激光焊接新型钴铬合金的力学性能

背景：新型钴铬合金为一种不含镍和铍等有害成分的齿科合金材料,但关于其激光焊接的研究尚未见报道。目的：分析新型钴铬合金的激光焊接参数,优选激光焊接电压条件。方法：铸造0.5mm×6mm×30mm的新型钴铬合金试件60个,将试件分成6组。1组作为对照组;5组试件从中间断开,进行激光焊接,光斑直径设定为0.6mm,脉冲持续时间10ms,电压分别为220,250,280,310,340V,焊后进行拉伸强度测试,记录拉伸强度和延伸率。结果与结论：激光焊接新型钴铬合金拉伸强度随电压升高而增加。延伸率在电压低于280V时,随电压增大而增加;高于280V时,随电压增大而降低。电压为280V时,激光焊接新型钴铬合金的拉伸强度为（679.94±46.87）MPa,延伸率为（5.91±0.38）%。提示电压280V,脉冲持续时间10ms,光斑直径0.6mm条件下激光焊接新型钴铬合金的拉伸强度和延伸率均能满足临床要求。     

新型钴铬合金与高金合金边缘适合性和金瓷结合强度的比较

背景：钴铬合金不含镍和铍等有害元素,且增加了钼和硅的含量,被认为适宜烤瓷使用,但关于其边缘适合性和金瓷结合性能等方面均未见相关报道。目的：比较高金合金和新型钴铬合金烤瓷冠边缘适合性和金瓷的结合强度。方法：金瓷冠预备体可卸代型24个,分为两组,一组为高金合金组,一组为新型钴铬合金组,分别制作金合金和新型钴铬合金基底烤瓷冠各12个,羧酸锌水门汀黏固。应用体式显微镜测量边缘浮出量,后将样本置于自制套管内,采用万能拉伸实验机测量崩瓷时的载荷力值。结果与结论：高金合金组唇侧边缘间隙、舌侧间隙均稍高于新型钴铬合金组,但差异均无显著性意义（P〉0.05）,崩瓷时的载荷力值稍低于新型钴铬合金组,但差异无显著性意义（P〉0.05）。说明从边缘适合性和金瓷结合角度来看,新型钴铬合金较适合烤瓷用。     

新型钴铬合金与高金合金边缘适合性和金瓷结合强度的比较

背景:钴铬合金不含镍和铍等有害元素,且增加了钼和硅的含量,被认为适宜烤瓷使用,但关于其边缘适合性和金瓷结合性能等方面均未见相关报道。目的:比较高金合金和新型钴铬合金烤瓷冠边缘适合性和金瓷的结合强度。方法:金瓷冠预备体可卸代型24个,分为两组,一组为高金合金组,一组为新型钴铬合金组,分别制作金合金和新型钴铬合金基底烤瓷冠各12个,羧酸锌水门汀黏固。应用体式显微镜测量边缘浮出量,后将样本置于自制套管内,采用万能拉伸实验机测量崩瓷时的载荷力值。结果与结论:高金合金组唇侧边缘间隙、舌侧间隙均稍高于新型钴铬合金组,但差异均无显著性意义(P>0.05),崩瓷时的载荷力值稍低于新型钴铬合金组,但差异无显著性意义(P>0.05)。说明从边缘适合性和金瓷结合角度来看,新型钴铬合金较适合烤瓷用。     

自制钴铬烤瓷合金的金瓷结合性能

背景:在非贵金属烤瓷合金中,钴铬烤瓷合金在生物相容性、耐腐蚀性以及金属稳定性方面都优于镍铬烤瓷合金和含钛烤瓷合金,被广泛的应用于临床.目的:通过与德国BEGO 钴铬合金对比,评价自制钴铬烤瓷合金的金瓷结合性能.方法:制作25 mm×3 mm×0.5 mm规格的德国BEGO 钴铬合金与自制钴铬烤瓷合金两种合金的金属试条,分别熔附8 mm×3 mm×1 mm的VITA MK 95 瓷粉,采用三点弯曲的方法测试金瓷结合力,利用扫描电镜观察金属氧化界面.结果与结论:加力后国产和德国BEGO 钴铬合金样本随着力量的增加瓷层开裂同时完全脱落,表面成灰黑色氧化膜,无明显瓷残余;自制钴铬烤瓷合金与德国BEGO 钴铬合金的金瓷结合力差异无显著性意义[(41.26±2.68),(41.35±2.59) MPa,P > 0.05].说明自制钴铬烤瓷合金的金瓷结合强度高于ISO 所要求的基本值25 MPa,且与德国BEGO 钴铬合金相比无差异,可满足临床要求.     

自制钴铬烤瓷合金的金瓷结合性能

背景：在非贵金属烤瓷合金中,钴铬烤瓷合金在生物相容性、耐腐蚀性以及金属稳定性方面都优于镍铬烤瓷合金和含钛烤瓷合金,被广泛的应用于临床。目的：通过与德国BEGO钴铬合金对比,评价自制钴铬烤瓷合金的金瓷结合性能。方法：制作25mm×3mm×0.5mm规格的德国BEGO钴铬合金与自制钴铬烤瓷合金两种合金的金属试条,分别熔附8mm×3mm×1mm的VITAMK95瓷粉,采用三点弯曲的方法测试金瓷结合力,利用扫描电镜观察金属氧化界面。结果与结论：加力后国产和德国BEGO钴铬合金样本随着力量的增加瓷层开裂同时完全脱落,表面成灰黑色氧化膜,无明显瓷残余;自制钴铬烤瓷合金与德国BEGO钴铬合金的金瓷结合力差异无显著性意义[（41.26±2.68）,（41.35±2.59）MPa,P〉0.05]。说明自制钴铬烤瓷合金的金瓷结合强度高于ISO所要求的基本值25MPa,且与德国BEGO钴铬合金相比无差异,可满足临床要求。     

反复熔铸影响新旧钴铬烤瓷合金的机械性能

背景：目前关于反复铸造后钴铬烤瓷合金机械性能改变的研究已有较多研究报道,而对于将回收旧料再利用于新料中后再铸造钴铬烤瓷合金机械性能的研究则少有报道。
　　目的：研究反复熔铸对不同比例新旧钴铬烤瓷合金拉伸强度、屈服强度、延伸率及显微硬度等机械性能的影响。
　　方法：由新钴铬烤瓷合金熔铸成Ⅰ代铸件,40%Ⅰ代废旧料添加60%新钴铬烤瓷合金熔铸成Ⅱ代铸件,40%Ⅱ代废旧料添加60%新钴铬烤瓷合金熔铸成Ⅲ代铸件,40%Ⅲ代废旧料添加60%新钴铬烤瓷合金熔铸成第Ⅳ代铸件。采用拉伸实验测试各代试件的拉伸强度、0.2%屈服强度、延伸率;采用弯曲实验测试各代试件的弯曲强度;采用硬度实验测试各代试件的维氏硬度值;并进行显微金相观察。
　　结果与结论：Ⅱ,Ⅲ,Ⅳ代铸件拉伸强度、0.2%屈服强度、延伸率、弯曲强度及维氏硬度值与Ⅰ代铸件比较,差异均无显著性意义。Ⅰ代试样晶粒的大小均匀一致,直径较小,沿晶界分布的碳化物大小也较均匀细小,主要呈球形和不规则的蠕虫状两种形态;Ⅱ代和Ⅲ代试样组织形态尚均匀,只是晶粒有些粗化;Ⅳ代试样显微组织中的碳化物开始粗化,不规则蠕虫状的碳化物含量增多,可发现晶粒内存在少量非金属夹杂物。表明新旧比例为3∶2的钴铬烤瓷合金至少可以反复熔铸3次而不引起机械性能下降。     

钴铬合金及银钯合金烤瓷冠对牙周组织的影响*

背景:金属烤瓷全冠是修复牙体缺损的最常用方法,牙周问题是导致修复失败的最常见原因.目的:评价钴铬合金和银钯合金作为烤瓷冠内冠材料对牙周组织的影响.方法:选择采用钴铬合金和银钯合金烤瓷冠修复患者75例,189颗患牙,其中106颗采用钯合金烤瓷冠修复体,83颗应用钴铬合金修复体.于修复前后临床对比患牙龈沟出血指数、龈沟液量、龈沟液中与炎症相关的细胞因子白细胞介素1β和肿瘤坏死因子α浓度,以及龈沟液中牙龈卟啉单胞菌、伴放线嗜血杆菌、福赛斯坦纳菌等3种细菌检出率的变化.结果与结论:①与修复前比较,钴铬合金烤瓷冠修复12个月后,患牙龈沟出血指数和龈沟液量、龈沟液中细胞因子白细胞介素1β、肿瘤坏死因子α水平及龈沟液中牙龈卟啉单胞菌、福赛斯坦纳菌检出率升高(P <0.05或P﹤0.01),伴放线嗜血杆菌检出率无明显变化(P >0.05).②与修复前比较,银钯合金烤瓷冠修复12个月后,龈沟出血指数和龈沟液量升高(P <0.05),龈沟液中细胞因子白细胞介素1β、肿瘤坏死因子α水平及3种细菌检出率无明显变化(P >0.05).表明两种材料的烤瓷冠对患牙牙周组织均有影响,其中银钯合金影响较小,钴铬合金影响较大.     

氯离子对两种钴铬合金修复体离子析出行为的影响

目的:研究激光快速成形技术钴铬合金及铸造钴铬合金试件在不同氯离子浓度人工唾液中的离子析出行为。方法:采用激光快速成形技术制备钴铬合金试件24块,并以同种成分的铸造钴铬合金试件作对比,每种试件分为三组,分别浸泡于0.9%、2.0%及3.0%氯化钠浓度的人工唾液中,于第7、14、21、28、35、42、49、56天时检测人工唾液中试件的钴、铬离子析出浓度。结果:同种方法成形的试件,随着氯离子浓度升高,样本中的钴、铬离子析出量也增高,3.0%Na Cl浓度组离子析出量高于2.0%和0.9%Na Cl组,差异有统计学意义(P0.05);氯离子浓度相同的人工唾液中,各时间点的激光快速成形技术钴铬合金离子析出量均低于铸造钴铬合金,在2.0%和3.0%Na Cl浓度时差异有统计学意义(P0.05);随着时间的延长(前4周),2种钴铬合金的离子析出量逐渐增加,差异有统计学意义(P0.05)。结论:激光快速成形技术钴铬合金的抗腐蚀性能优于铸造钴铭合金。     

选择性激光熔覆技术与失蜡铸造法制作的钴铬合金基底冠的边缘适应性的比较

目的：比较选择性激光熔覆技术（selective laser melting,SLM）与传统失蜡铸造法制作的钴铬合金基底冠的边缘适应性的差异.方法：采用SLM技术与失蜡铸造法在统一规格的模型上各制作钴铬合金基底冠20个,采用扫描电镜检测钴铬合金基底冠的边缘密合性.结果：传统失蜡铸造法制作组基底冠的边缘密合性明显低于SLM组（P＜0.05）.结论：SLM可以增加钴铬合金基底冠的边缘适应性,使基底冠具有更好的密合度,达到更好的临床修复效果.     

钴铬合金烤瓷全冠修复的护理配合

随着口腔修复材料与工艺技术的不断发展,用于替代传统金属烤瓷冠的方法也不断被应用,钴铬合金烤瓷冠具有良好的边缘封闭性和良好的生物相容性,色泽美观自然、操作简单、制作精良、价格相对较低,故具有较高的临床应用价值。我科于2005年1月～2006年12月为44例患者进行了钴铬合金烤瓷全冠修复,现将其护理配合总结如下。     

Aorta and skin tissues welded by near-infrared Cr4+:YAG laser

OBJECTIVE: The aim of our study was to explore the wavelength dependence of welding efficacy. Ex vivo samples of human and porcine aorta and skin tissues were investigated using a tunable Cr(4+):yttrium aluminum garnet (YAG) laser. BACKGROUND DATA: Tissue welding is possible using laser light in the NIR spectral range. Collagen bonding in the tissue induced by thermal, photothermal, and photochemical reactions-or a combination of all of these-is thought to be responsible for tissue welding. Laser tissue welding (LTW) has gained success in the laboratory using animal models. Transition from laboratory to clinical application requires the optimization of welding parameters. MATERIALS AND METHODS: A near-infrared (NIR) Cr(4+):YAG laser was used to weld ex vivo samples of human and porcine aorta and skin at wavelengths from 1430 to 1470 nm. Welding efficacy was monitored by measuring the tensile strength of the welded tissue and the extent of collateral tissue damage. Tensile strengths were measured using a digital force gauge. Changes in tissue morphology were evaluated using optical and scanning electron microscope (SEM). Fluorescence imaging of the welded areas was also used to evaluate molecular changes following tissue welding. RESULTS: Full-thickness tissue bonding was observed with porcine aorta samples. No collateral damage of the aorta samples was observed. Tissue denaturation was observed with human aorta, human skin, and porcine skin samples. The optimum tensile strength for porcine and human aorta was 1.33 +/- 0.15 and 1.13 +/- 0.27 kg/cm2, respectively, at 1460 nm, while that for porcine and human skin was 0.94 +/- 0.15 and 1.05 +/- 0.19 kg/cm2, respectively, achieved at 1455 nm. The weld strength as a function of wavelength demonstrated a correlation with the absorption spectrum of water. Fluorescence imaging of welded aorta and skin demonstrated no significant changes in collagen and elastin emission at the weld site. CONCLUSION: The observation that welding strength as a function of wavelength follows the absorption bands of water suggests that absorption of light by water plays a significant role in laser tissue welding.     

Mechanical and tribological performance of a hybrid MMC coating deposited on Al–17Si piston alloy by laser composite surfacing technique

Laser composite surfacing (LCS) is a photon driven manufacturing technology that can be utilized for depositing hybrid metal matrix composite coatings (HMMC) on softer Ti/Al/Mg alloys to enhance their tribo-mechanical properties. LCS offers the advantages of higher directionality, localized microstructural refinement and higher metallurgical bonding between coating and substrate. The current research presents the tribo-mechanical evaluation and characterization of solid lubricant based Ni–WC coatings deposited by LCS on Al–Si piston alloy by varying the concentration of graphite between 5-to-15-weight percentage. The tribological behavior of LCS samples was investigated using a ball-on-plate tribometer. Results indicate that the surface hardness, wear rate and friction coefficient of the Al–Si hypereutectic piston alloy were improved after LCS of graphite based HMMC coatings. The maximum surface hardness of 781H_v was acquired for the Ni–WC coating containing 5 wt% graphite. The friction coefficient of Al–Si under dry sliding conditions was reduced from 0.47 to 0.21. The reduction in the friction coefficient was attributed to the formation of a shearable transfer layer, which prevented delamination and reduced adhesion, abrasion and fatigue cracking.

The addition of graphite as solid lubricant has significantly reduced the friction coefficient and wear of a Ni–WC composite coating.     

口腔修复用钛锆铌锡合金机械性能及体内外的生物毒性

背景:在口腔修复领域广泛应用的纯钛和Ti-6AI-4V合金存在强度低,耐磨性较差,加工性能不理想,易出现卡环折断现象等缺点,并且含有人体有害的AI及V元素.因此,研制机械性能优良,生物学性能良好的口腔修复用钛合金,对于克服纯钛及钛合金修复体的缺陷,扩大口腔钛合金修复体临床应用范围,提高齿科修复体的质量及制作水平具有重要意义.目的:评价口腔修复用钛锆铌锡(Ti-12.5Zr-3Nb-2.5Sn)合金机械性能及体内外生物毒性.设计、时间及地点:对比观察实验,于2008-04/2009-02在天津市材料复合与功能化重点实验室、天津医科大学附属口腔医院口腔生物材料实验室及天津市现代医药开发研究所完成.材料:纯度为99.9%的钛板,纯度为99.9%的锆板,纯度为99.9%的铌棒和纯度为99.9%的颗粒状锡由宝鸡市胜超有色金属材料有限公司提供.方法:制备Tj-Zr-Nb-Sn合金,测试合金的机械性能和显微硬度,观察拉伸试样的金相组织、物相结构及断口形貌.参照ISO7406 技术报告中的相关标准,对Ti-Zr-Nb-Sn合金进行细胞毒性实验和急性全身毒性试验.主要观察指标:机械件能,合金金相结构,端口形貌,细胞相对增殖率,急性毒性反应.结果:Ti-12.5Zr-3Nb-2.5Sn 抗拉强度为(652.0±34.5)MPa,屈服强度为(590.0±29.8)MPa,延伸率为(28.3±2.4)%,弹性模量为(93.8±7.9)GPa,维氏硬度为(315.8±13.0)HV,XRD分析显示合金显微组织主要为α相,金相组织表现为细小的针状α相结构,合金断口呈韧窝状形貌,体现出良好的韧性断裂特征.细胞毒性试验及急性全身毒性试验结果表明本研究制备的钛锆铌锡合金细胞相对增殖度为124%,分级为0级,无细胞毒性;未见任何急性毒性反应.结论:Ti-12.5Zr-3Nb-2.5Sn 合金具有良好的机械性能和生物安全性,可满足口腔修复材料的临床应用要求.     

Multi-scale microstructure high-strength titanium alloy lattice structure manufactured via selective laser melting

The tensile performance of Ti6Al4V alloy lattice structure was investigated. Firstly, a face center cubic unit cell with vertical struts (F2CCZ) lattice structure was designed. Then, the structures were fabricated by selective laser melting (SLM) with different aspect ratios. Subsequently, the SLM-ed alloys were subjected to double solution-aging to homogenize the microstructure and release residual stress. It is shown that there is only acicular α′ martensite with high dislocation density in the SLM-ed alloy, while the heat-treated alloy has α and β phases (there are multi-scale α laths and nano-scale β particles), and the orientation relationship between the two phases is: [113]_β//[1210]_α. The tensile strength of the HT-ed alloys presents a significant increase from 140 ± 18 MPa in the SLM-ed state to 229 ± 5.1 MPa with an aspect ratio of 4. It indicates that the special heat treatment regime can not only homogenize the microstructure of the SLM-ed alloy, but also improve the tensile strength.

The tensile performance of Ti6Al4V alloy lattice structure was investigated.