高碳高铬耐磨堆焊合金组织及性能

通过焊条电弧堆焊的方式形成高碳高铬(Fe-Cr-C)耐磨合金堆焊层,分析不同碳含量对堆焊层组织、硬质相及耐磨性能的影响。结果表明:堆焊金属的组织主要为M+A+C共+C初,初生碳化物类型为M7C3;随着碳含量的增加,初生碳化物的含量增加,且其生长方向趋于垂直于母材表面;堆焊层硬度随碳含量的增加而增加,但耐磨性在碳含量达一定程度(w(C)5.6%)时反而降低。     

改善GCr15轴承钢酸蚀低倍质量的生产实践

针对济源钢铁GCr15轴承钢棒材横截面酸蚀孔洞较严重的问题,分析酸蚀孔洞的成因.分析表明,贫铬区域抗酸蚀能力弱,优先形成孔洞,而成分偏析和网状碳化物的析出是造成铬元素分布不均的主要原因.为此,在实际生产中延长开坯加热时间和投用超快冷设备,最终酸蚀孔洞缺陷得到明显改善.     

过渡金属碳化物的催化研究进展

过渡金属碳化物作为一种催化新材料得到了人们广泛的关注,在催化加氢、脱氢、脱硫(HDS)、脱氮(HDN)和重整等方面,表现出优良的催化活性和选择性.综述了碳化钒、碳化钼、碳化钨、碳化铁、碳化钛等碳化物的催化性能和碳化物在各个反应中的催化机理的研究进展.     

Synthesis of Ternary Titanium Aluminum Carbides Using Self-Propagating High-Temperature Synthesis Technique

Different ternary carbide phases, namely Ti₃AlC₂, Ti₃AlC, and Ti₂AlC, were successfully synthesized in a self-sustaining regime. Direct reactions among elemental powders of titanium, aluminum, and carbon are strongly exothermic, and the resulting reaction products consist of binary carbides and they are partially molten. The use of TiAl, instead of elemental titanium and aluminum, significantly reduces the combustion temperature. As a result, ternary titanium aluminum carbide phases are formed. In addition, the combustion-synthesized products are not sintered and easy to deagglomerate. Reaction conditions and X-ray diffraction patterns of different ternary phases formed in a self-sustaining regime are presented.     

Elemental analysis of cemented carbides by calibration-free portable laser-induced breakdown spectroscopy

The process of cemented carbides manufacturing requires rapid and field elemental analytical techniques to control and evaluate the properties of products. Calibration-free laser-induced breakdown spectroscopy (CF-LIBS) is such a potential elemental analytical technique. In this work, a portable LIBS instrument combined with a CF method was developed for the analysis of cemented carbides. Three batches of cemented compact carbides without reference samples were analyzed. Qualitative and quantitative analysis of the samples were achieved by using the portable LIBS instrument combined with CF method. To validate the analysis results, X-ray fluorescence spectrometry (XRF) was used to analyze the samples as well. The results of CF-LIBS agreed well with the results of XRF, with relative errors between ?29.53 and 24.70%. The results demonstrated that the portable LIBS instrument combined with CF method was capable for direct and rapid analysis without any need of standard measurements. Notably, with the portable LIBS instrument combined with CF method, acceptable accuracy could be obtained, which is promising for practical field applications.     

Strengthening mechanisms of a new 700 MPa hot rolled Ti-microalloyed steel produced by compact strip production

A new hot rolled titanium-microalloyed steel with yield strength of 700 MPa has been developed by CSP (compact strip production) process based on commercial weather resistant steel. EBSD results showed that the average size of its grains with high angle boundaries (>15°) was 3.3 μm. High-density dislocations and large number of nanometer particles were observed in the steel product by TEM. X-ray analysis on the electrolytically extracted phase from the steel indicated that fraction of MX phase was 0.0793 wt%, in which the particles smaller than 10 nm accounted for 33.7%. The contribution of precipitation hardening resulting from nanometer particles was calculated as approximate 158 MPa. The commercial weather resistant steel, reference steel for comparison with 450 MPa yield strength, was also prepared and investigated. It can be concluded that grain refinement is still a major strengthening mechanism in this high strength steel, but precipitation hardening of nanometer TiC precipitates is the dominant factor to increasing the yield strength in new developed steel compared with the reference steel.     

低碳Ni-Cr-Mo铜中M/A岛及回火特性

采用现代高分辨电子－光学分析技术及光学显微镜等，对低碳Ｎｉ－Ｃｒ－Ｍｏ钢（Ｃ≥０．０６％）中Ｍ／Ａ岛及其回火特性进行分析。结果表明，有两种类型的Ｍ／Ａ岛，一种为可聚成团状的小尺寸Ｍ／Ａ岛（即粒状贝氏体中的Ｍ／Ａ岛），它所在的铁素体基体呈胞状结构，位错密度较高，胞状之间为小角度关系；另一种为孤立的块状Ｍ／Ａ岛（类似双相钢中的Ｍ／Ａ岛），它所在的铁素体基体与多边形铁素体类似，位锗密度较低，透射电镜下没有看到亚结构。前者Ｍ／Ａ岛碳含量较高，回火后析出的碳化物尺寸较粗大。而且前者Ｍ／Ａ岛中残留奥氏体量比后者高，故粒状贝氏体回火抗力较大是由于残留奥氏体量较多的缘故。     

热变形白口铸铁颗粒状碳化物的形成

探讨了热变形白口铸铁中颗粒状碳化物的形成，结果表明：尺寸较大的碳化物来源于铸态中棒状碳化物；尺寸较小的碳化物直接从基体中形核；尺寸介于两者之间的碳化物来自热变形诱发析出，且变形量越大则细小的颗粒状碳化物数量越多。     

Increasing the wear resistance of stainless steels

The wear resistance of martensitic, austenitic and duplex stainless steels is increased by carbon and nitrogen in solid solution and in addition by carbides and nitrides, which are formed during conventional ingot metallurgy or by powder metallurgical processing. High temperature and low temperature nitriding provide a hard surface zone. Characteristic alloys and applications are discussed, which try to optimize the resistance to wear and corrosion.