减轻渗硼层脆性的措施

综合分析了硼化物层的系列致脆因素,提出了若干减脆措施.添加镍、过渡族元素和稀土元素能够有效地降低渗硼层的本质脆性.依靠钢的精选、工艺材料的净化、多元渗硼及后续热处理工艺参数的优化等也可减小脆性.其中多元渗硼、激光重熔技术和自蔓延高温渗硼共晶化效果最为显著.     

9SiCr钢稀土硼钒共渗及其应用

研究了9SiCr钢稀土硼钒共渗层组织和性能及其在模具中的应用。实验结果表明，稀土的加入对硼钒共渗具有一定的催渗作用，使渗层增厚。稀土硼钒共渗可抑制FeB相的形成，共渗层Fe2B相呈细针状楔入基体，VC呈粒状弥散分布在Fe2B齿间和Fe2B与基体的过渡层中，组织均匀，致密，渗层耐磨性和耐蚀性粒稀土硼共渗有所提高，渗层脆性有所降低。采用该工艺处理的钢管挤压内模使用寿命较长。     

45钢膏剂渗硼而耐蚀性研究

通过试验探讨了４５钢渗硼后的组织和工艺参数对渗硼层厚度影响规律以及渗硼层的耐蚀性。结果表明：渗硼时间一定，渗硼层深度和渗硼温度呈负指数方关系；渗硼温度一定，渗硼层深度与渗硼时间呈抛物线关系；渗硼试样耐蚀性明显优于未渗硼试样，而单相渗硼层的耐蚀性又明显优于双相渗硼层。     

45钢膏剂渗硼及耐蚀性研究

通过试验探讨了45钢渗硼后的组织和工艺参数对渗硼层厚度影响规律以及渗硼层的耐蚀性。结果表明：渗硼时间一定，渗硼层深度和渗硼温度呈负指数方关系;渗硼温度一定，渗硼层深度与渗硼时间呈抛物线关系;渗硼试样耐蚀性明显优于未渗硼试样，而单相渗硼层的耐蚀性又明显优于双相渗硼层。     

退火与淬火工艺对45钢硼铬稀土共渗层组织性能的影响

介绍45钢渗硼工艺的实验方法,对渗硼层的显微组织进行了观察,分析了渗硼层的主要缺陷,从各种热处理工艺过程方面,探讨了影响渗硼层质量的主要因素。研究结果表明,渗层硼化物组织都呈梳齿状锲入基体,硼齿区最外层比次外层更疏松;过渡区有不同程度的增碳和晶粒粗大现象。     

钢的硼铝共渗工艺应用

对45钢电影机零件进行硼铝共渗，研究了硼铝共渗工艺，不同工艺参数对渗层厚度和组织结构的影响，结果表明，通过调整工艺参数，可以控制共渗层的组织结构，从而获得所需要的耐磨性、抗高温氧化性和低脆性。     

H13热作模具钢稀土硼碳氮多元共渗

对H13热作模具钢稀土硼碳氮共渗工艺进行了研究，并对其共渗层的组织、硬度及耐磨性和抗氧化性进行了测试与分析，结果表明与碳氮硼共渗工艺相比，稀土硼碳氮共渗层的硬度、耐磨性和抗氧化性明显提高。稀土元素的渗入不仅提高了渗层的硬度、耐磨性和抗氧化性，并且使过渡层的硬度变化减缓，增强了基体与共渗层的结合，为共渗层提供强有力的支撑作用。     

提高柴油机针阀偶件耐磨性的表面强化处理

本文着重于提高针阀偶件耐磨性的研究，对阀体进行高温渗硼处理，文中介绍了渗硼件的变形规律及控制方法，分析了渗硼层组织，找出控制脆性相Fe2B的方法，以获得高硬度的单相渗硼层，与之匹配的针阀进行物理气相沉积PVC处理，获得2500－2800HV的TiN层，针阀偶件高硬度的配合对提高耐磨性有重大意义。     

渗硼的渗层组织和性能研究

渗硼过程中,随着硼浓度的增加,渗硼层的组织由内向外依次为芯部基体、过渡层和硼化物层.如碳钢的低温硼氮共渗层呈梳齿状,表层由FeB、Fe2B双相组成,内层为Fe2B单相.合金钢低温硼氮共渗层的针状变得平坦,渗层的相组成较为复杂,Cr12钢低温硼氮共渗表层由Fe2B、FeB、Fe4N组成,内层相由FeB、Fe2B、Fe3 (C,B)、(Fe,Cr)2B、Fe4N、Fe3C等组成,过渡区形成Fe3 (C,B)、Fe4N相及Cr的碳化物,有效地强化了对硼化物层的支撑作用.渗硼层具有良好的耐磨性、耐腐蚀性.     

提高3Cr2MoWVNiRe钢热冲头寿命途径

本文研究了常规渗硼处理与硼氮复合渗不同处理对3Cr2MoWVNiRe电渣钢制热冲头寿命的影响。硼氮复合渗层既有渗硼层的高硬度、高红硬性、高耐磨性、比单渗硼低的脆性，又有良好的强硬化过渡层对渗层的支撑能力，充分发挥渗硼和渗氮各自优势，弥补各自不足，使用寿命比单一渗硼提高4－6倍，技术经济效益显著。     

RESEARCH AND APPLICATION OF AS-CAST WEAR RESISTANCE HIGH CHROMIUM CAST IRON

ＲＥＳＥＡＲＣＨＡＮＤＡＰＰＬＩＣＡＴＩＯＮＯＦＡＳＣＡＳＴＷＥＡＲＲＥＳＩＳＴＡＮＣＥＨＩＧＨＣＨＲＯＭＩＵＭＣＡＳＴＩＲＯＮＬｉｕＪｉｎｈａｉＬｉｕＧｅｎｓｈｅｎｇＬｉＧｕｏｌｕＨｅｂｅｉＵｎｉｖｅｒｓｉｔｙｏｆＴｅｃｈｎｏｌｏｇｙＷａｎｇＫｕ...     

Wear resistance of nanocrystalline composite NI-B coatings

The nanocrystalline composite electrochemical coatings prepared with nickel matrix and boron particles were investigated. Nickel plating bath of low nickel ion concentration (0.76 mol/dm³) with brightening organic compound, surfactants and dispersed boron particles content was used for coatings electrodeposition. Boron particles content was determined gravimetrically. The dependence of boron content in composite Ni-B coatings on the concentration and kind of the organic additives was investigated. The coatings structure was established using TEM. The microhardness of the deposited layers was measured by Vickers' method at the load of 0.01 and 0.05 kg. The wear experiments of Ni-B coatings were made without lubrication using the technique based on measuring system comprising a flat surface and a ball. On the basis of measurements of wear traces diameter, the wear depth was calculated and assumed as a measure of wear resistance. Tribological properties were investigated using the disc-block measuring system. Friction tests were made on Amsler A-135 machine.The obtained results suggest that the organic compounds used in the experiments had a significant effect on the increase of boron content in coating and the development of nanostructure of nickel matrix.     

1M2高速钢齿轮刀具激光熔凝强化组织与显微硬度研究

采用合理的工艺参数在原始组织为淬火态的M2（W6Mo5Cr4V2）高速钢齿轮刀具试样表面进行激光熔凝淬火,再在570℃温度下进行一次回火。根据显微组织的形态特征,划分出激光淬火加热层的分布区域;分析了显微组织与显微硬度的对应关系;建立了显微硬度拟合曲线的数学模型。研究表明,经激光熔凝淬火＋一次回火的M2高速钢加热层显微组织由外向内分为熔化区、微熔区、相变硬化区、回火软带和不充分回火区5个区域,并呈同心圆环分布,分别对应等轴晶及树枝晶、粗等轴晶及细等轴晶、马氏体＋残余奥氏体＋未熔碳化物、回火索氏体、短暂回火后略微软化的基体组织．与显微硬度具有良好对应关系;齿轮刀具激光熔凝淬火表面应该是后刀面和侧后刀面;高精度拟合的显微硬度曲线有助于预测和有效控制经激光强化的齿轮刀具刀刃精磨后在加热层中的位置及切削性能。     

Influence of Combined Addition of Boron and Strontium on High-Temperature Wear Behavior of A356 Alloy

In the present study, the effect of the combined addition of boron (B) and strontium (Sr) on the high-temperature dry sliding wear behavior of A356 alloy has been investigated using a pin-on-disc wear testing machine attached with a furnace. During wear studies, the effect of alloy composition, normal pressure, sliding speed, and sliding distance on A356 alloy at four temperatures, namely, room temperature and 100, 200, and 300°C, have been investigated. Further, the cast alloys and worn surfaces of A356 alloy with and without B and Sr were characterized by scanning electron microscopy (SEM)/energy-dispersive spectroscopy (EDS) microanalysis. Results indicate that the combined addition of B and Sr to A356 alloy has led to improvements in wear properties. This is due to a change in microstructure, improvement in mechanical properties, and the formation of an oxide layer between the mating surfaces during the sliding wear process.     

Surface Integrity and Machineability in Intermittent Hard Turning

Despite the large amount of research on hard turning, there are few results on intermittent hard turning. In this paper, the feasibility of internal intermittent hard turning has been investigated. First, the cutting tools with different cubic boron nitride (CBN) contents were evaluated, based on machineability: tool wear, surface roughness, and cutting forces. In the case of intermittent turning, low CBN content tools had better machineability than high CBN content tools. The depth of the machining damaged layer and the magnitude and distribution of residual stress were evaluated. The experimental results showed that intermittent hard turning can produce surface integrity which is good enough for replacing the grinding process.     

Contact and thermal analysis of transfer film covered real composite-steel surfaces in sliding contact

For composite-steel surfaces in sliding contact an anisotropic numerical contact algorithm has been developed to study the ‘layer type’ problems. An FE contact analysis was applied to evaluate the contact parameters (real contact area, contact pressure distribution and normal approach). The contact temperature rise was determined by using both a numerical thermal algorithm for stationary and a FE transient thermal technique for ‘fast sliding’ problems.The effect of a continuous transfer film layer (TFL), that had built up during wear of the PEEK matrix material on the steel counterpart, was considered. Its thickness was assumed to be t=1 μm, and its material properties were that of PEEK at room temperature or, in the case of frictional heating, at a temperature of 150°C (i.e. above the glass transition temperature of the polymer matrix).Results are presented for a spherical steel asperity, with/without TFL, sliding over composite surfaces of different fibre orientation, and in addition, for real composite-steel surfaces (based on measured surface roughness data) in sliding contact. The TFL has an effect on the contact parameters especially at higher operating temperatures (i.e. 150°C); it results in the production of a larger contact area and a lower contact pressure distribution. The contact temperature rise is clearly higher if a TFL is present. Due to the low thermal conductivity of PEEK, the TFL is close to the melting state or it even gets molten within a small vicinity of the contact area.     

Sliding Behavior of Some Layer Lattice Compounds in Ultrahigh Vacuum

Friction measurements have been made on a series of layer lattice compounds selected from a number of different crystal systems. Experiments in ultrahigh vacuum confirm the vapor lubrication mechanism for natural graphite, pyrolytic graphite, and boron nitride. For all other lamellar solids studied there was no evidence that vapor lubrication played a role in the sliding mechanism. It is likely that vapor lubrication applies to lamellar solids only when relatively high specific forces are acting between the layers.     

Contact Problems for Rolling with Slip for Viscoelastic Solids

The three-dimensional contact problem for rolling of a rigid sphere over a base, which consists of viscoelastic layer bonded to a rigid half-space has been considered. The thin viscoelastic layer simulates the action of a friction modifier. The Kelvin model has been used to describe the layer properties. The method of calculating the distribution of normal and shear stresses within the contact interaction area has been presented, the boundaries of traction have been determined, and the slip subareas have been studied. In addition, the influence of the viscoelastic layer properties on the distributions of contact stresses has been analyzed.     

Abrasive wear behaviour of hardened high strength boron steel

Abstract

Abrasive wear in industrial applications such as mining, materials handling and agricultural machinery constitutes a large part of the total wear. Hardened high strength boron steels are known for their good wear resistance and mechanical properties, but available results in the open literature are scarce. This work aims at investigating how different quenching techniques affect the two-body abrasive wear resistance of hardened high strength boron steels. Furthermore, the wear as a function of depth in thicker hardened high strength boron steel plates has also been studied. The material characterisation has been carried out using microhardness, SEM/energy dispersive spectroscopy and three-dimensional optical surface profilometry. The results have shown that water quenched and tool quenched high strength boron steel had similar wear resistance. The main wear mechanisms appear to be microcutting combined with microfatigue. Workhardening during the abrasion process has been found to affect the abrasive wear.     

Optimization of pulsed current in resistance spot welding of Zn-coated hot-stamped boron steels

Metallic coatings have been widely used for hot-stamped boron steel in automotive applications. Surface coating in hot-stamped boron steels has improved corrosion resistance. However, a thick coating layer degrades resistance spot weldability. In the case of a Zn-coated hot-stamped boron steel, the high contact resistance and material stiffness with low vaporization temperature of the alloyed layers result in a narrow current passage at the faying surface. Expulsion occurs at low current due to rapid heat development, resulting in a narrow weld current range. The pulsed current can control the heat input by applying a fast cool time during welding to improve the mechanical properties of the joint and acceptable current range. In this study, Zn-coated hot-stamped steels were resistance spot welded using various pulse current procedures, and welding condition was optimized via three pulsed current steps. Step 1: Contact area was controlled without nugget formation. Step 2: Nugget growth was minimized and contact area was maximized. Step 3: The maximum acceptable current range and nugget diameter were achieved. These welding conditions improved the acceptable current range and mechanical properties of spot welds due to increased spot weld size.