硫酸镍溶液中脱除铝的试验研究

研究了采用中和沉淀法脱除粗质NiSO_(4)溶液中的杂质Al^(3+)的方法。用Ca O作中和除Al^(3+)剂,考察了CaO用量,反应终点p H值,反应温度,搅拌转速等因素对粗质Ni SO_(4)溶液中Al^(3+)脱出率的影响。试验结果表明:在Ca O加入量为Al^(3)+摩尔理论总量的5倍,终点p H值5.0~5.5,反应时间为1 h,温度为(80~90)℃,搅拌转速为300 r/min,达到终点p H值并稳定0.5 h条件下,Al3+脱除率大于99%;Ni^(3+)损失率小于1.5%。

Fretting wear and friction oxidation behavior of 0Cr20Ni32AlTi alloy at high temperature

The fretting wear behavior of 0Cr20Ni32AlTi alloy was investigated with crossed cylinder contact under 80 N at 300 and 400 °C.Wear scar and debris were analyzed systematically by scanning electron microscopy and X-ray photoelectron spectroscopy.The results show that the friction logs are mixed fretting regime and gross slip regime with the magnitudes of displacement of 10 and 20 μm,respectively.Severe wear and friction oxidation occur on the material surface.A large number of granular debris produced in the fretting process can be easily congregated and adhered at the contact zone after repeated crushes.The resultant of friction oxidation is mainly composed of Fe3O4,Fe2O3,Cr2O3 and NiO.Temperature and friction are the major factors affecting the oxidation reaction rate.The fretting friction effect can enhance the oxidation reaction activity of surface atoms of 0Cr20Ni32AlTi alloy and reduce the oxidation activation energy.As result,the oxidation reaction rate is accelerated.

Microstructure and abrasion wear behavior of Ni-based laser cladding alloy layer at high temperature

Ni-based alloy coating on 21-4-N heat-resistant steel was prepared using CO2 laser, and the high-temperature abrasion wear was tested. The microstructure of this cladding layer and its abrasion wear behavior at high temperature by changing compositions and temperatures were investigated by means of optical microscope and scanning electron microscope. Among the three compositions of cladding layer, i.e. Ni21+20%WC+0.5%CeO2, Ni25+20%WC+0.5%CeO2 and Ni60+20%WC+0.5%CeO2, the experimental results show that Ni21+20%WC+ 0.5%CeO2 cladding layer is made up of finer grains, and presents the best abrasion wear behavior at high temperature. The wear pattern of laser cladding layer is mainly grain abrasion at lower temperature, and it would be changed to adhesive abrasion and oxide abrasion at higher temperature.

Influence of niobium and molybdenum addition on microstructure and wear behavior of laser-borided layers produced on Nimonic 80A-alloy

Laser alloying was used for production of thick layers on surface of Nimonic 80A-alloy.For laser surface modification,three types of pre-coated pastes were applied:with amorphous boron,with amorphous boron and molybdenum as well as with amorphous boron and niobium.The microstructure,hardness and wear resistance of produced layers were studied in details.The presence of different types of borides in re-melted zone depended on the paste composition and caused an increase in hardness up to about HV 1000.The wear resistance was evaluated by calculation of mass wear intensity factor Imw and relative mass loss of specimen and counter-specimen.The wear behavior of the tested frictional pairs was determined by 3D interference microscopy,scanning electron microscopy equipped with EDS microanalyzer.The significant increase in abrasive wear resistance was observed in comparison to untreated Nimonic 80A-alloy.The lowest mass loss intensity factor was characteristic of laser-alloyed Nimonic 80A-alloy with boron and niobium(Imw=1.234 mg/(cm2?h)).Laser alloyed-layers indicated abrasive wear mechanism with clearly visible grooves.Laser alloying with boron and niobium resulted in the additional oxidative wear mechanism.In this case,EDS patterns revealed presence of oxygen on the worn surface of specimen.

An Experimental Study on Slotting of Inconel 718 Thin Sheet

Many difficult-to-cut materials such as Ni-base super alloy, titanium alloy, and austenite stainless steel which are used extensively in aerospace generally have high strength-to-weight ratios, high corrosion resistance, high strength retention ability at elevated temperatures, and low thermal conductivity. These characteristics can result in uneven tool wear and chatter vibration. Therefore, determining the appropriate end-milling conditions is more difficult for difficult-to-cut materials than for other materials. There has been much research on the high-speed milling of difficult-to-cut materials, and effective end-milling conditions, end-mill tool shapes, and processing methods have been reported. In addition, irregular pitch and lead end-mills with different helix angles have been developed by tool maker＇s to reduce chatter vibration, making it easier to perform high-speed milling. However, there have been few reports of slotting information useful for determining appropriate end-milling conditions and processing methods for Ni-base super alloy. The aim of this study is to derive end-milling condition with high efficiency grooving process for Ni-base super alloy （Inconel 718） sheet. Effects of cutting parameters were examined from the view point of cutting resistance, ＂tool tip maximum temperature and tool flank wear width. As a result from experiments, if the grooving process condition of axial depth of cut is smaller than other conditions on the same material removable rate value, it has been found that it is possible to reduce the tool tip maximum temperature and prolong the tool life.

Wear Properties of Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr Alloys under Different Atmospheres

The study examines the friction and wear properties of Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr alloys under varying gas conditions.The alloy was tested in the presence of oxygen and carbon dioxide using a controlled atmosphere wear tester.The study revealed that the wear environ‐mental embrittlement resulted from the diffusion of reactive atomic hydrogen into the interior of the Ni_(3)Al-Ni_(3)V alloy.The addition of Zr elements decreased the proportion of Al elements on the surface of the Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr alloy and reduced the proportion of H atoms produced by the chemical reaction between atmospheric water vapour and Al elements.This inhibited the environmental embrittlement and improved the performance of the Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr alloy.The wear performance of Ni_(5)Zr alloy is superior to that of Ni_(3)Al-Ni_(3)V.When exposed to air in an air environment,the surface of Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr alloy forms a protective Al_(2)O_(3) oxide film on the workpiece,result‐ing in a reduction of the friction coefficient and wear rate of the alloy.The wear mechanism of the alloy is mainly oxidation wear and abra‐sive wear.In an oxygen environment,the surface of the alloy generates a significant amount of Al_(2)O_(3) oxide film.The flaking of the oxide film leads to an increase in the friction coefficient and wear rate of the alloy.In a carbon dioxide environment,the surface of the alloy un‐dergoes severe deformation,and plough lines become apparent.This is accompanied by flaking Si_(3)N_(4) abrasive chips adhering to the sur‐face of the alloy,which intensifies the wear of the alloy.The primary wear mechanism is abrasive wear.Therefore,the friction coefficient and wear rate of the Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr alloy in the atmosphere are optimal.

TEM Characterization of Self-ion Irradiation Damage in Nickel-base Alloy C-276 at Elevated Temperature

The microstructure of nickel-base alloy C-276 irradiated at 500 ℃ with 300 keY self-ions （Ni^＋） to a peak displacement damage of 4.5 displacements per atom was investigated by transmission electron microscopy. Both black spots and dislocation loops were observed. The black spots were identified as small dislocation loops, with a density of （8.2±0.2）x10^15 cm^-3 and the average loop size of about 15 nm. An increase of dislocation loop density would lead to the increase of the hardness in C-276 alloy, and the increment in yield strength was estimated by the dispersed barrier-hardening model. In [110] orientation, Burgers vectors of the dislocation loops were determined, and it was found that they were predominantly （a/2）〈110〉. In contrast to other nickel-base alloys, no voids were observed in C-276 alloy after being irradiated at elevated temperatures.