Effect of hydrogen peroxide concentration on surface properties of Ni-Cr alloys

The effect of concentration of hydrogen peroxide （H2O2） on the surface properties of Ni-Cr alloys was studied. Surface roughness and surface morphology of Ni-Cr alloys were evaluated by surface profiler and scanning electron microscopy after being immersed in different concentrations of H2O2 for 112 h. Surface corrosion products of Ni-Cr alloys were analyzed by photoelectron spectrograph after being immersed in 0% and 30% H2O2. The order of increasing surface roughness of Ni-Cr alloys after being immersed in different concentrations of H2O2 was 0〈3.6%〈10%〈30%. As the concentration of hydrogen peroxide increased, the surface roughness of Ni-Cr alloys increased and the surface morphology showed different degrees of corrosion. According to the XPS results, the corrosion products formed on the outmost surface layer of the studied samples are Ni（OH）2 and BeO.

Density of Liquid Ni-Cr Alloy

The density of liquid Ni-Cr alloy was measured by a modified sessile drop method. The density of liquid Ni-Cr alloywas found to decrease with increasing temperature and Cr concentration in the alloy. The molar volume of liquidNi-Cr alloy increases with increasing the Cr concentration in the alloy. The molar volume of Ni-Cr alloy determinedin the present work shows a positive deviation from the linear molar volume.

Ni-Cr alloy electrodepositing technology on Fe substrate and coating performance

The Ni-Cr alloy electrodepositing technology on iron substrate in the chlorid-sulfate solution and the impacts of main processing parameters on coating composition were studied. The optimal Ni-Cr alloy electrodepositing conditions are that the cathode current density is 16 A/dm^2,the plating solution temperature is 30℃ and the pH value is 2.5. The bright, compact coating gained under the optimal conditions has good cohesion and 24.1% Cr content. The results show that the coating is composed of crystalline, the average grain size is 82 nm and the higher the Cr content of coating, the larger the rigidity, and the higher the corrosion resistance. The rigidity of coating reaches 78.6(HR30T) and the passivation area broadens to 1.4 V when the Cr content of coating is 24.1%.

Density of Ni-Cr Alloy in the Mushy State

The density of Ni-Cr alloy in the mushy state has been measured using the modified sessile drop method. The density of Ni-Cr alloy in the mushy state was found to decrease with increasing temperature and Cr concentration in alloy. The molar volume of Ni-Cr alloy in the mushy state therefore increases with increasing the Cr concentration in alloy. The ratio of the difference of density divided by the temperature difference between liquidus and solidus temperatures decreases with increasing Cr concentration. The density of the alloy increased with the precipitation of a solid phase in alloy during the solidification process. The temperature dependence of the density of alloy in the mushy state was not linear but biquadratic.

The Effect of Argon Inert Gas on the Laser Welding Quality of Co-Cr and Ni-Cr Base Metal Alloys

The purpose of this research was to study the effect of Argon inert gas on the laser welding quality of Co-Cr and Ni-Cr base metal alloys, which are widely used as Fixed Prosthodontics alloys in Dental Laboratories. A total of 36 specimens were manufactured (18 of Ni-Cr alloy and 18 of Co-Cr alloy). The specimens were then divided into 3 subgroups (6 specimens each): control;argon-welded;and non-Argon welded. The specimens were cut, laser welded, radiographed and finally tested under tensile strength testing, followed by examination using Scanning Electron Microscopy. The tensile strength of welded specimens was lower than the strength of non-welded specimens, however this difference was not found to be statistically significant. The material factor (Co-Cr alloy or Ni-Cr alloy) has a statistically significant effect on the tensile strength, while the presence or not of the inert gas, as well as the combination of the two factors do not have a statistically significant effect. The laser welding process applied in daily practice (separation of specimen, formation of two cones in contact, aggregation of two cones, filling of the remaining gap by welding) is considered satisfactory in terms of weld strength. The factor of the material, as an independent factor, affects the tensile strength to a statistically significant degree, in contrast to the factor of the presence of inert gas which does not affect to a statistically significant degree.

Microstructure and Wear Resistance of Ni-Cr Alloy Laser Cladding Layer with High Cr Content

Four kinds of Ni-xCr alloy laser cladding layers(x=20,40,60 and 80,wt%)were prepared by high-speed laser cladding technique,and the relationship between microstructure and wear resistance of Ni-Cr alloy laser cladding layers with different Cr contents was investigated.The results show that the four Ni-Cr alloy laser cladding layers all have reticulated dendritic structures.Among them,Ni-20Cr and Ni-40Cr are single-phaseγ-(Ni,Cr)solid solutions,and their wear mechanisms are adhesive wear and abrasive wear.With the increase in Cr content,Ni-60Cr and Ni-80Cr areγ-(Ni,Cr)phase and Cr phase,as well as Cr-rich precipitates,and their wear mechanisms are adhesive wear,abrasive wear and fatigue wear.A moderate increase in Cr content can enhance the hardness and wear resistance of Ni-Cr alloy laser cladding layer.However,excessive addition of Cr results in the precipitation of Cr-rich precipitates.The hardness of these precipitates is 2430.4 MPa,which is lower than the hardness of the Ni-60Cr matrix(4024.86 MPa)and Ni-80Cr matrix(7022.68 MPa).A hardness transition zone exists between the Cr-rich precipitates and the matrix.Cracks are likely to initiate and expand in this zone,leading to deep spalling,which is not conducive to the wear-resistant properties of the laser cladding layer.Ni-80Cr has the highest hardness,but its high Cr content leads to a large number of penetrating cracks and Cr-rich precipitates on the surface,ultimately resulting in the worst wear resistance.Ni-60Cr exhibits the best wear resistance due to its high hardness and dense microstructure.

向NI-Cr合金中添加Ni/C制备自润滑金刚石工具（英文）

利用添加3%、5%的Ni-Cr合金在保护气氛炉中制备金刚石试样,钎焊温度为1 050℃,保温5 min。采用扫描电镜分析钎焊金刚石形貌和钎缝的微观组织,维氏硬度计测量接头的硬度。结果表明:添加Ni/C的Ni-Cr合金对金刚石具有较好的润湿性,可以实现高强度连接,碳化物在金刚石表面形核和结晶长大,与金刚石表面的原子分布具有一定位向关系。钎缝中形成的空心Cr7C3和簇状共晶石墨与添加的Ni/C有关,钎焊层中有少量Ni/C剩余,硬度从830HV0.2降低到700HV0.2,这有利于降低钎焊热应力和金刚石后期的出露高度。

不同金属材料PFM影响牙龈的相关研究

目的:研究不同金属烤瓷全冠在临床中对牙龈的影响。方法:在患者自愿配合研究的基础上选取136颗基牙分为四组进行PFM修复,A组PFM修复中所用金属材料为钴铬合金,B组所用为金钯合金,C组所用为钛合金,D组选用钯银合金。修复前及修复后3个月、6个月、12个月对受试者进行临床检查,项目包括检测菌斑指数、AST水平、牙龈指数。结果:A、C、D组患者修复后各时间段的检测指标与修复前比较无显著差异(P>0.05),B组患者在修复后12个月时菌斑指数、AST水平、及牙根指数与修复前及B组均具有显著差异(P<0.05)。结论:金钯合金烤瓷全冠较其他合金烤瓷全冠对牙周组织的损伤更小,有利于牙龈的健康及修复体使用寿命的延长。

后牙金铂合金全金属颈环PFM的临床观察

目的观察后牙金铂合金全金属颈环烤瓷熔附金属全冠(PFM)边缘适合性以及对牙龈健康的影响。方法对134颗后牙烤瓷熔附金属全冠(单冠或桥的基牙)修复2年后观察其边缘适合性以及牙龈健康状况的临床情况。结果后牙金铂合金全金属颈环PFM的边缘适合性以及牙龈健康状况均好。结论后牙金铂合金全金属颈环烤瓷熔附金属全冠(PFM)是一种好的设计,建议作为临床常规设计。

Comparison of Clinical Effects of Au-Pt Based and Ni-Cr Based Porcelain Crowns

Objective To compare the long-term clinical effects of two kinds of crowns and bridges made of porcelain fused to Au-Pt alloy and Ni-Cr alloy. Methods A total of 131 teeth (64 patients) were rehabilitated using porcelain-fused-to-metal crowns, among which 59 were rehabilitated with Au-Pt alloy metal ceramic crown and 72 with Ni-Cr alloy metal ceramic crown. The porcelain fracture, shade, marginal adaptation, gingival discoloration, and gingival status after finishing restoration and 36 months of follow-up were evaluated. Results After 36 months of restoration, porcelain fused to Au-Pt alloy crown showed better clinical effects than porcelain fused to Ni-Cr alloy crown in shade, marginal adaptation, gingival discoloration, as well as gingival status (all P<0.05). Conclusion The Au-Pt alloy ceramic crown is superior to Ni-Cr alloy ceramic crown in long-term clinical effects.

Tribological property and high temperature oxidation behavior of Ni-based alloy

Ni-Cr based alloys were prepared by hot-pressing the mixture of strengthening phases Mo, Al, Ti, and lubricant phase MoS2. The hardness, tribological properties as well as the high temperature oxidation properties were evaluated, The results show that the strengthening phases can improve the mechanical properties of Ni-Cr based alloy obviously, and the wear and friction properties of Ni-based alloy with strengthening phase can be improved. Its friction coefficient and wear rate rubbed with Al2O3 ceramic disk are about 0.4 and 10 -14m3/（N·m）, respectively, and the oxidation process is mainly affected by Cr2O3.

668颗后牙镍铬合金PFM边缘适合性的临床观察

目的:观察采用2种边缘形式的后牙烤瓷熔附金属全冠边缘适合性和对牙龈健康的影响。方法:对668颗后牙,分别采用2种边缘形式的后牙烤瓷熔附金属全冠(单冠或桥的基牙)在修复2年后进行复查,检测其边缘适合性及牙龈指数(GI)和牙周探诊深度(PD),用统计学方法分析修复体边缘形式与牙龈病变间的关系。结果:采用羽状边缘360°金属脚边的PFM边缘适合性明显优于凹面肩台型边缘PFM,凹面肩台型边缘的PFM的牙龈病变发生率,明显高于羽状边缘360°金属脚边的PFM,而边缘适合性差者较适合性好者牙龈病变发生率显著增高。结论:后牙PFM的边缘采用羽状边缘360°金属脚边是一种好的选择。

Effect of Rare Earth Elements on Thermal Fatigue of High Ni－Cr Alloy Cast Iron

The effect of RE on crack forming and developing of hot rolled high Ni-Cr alloy cast iron during thermal fatigue test was investigated.It shows that the serviceable life of hot rolled high Ni-Cr alloy cast iron can be improved by RE.The number of cycle before fracture was increased by 42%～163%.The optimum of RE addition is 0.05 wt%～0.15wt%.

Short-range ordering plays a determining role in the low-cycle fatigue life improvement of fcc metals: A conclusive study on low solid-solution hardening Ni-Cr alloys

The effect of short-range ordering (SRO) on the low-cycle fatigue (LCF) behavior of low solid-solution hardening Ni-Cr alloys with high stacking fault energies (SFEs) was systematically studied under cycling at constant total strain amplitude (Δε t /2) in the range of 0.1%–0.7%. The results show that an inducement of SRO structures can notably improve the fatigue life of the alloy regardless of Δε t /2, and several unique fatigue characteristics have been detected, including the transition of fatigue cracking mode from intergranular cracking to slip band cracking, the non-negligible evolution from non-Masing behavior in pure Ni to Masing behavior in the Ni-40Cr alloy, and the secondary cyclic hardening behavior in the Ni-10Cr and Ni-20Cr alloys. All these experimental phenomena are tightly associated with the transformation in cyclic deformation mechanisms that is induced by SRO based on the “glide plane softening” effect. Furthermore, a comprehensive fatigue life prediction model based on total hysteresis energy has been reasonably proposed, focusing on the analyses of the macroscopic model parameters (namely the fatigue cracking resistance exponent β and the crack propagation resistance parameter W 0 ) and microscopic damage mechanisms. In brief, on the premise that the effects of SFE and friction stress can be nearly ignored, as in the case of the present low solid-solution hardening Ni-Cr alloys with high SFEs, an enhancement of SRO in face-centered cubic metals has been convincingly confirmed to be an effective strategy to improve their LCF performance.

钴铬合金和金合金烤瓷全冠修复对龈沟液中AST、ALP、TNF-α和IL-8、GP-x、MDA水平的影响

目的:探讨钴铬合金和金合金烤瓷全冠修复对龈沟液(GCF)中天冬氨酸转氨酶(AST)、碱性磷酸酶(ALP)、肿瘤坏死因子-α(TNF-α)和白细胞介素-8(IL-8)、谷胱甘肽过氧化物酶(GP-x)、丙二醛(MDA)水平的影响。方法:选择在我院收治的80例单个上颌前牙烤瓷全冠修复的患者分为钴铬合金组和金合金组各40例,分别采用钴铬合金和金合金全冠修复。两组均于烤瓷熔附金属全冠(PFM)修复前和修复后6个月时检测牙龈指数(GI)、牙周袋探诊深度(PD)和GCF量,并检测GCF中AST、ALP、TNF-α、IL-8、GP-x及MDA水平。结果:两组修复前GCF量、GI及PD比较,差异均无统计学意义(P>0.05);两组修复后GCF量、GI及PD均明显高于修复前,然而金合金组GCF量、GI及PD均明显低于钴铬合金组,差异具有统计学意义(P<0.05)。两组修复前GCF中AST、ALP、TNF-α、IL-8、GP-x及MDA水平比较,差异均无统计学意义(P>0.05);两组修复后GCF中AST、ALP、TNF-α、IL-8及MDA水平均明显高于修复前,然而金合金组GCF中AST、ALP、TNF-α、IL-8及MDA水平均明显低于钴铬合金组,差异具有统计学意义(P<0.05)。两组修复后GCF中GP-x水平均明显低于修复前,然而金合金组GCF中GP-x水平明显高于钴铬合金组,差异均具有统计学意义(P<0.05)。结论:金合金相比于钴铬合金能够明显降低龈沟液中AST、ALP、TNF-α、IL-8及MDA水平、提高龈沟液中GP-x水平,对牙龈的刺激性较轻,具有较好的生物相容性,临床效果较好。

Captek基底对烤瓷修复体颜色影响的实验研究

目的 :研究Captek基底对烤瓷修复体颜色的影响 .方法 :采用CIE1 976L a b 比色系统比较了Captek、贵金属合金、镍铬合金 3种基底合金对烤瓷修复体颜色的影响 ,采用两种瓷粉 (Ivoclar瓷粉 ,Ceramco瓷粉 )制作的无基底的全层瓷片做对照组 .结果 :使用Ivoclar瓷粉 3个实验组与对照组色差值分别为 :(0 .78± 0 .2 6 ) ,(0 .6 9± 0 .2 5 ) ,(1 .30±0 .31 ) ;使用Ceramco瓷粉 3个实验组与对照组色差值分别为 :(1 .4 3± 0 .78) ,(1 .2 9± 0 .78) ,(4 .1 8± 1 .37) .ΔECaptek/Ni Cr,ΔENi Cr/PentronBio86均大于 1 .5NBS .结论 :Captek基底对烤瓷修复体颜色无影响 ,可以较理想地复现选定的颜色 .

不同齿科铸造合金电化学腐蚀的观测研究

目的:研究不同牙科铸造合金或合金的不同处理形式对合金耐腐蚀性能的影响,为临床烤瓷合金的选择提供依据。方法:(1)采用铸造方法分别制作普通镍铬合金、镍铬合金镀金及金合金试样各8个,在人工唾液中测定各试样的极化曲线。(2)对临床采用上述3种合金烤瓷冠修复的735例病例,在修复1年后,分组对临床观察效果进行统计分析。结果:(1)镍铬合金试件和镀金试件,两次的阳极极化曲线皆有明显差异;贵金属试件,极化曲线的斜率和低腐蚀区宽度均无明显变化。(2)修复体戴用1年后,镍铬合金与镍铬合金镀金烤瓷的牙龈指数差异有显著性(P<0.05),而镀金与贵金属烤瓷修复体的牙龈指数差异无显著性(P<0.05);3组病例的菌斑指数在1年内差异均无显著性(P<0.05);镍铬合金烤瓷修复体牙龈退缩的比率明显高于其他2组(P<0.05),而镀金与贵金属烤瓷修复体牙龈退缩的比率无明显差别(P<0.05)。结论:应用极化曲线可以分析金属的表面状态,从而确定金属在何种情况下耐腐蚀性更好。就耐腐蚀性而言,贵金属合金最优,镀金次之,普通烤瓷合金最差。镀金试件镀层不全可造成合金更易受腐蚀,但随着时间的延长,其耐腐蚀能力增强。

3种烤瓷铸造合金的离子析出研究

目的研究3种常用烤瓷非贵金属合金模拟烤瓷前、后在体外细胞培养液中离子析出的量及种类。方法用失蜡法铸造3种常用烤瓷非贵金属合金试件,镍铬合金、钴铬合金、镍钛合金,置于DMEM体外细胞培养液中30 d后重新打磨,模拟烤瓷加热过程,之后放回DMEM体外细胞培养液中浸泡30 d,用电感耦合等离子发射光谱法(ICP-AES)观察烤瓷处理前、后3种合金离子的析出的改变,扫描电镜(SEM)对表面形态观察。结果 (1)3种合金离子析出总量依次为镍铬合金>钴铬合金>镍钛合金,(2)模拟烤瓷程序后3种合金离子析出总量减少,差异具有统计学意义(P<0.05)。结论 3种常用烤瓷非贵金属合金中,镍铬合金的离子析出量最大,生物相容性最差;烤瓷过程会促进这3种合金表面氧化膜的生成,使合金的耐腐蚀性有所增强。

二种金属烤瓷冠对基牙龈沟液量及其成分的影响

目的探讨二种金属烤瓷冠(PFM)对基牙龈沟液(GCF)量、龈沟液中的天冬氨酸转氨酶(AST)和碱性磷酸酶(ALP)水平的影响。方法选择双侧上颌第一磨牙均需修复的患者39例,每例双侧上颌第一磨牙随机分别行钛合金和金合金PFM修复,分别于修复前、修复后1周、1月和6月检测GCF量、GCF-AST和GCF-ALP活性水平三项指标。结果2组实验牙修复前三项指标接近(P>0.05),修复后1周、1月和6月钛合金PFM组的三项指标较修复前增加(P<0.01),并高于同期金合金PFM组(P<0.05),且修复后1～6月GCF-AST、GCF-ALP水平呈现递增趋势(P<0.05);相反金合金PFM组则随时间的推移较修复前无明显改变(P>0.05)。结论金合金PFM是一种较钛合金PFM对牙周组织健康影响更小的修复体。

浸渗法合金化纯钨表层的研究

采用浸渗Ni-Fe熔体法,使纯钨形成一定深度的W-Ni-Fe合金化表层,研究不同浸渗时间下合金化表层的深度变化与显微组织特征。结果表明:浸渗10～40min对应的合金化表层均由W相与含一定W原子的富Ni-Fe黏结相构成。浸渗10min和20min时,对应的合金化表层深530μm和700μm,黏结相非常细小,且分散嵌于W相之间;浸渗30min和40min时,对应的合金化表层深750μm和770μm,在深约60μm的浅表内,黏结相明显增大,部分W相呈圆滑颗粒态。结合实验结果及W-Ni二元合金相图,分析了合金化表层的形成机制。