Effect of boron on the distribution and amounts of carbide phases in austenitic steel

Metal Science and Heat Treatment -     

热浸镀铝层中的非晶态金属相

采用SEM、TEM、XRD、EDS等手段研究热浸镀铝层的微观结构和成分。结果发现,镀铝层的表面层存在非晶态金属相。分别将热浸镀含稀土和不含稀土的铝液体急冷和缓冷后分析表明,镀铝后的铝-铁合金液在急冷过程中具有非晶形成能力;添加稀土后,非晶形成能力增加,即使在缓慢冷却条件下,组织中也有非晶态金属相形成。     

碳化钨/高锰钢堆焊层的制备工艺及耐磨性能

采用氧乙炔焰在Q235钢基体上制备碳化钨/高锰钢堆焊层,通过调节碳化钨的种类、粒度和含量来对比组织、性能上的差异。试验结果表明,在堆焊层中碳化钨颗粒分布均匀,颗粒周围产生共晶组织,且堆焊层的硬度随着碳化钨颗粒的数量、碳化钨颗粒尺寸的增加而上升;耐磨性随着碳化钨颗粒度的减小和碳化钨数量的增加而增加,其含量达到40%时为最佳,经冲击强化后堆焊层性能进一步提升。     

自生碳化物高锰钢堆焊层的组织与力学性能

利用药皮中钛铁、钒铁、石墨、稀土等的高温电弧冶金反应在金属堆焊层中自发生成碳化物增强颗粒,以提高堆焊层耐磨性.利用扫描电镜和能谱仪,对金属堆焊层中碳化物颗粒的形貌、分布及成分进行了观察和分析,测量了金属堆焊层的硬度并进行了耐磨性试验.结果表明,随着药皮中钛铁、钒铁的增加,堆焊层硬度提高,当加入12wt%钛铁、12wt%钒铁时,堆焊层硬度为65 HRC,耐磨性最好.     

Distribution of the carbide phase in the viscoplastic layer during the rotational friction-welding of various steels

The paper presents the viscoplastic phenomena observed during the rotational friction-welding process of high-speed steel M2 (AISI SAE) with carbon steel 1060 (AISI SAE). The structure, phase composition and distribution of the carbide phase in the friction plane and adjoining zones are examined by using optical microscopy (OM) with a system for quantitative analysis, and scanning electron microscopy (SEM) in addition to EDS analysis. The experimentally-checked mathematical relationship is suggested for the calculation of the radial movements of the carbide phase, immediately next to the friction plane. On the basis of qualitative and quantitative evaluation of the microstructural and rheological appearances, a model of carbide phase distribution is also established in the viscoplastic and viscous layers in the area of the friction plane.     

Effect of the size and distribution of excess carbides on the grain size of high-speed steel

Metal Science and Heat Treatment -     

Non-uniform distribution of rust layer around steel bar in concrete

The thickness of rusted layers at steel/concrete interface from a chloride-exposed reinforced concrete specimen was observed by digital microscopy. The non-uniform corrosion front is presented by a Gaussian function, the parameters in the model, including the non-uniformity coefficient, the spread coefficient, and the uniformity coefficient, are studied to describe the non-uniform distribute characters of rust layer. Comparing with the models proposed by other researchers, the Gaussian model can describe the non-uniform rust layer better. The location of corrosion peak along the perimeter of rebar and the condition for corrosion spreading across the entire circumference of rebar are discussed.     

The influence of secondary phase carbide particles on the passivity behaviour of NiTi shape memory alloys

The current investigation aims at studying the passivity behaviour of NiTi shape memory alloys with different levels of secondary phase titanium carbide (TiC) particles in an electrolyte of 0.9% sodium chloride at 37 °C. The influence of carbides and thermo‐mechanical treatment/cold working on the passivity breakdown is highlighted. The polarisation studies on the as‐cast and cold worked NiTi with high (0.05 wt%) and low (0.005 wt%) carbon levels show a significant difference in oxide stability. The alloy with extremely low carbon content shows a higher breakdown potential. Higher carbon levels result in higher density of larger TiC and these carbide/matrix interfaces are more susceptible to pitting. The qualitative behaviour of passive layer formed at 0.5 V on the cold worked NiTi alloy with different carbon levels was ascertained by electrochemical impedance spectroscopy (EIS). The oxide on the NiTi alloy with high (0.05 wt%) carbon levels showed lower resistance and poor stability at this condition.     

Microstructure and mechanical properties of WC-Co-based cemented carbide with bimodal WC grain size distribution

In order to improve the wear resistance of coarse-grained WC-Co cemented carbides,the fine WC powder were used to reinforce the metallic binder.These WC-Co-based cemented carbides having bimodal WC grain size distributions were synthesized by liquid phase sintering.For comparison,the cemented carbides having unimodal WC grain size distributions were synthesized.The microstructure,hardness,fracture toughness and wear resistance of these cemented carbides were investigated.The results show that ad...     

Effect of the size and shape of cementite particles on the structure and properties of deformed steel

Conclusions The shape of cementite particles has a considerable effect on the structure of deformed steel and its mechanical properties. The fine structure of ferrite resulting from plastic deformation of steel with globular cementite is similar to the structure of deformed carbon-free iron. Their dislocation structures are also similar. The shape, size, and internal structure of cementite crystals change little during plastic deformation (up to 50%). The strengthening of steel resulting from deformation is independent of the concentration of carbon and is the same as in carbon-free iron.Plate-like cementite, unlike globular cementite, favors the creation of a more dispersed ferrite substructure as the result of deformation. Also the cementite crystals become plastically deformed, and as a result a fine structure is created within the crystals. Most of the eutectoid grains are broken up during deformation, and as the result the plate-like structure is destroyed. In regions where the plate-like structure is preserved the cementite becomes finer and the distance between the platelets decreases. The finer the structure of the eutectoid before deformation the greater this effect. An increase of the dispersity of the eutectoid favors a more developed fine structure of ferrite and cementite as the result of deformation.Central Scientific Institute of Ferrous Metallurgy Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 2–8, February, 1964     

塑料模具钢表面激光熔覆WxC/Ni基合金涂层的组织及性能

采用TJ-HL-5000横流CO2连续激光器在2738塑料模具钢表面制备了WxC/Ni基合金涂层.利用金相显微镜、SEM、EDS、XRD、显微硬度计以及摩擦磨损试验机等检测设备研究了激光熔覆涂层组织及性能.XRD分析结果表明,熔覆层的主要物相有γ-Ni、W2C、WC、M23C6(M=Cr,Ni,Mo,W)、NiCr和Cr2O3等.金相显微镜、SEM和EDS分析结果表明,结合区为良好冶金结合,结合区为FeNiCrW合金,厚度为20 μm左右;基体对熔覆层合金的稀释度很低;熔覆层从界面向外依次分布着平面晶区、细等轴晶区、粗树枝晶区以及表面细晶区.显微硬度计结果表明,熔覆层的硬度值平均约900 HV1,是基体硬度的2.8倍左右.摩擦磨损试验结果表明,与基体相比熔覆层的耐磨性有了很大提高.