Plasma-arc growth of refractory single crystals from SHS products and green mixtures: an autoreview

Overviewed are the author’s results on the plasma-arc growth of refractory single crystals from SHS products and green mixtures with special emphasis on stability of the growth process.      

铸铁激光重熔技术在泥浆泵叶轮表面强化中的应用

介绍了利用ＧＪ－Ⅱ型连续ＣＯ２激光器对６ＳＰＳ正反循环两用流泵叶轮进行重熔处理的工艺方法，分析了重熔处理后表层的组织性能以及相关工艺参数的和渗层深度经重熔处理后的叶轮的使用寿命提高３倍以上。     

Cr12激光表面熔凝处理的组织和性能研究

采用CO2 连续波工业激光器在Cr1 2钢表面进行了激光处理试验 ,利用光学显微镜、电子显微镜观察了激光熔凝处理后Cr1 2钢的组织 ,并比较了激光处理前后的耐磨性。结果表明 ,激光熔凝后获得超细化的枝晶组织 ,其组织为树枝状初晶A′和树枝间层片状共晶 (A′ +(Cr、Fe) 7C3 )。组织细化 ,奥氏体应力应变诱发马氏体转变 ,磨损中大量位错团的产生是激光处理后Cr1 2钢耐磨性提高的原因。     

轧辊制造技术与发展趋势

介绍了生产轧辊的四种常规方法以及随着轧制技术的发展而陆续发展起来几种生产轧辊的新方法,分析了每种方法的优缺点,并介绍了国内轧辊制造业现状及国际轧辊制造技术的发展趋势,对现实生产具有一定指导意义。     

高温合金表面包覆涂层的激光重熔研究

应用2kW-CO_2激光器,在 GH140合金表面进行 NiCoCrAlY 包覆涂层重熔处理。结果表明,控制恰当激光工艺参数,可使激光重熔区成分稀释度低,组织细化,涂层致密性、附着力显著提高。从而有效改善了抗蚀性和抗冷热疲劳性,并保持原涂层良好的塑性。     

电渣重熔钢锭内部中心孔洞的形成原理研究

针对电渣重熔钢锭出现内部孔洞废品的原因进行了研究分析，揭示了其形成原理，为实际生产中保障产品品质提供了有力帮助。     

高速钢激光重熔后的组织与性能

研究了W18Cr4V高速钢激光重熔后的组织与性能。结果表明，常规淬回火组织经激光重熔后其硬度、韧性都有提高，熔化层的残余应力为技应力；经640℃回火后；由于残余应力的消除及重熔组织中马氏体的二次硬化和残余奥氏体的二次淬火效应其耐磨性能有了进一步地提高。     

激光重熔工艺参数对热障涂层热震性能的影响

在GH536高温合金基材上等离子喷涂氧化钇部分稳定氧化锆(8YSZ)热障涂层后,采用连续CO2激光进行表面陶瓷层激光重熔,得到了表面形貌、组织结构符合质量要求的涂层。热震试验结果表明,在本试验的失效判据下,等离子喷涂及激光重熔试样的失效形式和机理不同,等离子喷涂试样为热震应力失效,激光重熔试样以热震应力和TGO应力共同作用形式失效。激光能量密度为4.0J/mm2时,激光重熔试样具有略高于等离子喷涂试样的热震寿命,当激光能量密度较高时,激光能量分布不均导致的组织及结构的不均匀,柱状晶粗化是能量密度较高的表征,扩展到喷涂态陶瓷层中的裂纹是激光重熔试样热震寿命降低的主要原因。     

激光重熔制备TA1表面Ni/Al复合抗高温氧化涂层

为了提高纯钛的高温抗氧化性能,采用电弧喷涂和等离子喷涂方法在纯钛表面制备Ni/Al复合涂层.利用激光重熔使得Ni层与Al层发生冶金反应,对试件进行800℃×40 h连续氧化.根据生成的金属间化合物特征研究纯钛的高温抗氧化行为.结果表明,经过表面改性处理后Ni/Al复合涂层可以显著提高纯钛的高温抗氧化性能.在激光重熔过程中Ni/Al复合涂层中的Al发生熔化扩散并与Ni形成以Ni_2Al_3相为主的扩散层.在氧化过程中Ni/Al复合涂层表面形成连续且致密的α-Al_2O_3氧化膜与大量NiAl相,表面扩散层中的富铝相可为表面提供充足的Al元素,进而对纯钛基体提供有效的高温抗氧化保护作用.     

Homogenization of Carbides in Ni60/WC Composite Coatings Made by Fiber Laser Remelting

In the current study, the effect of laser remelting on homogenization of carbides in WC-reinforced Ni60 composite coatings was investigated. Ni60 + 50 wt% WC composite coatings were fabricated on the surface of Q550 steel by LDF4000-100 fiber laser device. First cladding layer was made by rectangle laser spot and then circular laser spot was utilized to remelt the coatings. Microstructure characteristics were investigated by optical microscope and scanning electron microscopy. Elemental distribution and phase constitution were analyzed by energy disperse spectroscopy and X-ray diffraction. The results showed that accumulation of residual WC particles was sufficiently eliminated under the effect of laser remelting. The irregularly shaped carbides in first cladding layer were transformed into well-distributed polygonal carbides by laser remelting. Statistical analysis indicated median size of reinforcement particles decreased from 35.40 to 5.62 µm. Microhardness of remelted region had a smooth profile and decreased by ?50 HV_0.1 than that of first cladding region. Homogenization of carbides in nickel composite coating was well realized by laser remelting.