钼铬等离子共渗形成表面低合金高速钢及其性能研究

在Q235钢表面进行等离子铬钼共渗，随后进行渗碳、深冷处理及低温回火处理，对其表面成分、硬度、摩擦因数进行了分析研究。结果表明：Q235钢表面成分接近冶金高速钢。合金层中的碳化物细小、均匀、弥散，没有粗大的共晶莱氏体组织。经深冷处理的试样表面硬度达到1600HV,明显高于未经过深冷处理的合金层表面硬度。经不同深冷处理试样的滑动摩擦因数基本相同，但与未经深冷处理的试样相比，摩擦因数降低大约15％。     

50钢表面强化及拉伸试验

在50钢表面进行等离子渗铬，形成表面高Cr合金层，再进行等离子超饱和渗碳、淬火及回火热处理，获得表面高性能强化层。对处理后的试样进行拉伸试验和断口形貌观察，结果表明：距表面的距离为0～0．1gm的渗层中Cr的质量分数为35％～38％；工作气体质量比Ar：CH4=1：1时，C的质量分数为1．42％，工作气体质量比Ar：CH4=1：1．2时，C的质量分数为2．26％；表面硬度达到HV1000左右；试样的抗拉强度随淬火温度的升高而降低，随碳的质量分数的增加而降低，抗拉强度最大提高近1倍；表面强化层的断口形貌均存在解理台阶，有少量韧窝存在，属于混合断口，而未经强化处理的试样存在大量韧窝，属于韧性断口。     

碳钢表面高铬耐磨合金层的制备及其组织与性能

采用双层辉光等离子渗金属技术先在Q235钢和45钢表面渗入元素铬,形成高铬合金层;然后进行等离子渗碳,得到高铬耐磨合金层;对渗铬、渗碳层的组织和性能进行研究。结果表明：表面层铬含量达到40％以上,且呈梯度分布;渗层所形成的含铬碳化物弥散、细小和均匀,表面含碳量达2．8％以上,没有共晶莱氏体组织;经淬火及回火处理后,表面硬度达到1800HV以上;与淬火GCr15钢相比,其耐磨性能提高7倍以上。     

H10Cr4Ni4Mo4V钢表面渗碳层硬度对接触疲劳寿命的影响

进行了H10Cr4Ni4Mo4V钢经渗碳热处理后，渗层表面硬度值的大小及均匀性对接触疲劳寿命的影响试验。结果表明，在渗碳表面硬度低或极其不均匀的情况下，其疲劳寿命远远低于渗层表面硬度高且均匀的试样寿命。在渗碳热处理时，渗层表面硬度值应控制在60．0～65．0HRC，且同一零件硬度差不大于2HRC。     

CVC8铝合金电子束改性的组织与性能的研究

利用电子束扫描处理对CVC8铝合金试样表面进行改性试验研究,以便提高铝合金表面的硬度和耐磨性。本文对铝合金电子束改性试样表层组织特征和金相结构进行分析,并对铝合金强化层的硬度和耐磨性进行了试验与测试。实验结果表明:铝合金电子束表面处理处理后,能够得到细晶粒的表面层组织,同时生成了非平衡态的共晶体和金属间化合物新相,改性层与基体材料间有过渡层组织,整个重熔区组织中无裂纹出现。铝合金电子束表面处理处理后表面硬度有所提高,是基体硬度的1.32倍。铝硅合金电子束表面处理层的表面的耐磨性相对基体有所提高,能够提高铝合金的耐磨性。     

碳氮共渗对马氏体钢轴承内圈接触疲劳寿命和失效机理的影响

对GCr15马氏体钢轴承内圈分别进行常规热处理和碳氮共渗+深冷+回火处理(简称碳氮共渗处理),通过对比研究了碳氮共渗对试验钢接触疲劳寿命及失效机理的影响。结果表明：碳氮共渗处理内圈试样中的碳化物比起常规热处理内圈试样更加均匀、弥散、细化,表面显微硬度和残余应力均显著提高;碳氮共渗处理内圈试样的额定寿命L₁₀,特征寿命L_63.2和中值寿命L₅₀分别约为常规热处理内圈试样的5.3倍,6.7倍和6.6倍;常规热处理和碳氮共渗处理内圈试样的接触疲劳失效损伤机理均为剥落,碳氮共渗处理后的亚表面裂纹萌生位置更深,亚表面二次裂纹的萌生与主裂纹的扩展得到抑制,抗接触疲劳性能得到提升。     

Q235钢表面低温气体N,C,O多元共渗的研究

利用自行研制的一种新型智能化低温气体多元共渗技术，在碳素结构钢Q235表面进行低温气体C，N，O多元共渗。经N，C，O多元共渗的Q235钢表面形成均匀渗层，渗层由钝化层、白亮层和过渡层组成，厚度约为100μm。Q235钢表面显微硬度显著提高，达到HV685。利用SEM对共渗层进行了成分分析，最外层钝化层中氧含量显著高于基体；渗层中白亮层氮元素的含量明显提高，在试样表面形成氮化物，从而大大提高了Q235钢的表面硬度；过渡层中碳元素的含量最高。     

热处理对渗铝45钢组织和性能的影响

借助金相显微镜、扫描电镜、能谱等对热处理后渗铝45钢组织和性能进行研究分析，发现表面渗铝退火处理后，渗层尺寸由263μm增加到364μm，渗层呈三部分，每层尺寸递减，扩散层I比较疏松，而与基体结合比较紧密的扩散层Ⅱ留于试样表面，退火前渗铝层硬度大于基体，退火后渗层硬度下降。     

预氮化对碳素工具钢560℃双辉等离子渗铬的影响

为了降低双辉等离子渗铬的工艺温度,提高低温渗铬速度,对T10钢表面在550℃进行不同时间的离子预氮化处理,再进行560℃×4h低温双辉等离子渗铬,对渗层的组织与硬度进行了研究.结果表明:各种条件下渗铬后,表面均形成铬的沉积层 扩散层,沉积层厚度4~5μm,组织致密,与基体结合良好;扩散层铬含量与显微硬度随预氮化时间的增加而增加,且均呈梯度分布;未经预氮化处理试样的扩散层深20μm左右,表面物相为铁、铁-铬固溶体、铬碳化物(Cr7C3,Cr23C6),表面显微硬度约700HV;预氮化后试样的扩散层深25~30μm,表面物相主要为铬、铁-铬固溶体、铬碳化物(Cr7C3,Cr23C6)、铬氮化物(CrN),显微硬度达915~1250HV,较未预氮化的试样提高45%以上.     

基于钴基合金覆层的多层金属热锻模原型制备与性能

基于功能梯度材料(FGM)的思想制备多层金属热锻模是提高模具寿命的有效方法。采用焊条电弧堆焊制备了多层金属热锻模的原型试样,试样经焊后热处理后,进行了金相组织分析、显微硬度测试、磨损实验和冲击韧性测试等实验。实验结果表明:钴基合金堆焊层与W6Mo5Cr4V2堆焊层界面冶金结合情况良好;截面显微硬度呈梯度分布,表面钴基合金硬度达到492HV;制备的多层金属试样耐磨性是H13钢耐磨性的2.5倍,冲击韧性处于合理范围。     

等离子表面渗铬渗碳耐磨合金层

利用铬是碳化物形成元素且与α-Fe无限互溶的条件,在廉价低碳钢或中碳钢表面进行等离子渗铬,形成表面高铬合金层,当表面含铬量达到40%以上并在一定范围内渗层成分呈平缓的梯度分布时,再进行等离子渗碳,形成高铬高碳合金层。合金层中的含铬碳化物在固体状态下形成,属于二次碳化物。由于渗碳温度低,合金层的含铬量高,所形成的铬碳化物弥散、细小、均匀,当表面含碳量达2.8%以上时没有共晶莱氏体碳化物组织,表面高铬高碳合金层经淬火及回火处理后表面硬度达到HV1800。磨损试验表明,与淬火GCr15材料相比其耐磨性能提高8倍以上。     

On the comparison of the abrasive wear behavior of aluminum alloyed and standard Hadfield steels

The abrasive wear behaviors of aluminum alloyed Hadfield steel at the high and low stress wear conditions were studied and compared with non-Al alloyed Hadfield steel. The wear tests were done with the pin on disc method using the abrasive wheel. The main parameters such as alloy compositions, normal load, sliding speed and sliding distance were evaluated. It is shown that at the low stress condition, the aluminum alloyed Hadfield steel has higher wear resistance than the non-Al alloyed Hadfield steel. But at the high stress wear conditions, the non-Al alloyed Hadfield steel is more resistant than the Al alloyed.     

Tribological Properties of Double-Glow Plasma Surface Niobizing on Low-Carbon Steel

The niobized layer was formed on Q235 low-carbon steel by double-glow plasma surface niobizing to improve its wear resistance. The microstructure, phase composition, and microhardness were determined. The friction and wear properties of the niobized samples and the untreated alloys were tested on a ball-on-disk tribometer by rubbing against GCr15 and silicon nitride (Si₃N₄) balls at room temperature and 400°C, respectively. The results indicated that the alloyed layer that contained a sediment layer and diffusion layer is about 35 μm in thickness, metallurgically adhered to the base metal. Niobium content was gradually decreased along the depth direction from the surface, which was similar to the change in the microhardness. The alloying layer mainly consisted of Nb, Fe₂Nb, and FeNb phases. Under unlubricated sliding conditions, the friction coefficients and the specific wear rates were lower than those of the untreated carbon steel at room and high temperatures. The wear mechanism of the niobized specimen at room temperature is dominated by slightly abrasive wear, whereas the predominant wear mechanism is abrasive wear and fatigue delamination at high temperature.     

Wear behaviour of some low alloyed steels under combined impact/abrasion contact conditions

The wear behaviour of some low alloyed steels has been investigated using a laboratory impeller–tumbler wear test equipment in which the steel samples are worn by angular granite particles under combined impact/abrasion wear contact conditions. The wear of the steels was evaluated by weight loss of the steel samples while the wear mechanisms of the steels were investigated by post-test light optical microscopy (LOM), scanning electron microscopy and energy dispersive X-ray analysis. The worn steel surfaces display a very rough surface topography with pronounced craters and distinct grooves caused by high and low angle impacts, i.e. abrasive wear, respectively. Besides, fragments of embedded granite particles are frequently observed in the worn surface of the steels. The wear of the steels tends to decrease with increasing steel hardness. However, instead of using the bulk hardness value the hardness of the worn/plastically deformed surface layer should be used when modelling the wear resistance. Further, the wear resistance of the steels was found to be dependent on the microstructure and chemical composition. Steels with similar type of microstructure show a linear decrease in weight loss with decreasing grain size and increasing carbon content.     

低碳钢表面氩弧硼-碳合金化工艺研究

以氩弧为热源,将含硼、碳的合金粉末熔入低碳钢表面使其合金化。这种方法能快速、便捷地对低碳钢表面进行强化。强化层厚度在2.5-4.0 mm。强化层与基体的结合为冶金结合。获得的强化层中主要强化相是Fe2B和Fe3(B,C)。强化层硬度可达62-67 HRC,并有良好的抗粘着磨损和抗磨料磨损能力。     

Microstructure and wear resistance of CP titanium laser alloyed with a mixture of reactive gases

Laser processing is a promising technique for alloying and synthesis of wear resistant layers. In this work, commercially pure titanium was laser alloyed with various proportions of nitrogen and carbon monoxide in order to produce a composite surface layer. The following gas mixtures were selected: 100% N₂, 67% N₂ + 33% CO, 50% N₂ + 50% CO, 33% N₂ + 67% CO and 100% CO. The microstructure, roughness and composition of coated specimens were characterized. The presence of Ti(C,N,O) in the surface layer was assessed by X-ray diffraction, X-ray photoelectron spectroscopy and Auger electron spectroscopy. The abrasive wear resistance of coatings was determined and related to their surface hardness. The abrasive wear resistance of the laser alloyed coating was substantially improved compared to untreated titanium and appears to be superior when composed of Ti(C,N,O) prepared from a mixture of gases.     

TURNING STUDIES OF DEEP CRYOGENIC TREATED P-40 TUNGSTEN CARBIDE CUTTING TOOL INSERTS – TECHNICAL COMMUNICATION

In the present work, coated tungsten carbide tool inserts of ISO P-40 grade were subjected to deep cryogenic treatment at ?176°C. Turning studies were conducted on AISI 1040 workpieces using both untreated and deep cryogenic treated tungsten carbide cutting tool inserts. The turning performance was evaluated in terms of flank wear of the cutting tool inserts, main cutting force and surface finish of the machined workpieces. The flank wear of deep cryogenic treated carbide tools was observed to be lower than that of untreated carbide tools in machining of AISI 1040 steel. The cutting force during machining of AISI 1040 steel was lower with the deep cryogenic treated carbide tools when compared with the untreated carbide tools. The surface finish produced on machined AISI 1040 steel workpieces was superior with the deep cryogenic treated carbide tools as compared to the untreated carbide tools.     

Influence of counterbody material on fretting wear behaviour of surface mechanical attrition treated Ti–6Al–4V

Surface mechanical attrition treatment (SMAT) was carried out on Ti–6Al–4V. Fretting wear tests were conducted using two counterbody materials (alumina and steel). SMAT resulted in surface nanocrystallization. Due to high hardness, low tangential force coefficient (TFC) and more TiO₂ layer, fretting wear resistance of SMAT treated samples was higher than that of the untreated samples. TFC values obtained with alumina counterbody were higher than those obtained with steel counterbody. The fretting wear resistance of untreated and treated samples fretted against alumina was lower than that of the samples fretted against steel due to tribochemical reactions at the contact zone.     

Abrasive wear resistance of some commercial abrasion resistant steels evaluated by laboratory test methods

The aim of the present study is to evaluate the abrasive wear resistance of some potential abrasion resistant steels exposed to different types of abrasive wear contact conditions typical of mining and transportation applications. The steels investigated, include a ferritic stainless steel, a medium alloyed ferritic carbon steel and a medium alloyed martensitic carbon steel.The abrasive wear resistance of the steels was evaluated using two different laboratory test methods, i.e. pin-on-disc testing and paddle wear testing that expose the materials to sliding abrasion and impact abrasion, respectively. All tests were performed under dry conditions in air at room temperature. In order to evaluate the tribological response of the different steels post-test characterization of the worn surfaces were performed using optical surface profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy. Besides, characterization of the wear induced sub-surface microstructure was performed using optical microscopy.The results show that depending on the abrasive conditions a combination of high hardness and toughness (fracture strain) is of importance in order to obtain a high wear resistance. In the pin-on-disc test (i.e. in sliding abrasion) these properties seem to be controlled by the as-rolled microstructure of the steels although a thin triboinduced sub-surface layer (5–10 μm in thickness) may influence the results. In contrast, in the paddle wear test (i.e. in impact abrasion), resulting in higher forces acting perpendicular to the surface by impacting stones, these properties are definitely controlled by the properties of the active sub-surface layer which also contains small imbedded stone fragments.     

GCr15钢等离子体源离子注入表面改性

用等离子体源离子注入技术对GCr15钢进行了氮离子注入,对注入层的成分进行了俄歇剖面分析,对注入层的显微硬度和摩擦性能进行了测试,对摩擦磨损表面进行了扫描电镜分析,研究结果表明;注入层的硬度和耐磨性均获得了明显的提高。