激光淬火齿轮组织和应力分析

采用扫描电镜、透射电镜和X射线应力分析系统，对齿轮宽带激光淬火后淬硬层显微组织和应力特性进行了研究，结果表明：激光淬火硬化区依其组织特征，大致分为3层：第1层为表面完全淬硬层，其主要是由马氏体和残余奥氏体组成；第2层为过渡层，由马氏体和基体上分布着回火析出的碳化物混合组成；第3层为高温回火区，由回火索氏体组织组成．激光淬火硬化层应力状态为压应力．     

齿轮宽带激光淬火组织和应力分析

利用扫描电镜、透射电镜和X射线应力分析系统,对齿轮宽带激光淬火后淬硬层显微组织和应力特性进行了细致分析.结果表明其组织分为:淬硬层、过渡层、高温回火区三层.淬硬层主要是由马氏体和残余奥氏体组成;过渡层为马氏体和回火索氏体混合组织;高温回火区由回火索氏体组织组成.激光淬火硬化层应力状态为压应力.     

T8A钢激光淬火工艺的研究

论述了不同原始状的T8A钢激光淬火后的组织和性能特征,并测定了淬硬层宽度、深度、残余奥氏体量及表面硬度等参数。实验结果表明:当功率密度一定时,改变扫描速度,T8A钢的淬硬层深度、宽度、残余奥氏体量及表面硬度均发生明显变化,当功率密度为2143W/cm~2,扫描速度为6mm/s时,最大淬硬层深度为0.77～0.83mm,表面层的组织为隐针马氏体、残余奥氏体和细小的碳化物,表面硬度达Hv790～1000。     

铸造C12A耐热钢焊接接头的金相组织分析

对铸造C12A高强耐热钢焊接接头的金相组织变化及硬度特点等方面进行了研究分析．试验结果表明：铸造C12A高强耐热钢经过焊接，基体组织没有明显发生变化，过热区的金相组织为板条马氏体 奥氏体组织，其硬度有所降低；熔化区的金相组织为针状马氏体 奥氏体 板条马氏体，硬度很高；焊后经过回火处理的基体金相组织与性能没有变化，过热区的金相组织为保留板条马氏体形态的回火索氏体组织，较基体组织要粗大，其硬度要比基体有所下降；熔化区的金相组织转变为保留板条马氏体的回火索氏体，但组织较为基体组织要细小，表现为硬度要比基体的有所升高．铸造C12A焊接后再经回火处理，可使焊接后的组织差别消除；性能变化趋于平缓，有利于材料的使用．     

激光淬火工艺参数对T10钢淬硬层深的影响

为探讨钢的激光淬火工艺参数对淬硬层深的影响。本文对T10钢进行了激光淬火试验。结果表明：淬硬层深随激光功率的增大、扫描速度的降低、激光束重叠尺寸的增大而增大,其中扫描速度对淬硬层深的影响相对较大;在功率（0．9－1）kW。扫描速度20－30mm/s,光斑直径3mm,激光束重叠1．0－1．5mm的工艺参数范围内,可获得不小于0．5mm的淬硬层深,表面硬度达HV1095左右;此外还发现,激光淬火前用碳黑进行黑化处理,有可能在T10钢表层形成亚共晶组织。     

中碳钢激光相变硬化组织中碳化物特性的研究

借助Ｈ－８００透射电子显微镜和Ｄ／ｍａｘ－ＲＣｘ射线衍射仪，对中碳钢激光淬火相变硬化区马氏体上弥散分布的碳化物进行了研究．试验结果表明，相变硬化区的组织为混合型马氏体且其上弥散分布着Ｍ３Ｃ型碳化物．此类碳化物对淬硬区硬度的提高起了非常重要的作用．     

液体软氮化高频淬火复合处理

一、前言近来,人们开始采用氮化加高频淬火工艺,就是将氮化处理生成的氮扩散层迅速加热奥氏体化,随后急冷,使其转变成含氮的细微马氏体。这种以提高机械性能为目的的复合热处理研究及其实际应用已引起了人们的注意。如象Levey等人,曾对气体氮化后的钢进行高频淬火来增加马氏体正方晶格的c/a比,使钢的疲劳强度及淬透性能都比单一淬州情况有一定程度的提高。高濑等人指出,经液体软氮化加高频淬火或渗碳淬火后,由于生成了Fe—C—N系的细微马氏体组织和加深了硬化层,故可提高机械性能。此外,大和     

氧乙炔火焰粉末喷焊及焊后热处理对基体,合金层组织结构与硬度的影响

本文采用光学显微镜、X射线衍射和硬度试验等方法,研究了氧乙炔火焰粉末喷焊及焊后热处理对40CrNiMo基体、合金层组织和硬度影响的规律。结果表明,火焰粉末喷焊使基体组织粗大,原淬火钢的回火索氏体,变成粗大的多相混合组织,硬度大大降低。喷焊后进行重新加热淬火,油冷到基体材料Ms点以下某一温度范围立即回火的热处理,使基体组织又得到了细化,硬度亦得到了恢复;而合金焊层没有受到影响,组织结构和硬度没改变。     

亚共析钢激光相变硬化显微组织的研究

研究了正火态基体和调质态基体的45钢激光淬火后的组织及其形成过程,指出由于激光相变硬化过程的高速性和极端的不平衡性,导至碳的局部区域扩散是造成正火态基体45钢激光淬火后,出现屈氏体多样化分层组织的根本原因。通过研究表明,45钢采用调质态基体进行激光淬火时,可使整个激光相变硬化层获得全马氏体组织。     

热处理工艺对40Cr组织和性能的影响

研究40Cr钢在不同热处理工艺下的组织和耐磨性.结果表明:40Cr最佳的热处理工艺为经850 ℃保温60 min正火,试样硬度约为200 HBS,正火后组织为索氏体;再经780 ℃淬火保温30 min后水冷,试样硬度约为52 HRC,淬火所得组织为板条状马氏体和针状马氏体;最后经200 ℃低温回火后,试样硬度维持在50 HRC以上,所得组织为回火马氏体;经淬火及回火后,试样耐磨性得到显著提高.     

铸铁激光表面改性的组织与性能特征的研究

论述了激光表面熔融处理后硬化层的显微组织与性能特征，讨论了组织对硬度分布的影响试验结果表明：经激光表面熔融处理后，球墨铸铁熔化层组织为先共晶奥氏体（快冷后转变为Ｍ＋ＡＲ）＋莱氏体，相变层组织为马氏体＋残余奥氏体＋球状石墨；灰口铸铁的熔化层组织为细小树枝（Ｍ＋ＡＲ）＋弥散分布的树枝间层片状变态莱氏体（Ｍ＋ＡＲ＋Ｆｅ３Ｃ）的变态亚共晶白口组织，相变层组织为马氏体＋残余奥氏体＋片状石墨在相变区，球状石墨周围的组织较复杂，靠近熔化层处的石墨球周围出现双壳层组织，由一层马氏体＋残余奥氏体包围，再围以莱氏体或先共晶奥氏体＋莱氏体组织     

Wear performance of laser surface hardened GCr15 steel

In order to assess the new tribological properties of laser surface hardened GCr15 steel, the wear resistance between specimens treated with laser and those of conventionally hardened under dry sliding conditions was compared. The change of wear mechanisms in laser hardened GCr15 resulted in a distinct difference in wear rates. The results showed that quenched zones not only had sufficient depth of hardening and higher hardness, but had more retained austenite and finer carbides because of a higher degree of carbide dissolution. Laser surface hardened GCr15 steel specimens exhibited superior wear resistance to their conventionally hardened specimens due to the effects of the microstructure hardening, high hardness and toughness. The wear mechanism for both the laser quenched layer and conventionally hardened layer was highly similar, generally involving adhesive, material transfer, wear-induced oxidation and plowing. When conventionally hardened block specimens rubbed against the laser hardened specimens, the surface of conventionally hardened block specimens was polished. The microstructural thermal stability was increased after laser surface treatment.     

Development of an ultrahard nanotwinned cBN micro tool for cutting hardened steel

Binderless nanotwinned cubic boron nitride (nt-cBN) synthesized from onion-structured BN precursors under high pressure and high temperature shows a very fine microstructure consisting of densely lamellar nanotwins (average thickness of 4 nm) within nanograins. The unique nanotwinned microstructure offers high hardness, wear resistance, fracture toughness, and thermal stability which are essential for advanced cBN tool materials. Thus, a circular micro tool of nt-cBN was fabricated using femtosecond laser contour machining followed by focused ion beam precision milling. Thereafter turning tests were performed on hardened steel using the studied micro tool. To evaluate the cutting performance, the machined surface quality and subsurface damage of the hardened steel were characterized. The wear mechanism of the nt-cBN micro tool was also investigated. It is found that the fabricated nt-cBN micro tool can generate high quality surface with surface roughness less than 7 nm and nanograin subsurface of about 500 nm deep. In addition, abrasive wear is found to be the dominant wear mechanism of the nt-cBN micro tool in turning hardened steel. These results indicate that nt-cBN has outstanding potential for ultra-precision cutting hardened steel.     

The Performance of SUF High Effective Concrete Crack-patching Material

The physical properties and microstructure of SUF are investigated to develop a highly effective cement matrix crack-patching material for concrete cracks. The SEM and XRD determination of hardened SUF shows that the microstructure of SUF is dense and compact with a lot of C-S-H gels and ettringite. Also , the mechanism of shrinkage compensating is discussed.     

工艺参数对45钢激光表面强化组织与性能的影响

通过改变激光功率和扫描速度等参数,研究其对45钢激光表面强化组织与性能的影响。实验结果表明,单道扫描时,当保持扫描速度v为15mm/s时,增加激光功率P,可增加硬化层的深度,最大深度可达1.5mm以上。另外,P/v比值越大,硬化层深度越大;而当P/v比值保持不变时,硬化层深度随着激光功率的增加而增加,其中激光功率从1.2kW到1.8kW时,硬化层深度值增加较快;当激光功率大于1.8kW后,深度值的增长随功率增加变缓;而且硬化层的硬度都达到700HV以上,远高于基体的硬度。在激光多道搭接扫描时,激光能量的再次输入会导致靠近搭接区的前一道硬化层产生回火软化,其硬度接近基体的硬度。     

Modification on the Performance of the Hemihydrate Gypsum with the Plant Source Polymer of Dry Matcha Powder

The objective of this study was to assess the feasibility of using the plant-source polymer of the matcha powder as a composite admixture for hemihydrate gypsum. Hemihydrate gypsum was mixed with different contents of matcha powder, and then the water requirement for the normal consistency, setting times, density, strength, hydration and microstructure of the hardened mixture were evaluated. The experimental results showed that it increased the water requirement for the normal consistency, and it regulated the setting times and reduced the density. Hemihydrate gypsum with more matcha powder had the higher water requirement, longer setting times and lower density. Less than 1% matcha powder had slight impact on the strength of hardened paste, but more than 1% matcha powder had a remarkable one. Matcha powder changed the hydration process and prolonged the induction and acceleration period. Small needlelike crystals were transformed into longer, larger and thicker ones as more matcha powder was mixed. This case is closely related to the prolongation of the induction and acceleration period. Besides, more and larger pores were observed in the hardened paste with more matcha powder. It is attributed to the appearances of the tea polyphenol in matcha powder and the larger and longer crystal morphology in hardened paste as well as the high water requirement for the normal consistency. These results are important to the application of matcha powder as a composite admixture for the hemihydrate gypsum as well as the prosperity and development of the tea industry.     

齿圈激光表面相变硬化处理技术研究

本文对齿圈齿面的激光表面强化技术进行了研究.提出了齿圈齿面激光表面淬火的偏置技术、变速扫描技术和辅助冷却技术,获得了沿齿面均匀分布的硬化层.检测表明:齿圈精度最大下降1级.采用扫描电镜和透射电镜,对齿圈激光淬火后淬硬层显微组织特性进行了分析,结果表明:激光淬火硬化区依其组织特征,大致分为三层.     

超快硬磷酸盐修补水泥水化硬化机理的研究

通过测定磷酸镁水泥的水化热和水泥净浆不同龄期的磷酸根离子浓度的变化，探讨了磷酸镁水泥水化硬化机理，并借助XRD、SEM等手段磷酸镁水泥硬化体的微观结构进行了分析。     

活性矿物掺合料对超高性能水泥基材料的影响

通过复掺粉煤灰和硅灰,制备一种抗压强度超过200 MPa的超高性能水泥基复合材料(UHPCC),采用扫描电镜、微区能谱分析、X射线衍射、汞压入法和差示扫描量热分析等现代测试手段,研究了活性矿物掺合料对UHPCC微观结构及性能的影响.实验结果表明,UHPCC水泥石主要以低mCa/mSi、结构致密的C-S-H凝胶和许多未水化颗粒组成;活性矿物掺合料的火山灰效应使水泥浆体与集料间界面过渡区得以改善;矿物掺合料的微集料效应使体系颗粒级配优化,致使基体内部结构致密,总孔隙率减小,孔尺寸得到细化,孔结构得以优化,材料性能得以提高.