接触。环境温度升高后，摩擦表面温度也随之升高，氧化物的粘滞性增强，600℃时，合金和涂层摩擦系数都有不同程度的减小。     

镍基高温合金真空感应熔炼脱氮的研究

研究了采用CaO坩埚真空感应熔炼镍基高温合金过程中的脱氮行为.试验表明在精炼过程中加Al对脱氮有促进作用;加Ti则对脱氮有明显不利影响;提高熔炼时的真空度是促进脱氮的有力措施.