Effect Of Rare Earth Addition Research Articles

Effects of rare earth addition and service mode on surface integrity evolution of high-end machine tool spindle bearings under service

Machine tool spindle bearings used as supporting rotator parts play a very important role in machining industry. Keeping a good surface integrity is crucial to the long-time and high-efficiency work of the bearings. To find out the crucial factors for bearing failure, surface integrity evolutions on machine tool spindle bearings made from a normal bearing steel and a newly developed rare-earth-addition bearing steel were compared after benchtop tests in this work. Furthermore, surface integrity evolutions on bearings were analyzed under field service with more complex service conditions. The results show that the surface integrity changes under both benchtop testing and filed service, while the surface damages and changes in surface integrity on the inner rings are more significant than those on the outer rings. Meanwhile, the surface damage modes are mainly scratches and impressions on the benchtop bearings, while surface rolling contact fatigue predominates the damages on the field bearings. Furthermore, the addition of rare earth elements in bearing steels transfers the crack initiation mode from inclusion initiated to martensite initiated under service, possibly resulting in a higher stability of accuracy and longer life for bearings.

Influence of erbium addition on microstructure and performances of AlSi10Mg alloy prepared by selective laser melting

The effect of rare earth addition on the microstructure and mechanical performances of as-cast and wrought Al alloys has been attracting increasing attention recently. Rare earth addition has great potential in modifying the structure and improving the properties of materials. However, there are currently few reports about the effect of rare earth addition on the microstructure and performances of Al alloys prepared via selective laser melting. Here, AlSi10Mg alloys were manufactured using selective laser melting, and the effect of Er addition was investigated. The results indicate that Er addition leads to α-Al refinement and modifies the minority Si phase. The formation of the Al3Er phase induced by Er addition enhances the strength of the material. Modification of the Si phase also increases ductility. This strategy can help improve the mechanical performance of aluminum alloys prepared via selective laser melting.

Effects of rare earth elements addition on mechanical properties and corrosion behavior of GCr15 bearing steel under different heat treatment conditions

In this work, effects of rare earth addition on mechanical properties and corrosion behavior of GCr15 bearing steel under hot rolled, annealed, and quenched-tempered conditions were investigated via mechanical tests, electrochemical measurements, and immersion tests. Results show that rare earth elements can refine grains, improve hardness, tensile strength, and impact absorption energy of GCr15 bearing steel under different heat treatment conditions. Besides, it has been found that rare earth elements are beneficial to corrosion resistance of GCr15 bearing steel in 0.1 mol/L NaCl solution by electrochemical and immersion measurements.

Microstructure and Salt Fog Corrosion of Wrought Mg-Al-Zn and Mg-RE Alloys.

Wrought magnesium alloys have received attention due to their potential application as lightweight materials. However, their use is limited by their poor corrosion resistance. Rare earth additions have the potential to enhance corrosion resistance. The present work included a microstructural investigation and corrosion testing of the alloy WE-43, containing Nd and Y, which was compared against the more conventional compositions of AZ31 and AZ61 alloys. All three alloys exhibited a recrystallized equiaxed structure after hot rolling with the presence of second phases-precipitates. The WE-43 alloy exhibited a better corrosion resistance than AZ31 and AZ61 under salt fog testing, indicated by the lower depth of attack and lower weight loss. The second phases in the microstructure of AZ31 and AZ61 alloys determined their corrosion resistance. The second phases in the AZ31 and AZ61 alloys (based on Al-Mg and Al-Mn phases) were nobler than the Mg matrix and catholically acted, thus sacrificing the Mg matrix. The superior corrosion resistance of WE43 was due to the incorporation of Y in the oxide/hydroxide film. In addition, the second phases in the WE43 consisted of Nd and Y and were less noble than the Mg-matrix. Thus, they acted as anodic sites protecting the Mg-matrix. The above results show the beneficial effect of rare earth additions to wrought Mg alloys towards increased corrosion resistance.

Assessment of the effect of small additions of some rare earth elements on the structure and mechanical properties of castings from hypereutectic chromium white irons

<abstract> <p>Article considers the influence of additions of rare earth elements such as Sm, La, Ce, Nd, and Y on the structure and properties of hypereutectic high-chromium white cast iron of grade G-X300CrMo27-2. To obtain an increased content of carbides in the studied cast iron samples, the carbon content was 3.75–3.9 and 4.1–4.2 wt%. The amount of rare earth elements additives added to the melt is 0.2% by weight. Data were obtained on the effect of overheating and cooling rate in the crystallization interval on the effect of rare earth additives, the structure and properties of white cast iron castings are given. According to the results of the microprobe analysis, it was shown that, under the chosen crystallization conditions, Sm, La, and Ce can form solid solutions with primary and eutectic carbides (FeCr)<sub>7</sub>C<sub>3</sub>. La and Ce form solid solutions with austenite. Nd and Y do not dissolve in iron chromium phases. All listed rare earth elements form phosphides and oxyphosphides. Experimental data are presented on the effect of rare earth elements on the size of primary (FeCr)<sub>7</sub>C<sub>3</sub> carbides and a hypothesis is proposed on the effect of rare earth elements on the crystallization process of hypereutectic chromium white cast irons. Experimental data are presented on the effect of REE additives on the microhardness of phases, hardness, strength, and resistance to abrasive wear of cast iron castings. It was found that the introduction of these additives into hypereutectic chromium white cast iron does not contribute to the modification of the structure and leads to an increase in the size of primary crystals, as well as a decrease in their mechanical properties. However, the addition of Y increases the abrasive wear resistance, but reduces the strength of castings made from such white cast iron.</p> </abstract>

Effect of rare earth addition on corrosion sensitivity of GCr15 bearing steel in marine environment

Recent study demonstrates that only under very low-oxygen conditions can rare earth (RE) play a vital role in improving the performance of RE steels. In this work, the effect of RE addition on marine corrosion of the low-oxygen GCr15 bearing steel has been investigated with the involved mechanisms having been explored. The results indicate that the low-oxygen GCr15 bearing steel exhibits rather low sensitivity to marine corrosion, and the substantially decreased number and size in the inclusions modified by RE addition are responsible for the remarkable performance of the steel. Besides, RE addition has no obvious impact on the structure of GCr15 bearing steel, and the corrosion pits initiate and proceed following the galvanic corrosion mechanism.

Effect of heavy rare-earth (Dy, Tb, Gd) addition on the glass-forming ability and magneto-caloric properties of Fe89Zr7B4 amorphous alloy

In this paper, by adding rare-earth (RE) elements to Fe89Zr7B4 ternary amorphous alloy, we obtained a series of Fe87Zr7B4RE2 (RE = Dy, Tb, Gd) amorphous ribbons to further improve the magnetic refrigeration capacity of the basic alloy. Through the heavy RE element substitutions, the glass-formability of the Fe89Zr7B4 alloy was improved effectively. Besides, the Curie temperature Tc of the alloy system increased from 275 K to 342 K, obtaining a roughly linear correlation between the de Gennes factor and Tc. Through the recombination of ribbons with different Tc values, we designed potential amorphous composites with a "table-like" magnetic entropy change curve under different temperatures. This research promises to deepen understanding of the effect of RE additions on the magneto-caloric properties and enhance the performance of Fe-Zr-B amorphous refrigerants around room temperature.

Effect of rare earth additives on the properties of the PLMN-13PT:RE transparent ceramics

The transparent relaxor ferroelectric ceramics of the system lanthanum modified lead magnesium niobate (PLMN-13PT) have been investigated for a variety of electro-optic, properties; good electro-optic switching times and modest half-wave voltages. In this work, the dependence of microstructural, structural, dielectrical, optical, and electro-optical properties in function of Rare Earth (RE=Tm3+, Nd3+, Yb3+, Er3+ and Ho3+) has been reported. PLMN-13PT:RE with excellent properties were obtained, highlighting the electrical, optical, and electrooptical properties, suitable for the fabrication of multifunctional devices. The most prominent or important feature is the largest quadratic Electro-optic coefficient achieved ((9.37±0.39)×10−16m2/V2) corresponding to PLMN-13PT:Ho transparent ceramics. This result in addition to the electrical and photoluminescence properties becomes a promising alternative to building multifunctional devices.

Effect of Rare Earth Addition on Microstructure, Mechanical Property and Nitriding Performance of a Medium Carbon Steel

Effect of Rare Earth Addition on Microstructure, Mechanical Property and Nitriding Performance of a Medium Carbon Steel

Influence of Rare Earth Additions to an Inconel 718 Alloy

AbstractThis work analyzes the effect of rare earth additions to an Inconel 718 superalloy; for this purpose, two 8 kg ingots of a commercial composition of Inconel 718 were made in a vacuum induction furnace. One of them (In718) with the base composition and the other one (In718RE) with an addition of 0.04wt% of mischmetal (rare earths alloy based on cerium and lanthanum). Both alloys were cast into metallic molds into the vacuum chamber and let to solidify. The alloys were then solubilized for two hours at 1155 °C to eliminate deleterious phases, rolled at 1100 °C to get a reduction of 50% in thickness, then aged for 16 hours at 720 °C and 620 °C by 8 hours each. A complete microstructural characterization was undertaken by optical and electronic (SEM and TEM) microscopy and X-ray diffraction. Mechanical characterization was done by hardness tests, tensile and Charpy impact tests. Results show a slight improvement of the tensile and hardness values for the alloy with rare earth additions. However, no notorious difference was observed during the impact tests, since both alloys show the same values. These mechanical results are discussed in terms of the obtained microstructure. Both alloys are mainly composed by γ, γ´, γ´´ and carbides. It was observed that primary carbides nucleate rare earth particles; therefore, higher number of carbides and of larger size (according to a size distribution) are observed in the alloy with rare earth additions. The presence of such carbides prevents the grain growth during the thermomechanical processing which in turn improve the mechanical properties.

Evaluation of the Effect of Rare Earth Alloying Additions on the Hot Tearing Susceptibility of Aluminum Alloy 7150 During Rapid Solidification

Additive manufacturing of the high-strength 7xxx Al alloy series is limited due to the susceptibility of these alloys to hot tearing. The objective of the current study is to determine the effect of rare earth (RE) element additions on the hot tearing susceptibility of Al alloy 7150 during rapid solidification conditions characteristic of additive manufacturing processes. Cast 7150-xRE (x = 0, 3, 6 wt pct) samples were remelted using a number of laser power-scan speed combinations. Cracks were observed in melt pools for 6 out of 12 processing conditions for 7150, but in all 12 conditions for the RE-containing alloys. Electron backscatter diffraction of the melt pool revealed the melt pool boundary grain size increased with RE additions, and cracks occurred along the grain boundaries. RE-containing intermetallics were observed on the crack surfaces, and were noted to possibly impede the interdendritic flow of eutectic liquids. A smaller amount of eutectic was observed in the thermal data for the RE alloys compared to 7150. Hot tearing indicators were useful in understanding the effect of RE additions when coupled with the experimental results. It is concluded that the addition of 3 to 6 wt pct RE elements increases hot tearing in 7150.

Development of Cerium-Reinforced Specialty Aluminum Alloy with Application of X-ray and Neutron Diffraction

The growing demand for increased power output and efficiency of automobiles has led to the recent effort of improving the high-temperature properties of the currently used powertrain alloys. Research into the effects of rare earth additions, such as cerium (Ce), to aluminum (Al) alloys has been gaining momentum due its high-temperature stability associated with its unique Ce-bearing intermetallics. In this study, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction and neutron diffraction analyses were performed to characterize the microstructure of an Al–6%Ce, Al–16%Ce and an Al–8%Ce–10%Mg alloy. It was observed that the microstructure of the two binary alloys was occupied primarily with fine interconnected Al–Ce eutectic. Additionally, blocky primary Al11Ce3 precipitates were observed in the Al–16%Ce alloy. The large difference in coefficients of thermal expansion between Ce and Al is presumed to be one of the factors leading to the observed extensive microcracking of the primary Al11Ce3 precipitates in the Al–16%Ce alloy and consequently reducing the alloys’ ductility. This reduction in ductility has large implications in terms of usability of the alloy for the targeted powertrain applications. The microstructure of the Al–8%Ce–10%Mg alloy was characterized for the first time and largely consisted of Chinese script or blocky Al11Ce3 precipitates surrounded by a Mg-rich Al matrix. It was found that in addition to solid solution strengthening, the Mg addition may be a factor in altering the fine interconnected Al–Ce eutectic to the coarser Chinese script morphology. This Chinese script morphology is one of the factors restricting dislocations and contributing to the increased strength of the Al–8%Ce–10%Mg alloy at high temperatures, therefore making the alloy suitable for the most demanding engine applications.

Effect of RE Addition on the Solidified Process and Microstructure of Al-7Si-0.3Mg Alloys

The solidification process and microstructure of Al-7Si-0.3Mg alloy with different rare earth (RE) additions have been studied by using thermal analysis, optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The results showed that the addition of RE enhanced the liquidus temperature and decreased the growth temperature of eutectic Si, which lead to obvious increase in solidification interval of the studied alloy. In addition, the grain size of primary α-Al had no obvious change, and the mean area of eutectic Si particles decreased with increasing RE content to 1.6 wt.%. The RE-rich compounds with different compositions were obtained with increasing RE concentration in Al-7Si-0.3Mg alloys. The method of phase diagram calculation helps to clarify the formation and growth mechamism of different RE-rich phases during solidification.

The Effect of Rare Earth Addition on Microstructure and Mechanical Properties of the Rapidly Solidified Al-Si And Al-Si-Ni Alloys

The Effect of Rare Earth Addition on Microstructure and Mechanical Properties of the Rapidly Solidified Al-Si And Al-Si-Ni Alloys

Effect of rare earth addition on [formula omitted] twinning induced hardening in magnesium

We investigated the effect of Gd and Ce additions in magnesium on sigmoidal hardening behavior associated with {101̅2} twinning after extrusion. Compression along extrusion direction revealed that rare earth additions enhance the flow stress, while 〈c+a〉 softening was expected. This phenomenon has been explained by the enhancement of 〈c+a〉 dislocations activity and the ensuing increase in forest hardening due to solute drag. It is expected that dislocation transmutation of basal to prismatic will be enhanced during {101̅2} twin growth in rare earth containing alloys, which would exacerbate 〈c+a〉 entanglement with the dislocation forests inside the twins. Forest hardening events overcompensated for the softening effects from lowering the critical resolved shear stresses of 〈c+a〉 dislocations, and resulted in higher flow stress for the binary rare earth containing alloys.

Effect of rare earth addition on solidification characteristics and microstructure of ZRE1 magnesium cast alloy

The thermal parameters of ZRE1 cast alloy with 1.0 wt.% of praseodymium (Pr) and 1.0 wt.% of erbium (Er) were evaluated by the computer-aided cooling curve thermal analysis (CA-CCTA), whereas the microstructure analysis was investigated by the optical microscope and field emission scanning electron microscopy. The results of the cooling curve and microstructure analyses showed that Pr and Er reduced the grain size. The thermal analysis result recorded a faster freezing time and lower solidification temperature with Pr and Er additions and 15.5 and 11.2% decrease in the grain size, respectively. Scanning electron microscopy results showed that Er formed a granular particles of Er-containing phases existed in the α-Mg matrix, while Pr formed Mg–Zn–Pr–Ce phase with secondary phase which distributed along the grain boundaries.

Effect of rare earth addition on the heterogeneous nucleation behavior of TiN in duplex stainless steel

The effect of rare earth addition on the heterogeneous nucleation behavior of TiN was investigated by analyzing inclusions behaviors in a commercial duplex stainless steel. The results showed that the rare earth oxides and oxysulfides could induce the precipitation of fine TiN particles to form the composite TiN (TiN + cores) with a size less than 4 µm. It was found that TiN was more likely to precipitate on the rare earth oxides than rare earth oxysulfides, the number of composite TiN with rare earth oxides core was larger than composite TiN with a rare earth oxysulfides core. In addition, more than 60% rare earth oxides were completely surrounded by TiN, further indicating that rare earth oxide was favor to induce the precipitation of TiN. When a [Ti] and a [Ce] met the relationship of 1g a[Ti] O3 could stably form to promote the precipitation of fine TiN particles. Decreasing the sulphur content of steel was an efficient way to form Ce2 O3 and suppress the formation of Ce2 O2 S.

Effect of rare earth addition on microstructure and corrosion behavior of plasma nitrocarburized M50NiL steel

M50NiL steel was plasma nitrocarburized at 480 °C with and without rare earth (RE) addition. The microstructures of the surface layer were characterized by optical microscopy, X-ray diffraction and scanning electron microscopy. The mechanical properties and corrosion resistances of the surface layer were studied by Vickers microhardness measurements and polarization tests in 3.5% NaCl solution. The results showed that RE atoms could diffuse into the surface layer of the steel and inhabit the formation of ε-Fe2–3(N,C) phase. As compared to the treatment without RE addition, RE addition further increased the surface hardness by 143 HV0.1, and further increased the thickness of the nitrocarburized layer by 39 μm. Compared with the quenched bearing steel, the corrosion resistance of the samples nitrocarburized with and without RE addition could be significantly improved. Especially, the sample plasma nitrocarburized with RE addition exhibited the highest corrosion resistance.

Effect of rare earth addition on diffusion kinetics of borided TC21-DT titanium alloy

In this study, the properties and growth kinetics of boride layers, generated on the surface of TC21-DT alloy using appropriate amount of powders of boron carbide (B4C) and rare earth oxide (CeO2) were investigated. By conducting a series of experiments at different temperatures of 1123, 1223 and 1273 K for periods up to 10 h, the effects of rare earth (RE) addition on the growth kinetics of boride layers were studied. The characteristics of the boride layers were examined by scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction and micro-Vickers hardness tester. The results showed that the boron diffusion in boride layers was obviously accelerated by RE addition and the activation energy for RE addition-boriding in TC21-DT alloy was greatly decreased to 58.13kJ/mol, which was approximately 40% lower than that of conventional one, without RE addition.

Effect of Rare Earth Additives on the Catalytic Performance of Rh/ZrO2 Three-Way Catalyst

The catalytic activity of Rh/ZrO2 for NO–CO–C3H6–O2 reaction under stoichiometric conditions was significantly improved by addition of rare earth. Among the catalysts tested here, Y-doped Rh/ZrO2 (Rh/Y/ZrO2) showed the highest three-way catalytic performance. The catalytic activity of rare earth-doped Rh/ZrO2 was strongly related to the Rh dispersion, which was improved by using rare earth-doped ZrO2 with large amount of surface basic sites. The role of rare earth additive was considered to control the surface basicity of ZrO2 and stabilize the Rh species in high dispersion state. Y-stabilized ZrO2 was found to be effective support for Rh catalyst in NO–CO–C3H6–O2 reaction. The site geometry and the surface electric state of Rh can be altered by interacting with Y2O3, leading us to consideration that the presence of suitable Rh–Y2O3 interaction is responsible for high NO reduction activity of Rh/Y–ZrO2.