粉末冶金Cu基金刚石工具的研究现状及进展

以金刚石颗粒为磨料,与金属胎体混合,经烧结制取的金刚石工具,为加工玻璃、花岗岩、大理石等硬脆材料不可替代的新型工具。本文阐述了Cu基金刚石工具的研究现状,主要包括Cu基胎体的分类、预合金化技术、金刚石表面金属化技术、稀土元素在Cu基金刚石工具中的应用等。研发新的合金体系与新技术,提高Cu基金刚石工具的综合性能,是今后的研究方向。     

稀土元素镧在金刚石工具胎体材料中的作用机理研究

研究了稀土元素镧对包镶金刚石颗粒的胎体机械性能、磨损性能及其对金刚石粘结性能的影响，确定了以ＬａＮｉ５合金粉末的形式添加稀土镧的方法，利用扫描电子显微镜分析了添加稀土镧前后胎体的组织结构变化、合金胎体中的元素分布情况以及胎体与金刚石之间的界面形态。     

变质系列锰钢耐磨性的研究

研究了变质系列锰钢的耐磨性与磨面硬度、磨面组织、主要磨损机制及磨损部击功之间的关系。结果表明，不同成分变质锰钢的耐磨性与磨损冲击功之间呈抛物线关系，耐磨性峰值的位置随锰含量的降低而向较低磨损冲击功方向移动；与耐磨性峰值对应存在着一个“最佳磨面硬度范围”和“适配冲击功范围”，在此范围内材料的耐磨性最高，主要磨损机制为显微切削＋浅小凿坑＋轻微剥落；钢中形成适量的形变诱发马氏体有利于耐磨性的提高。     

钎焊金刚石工具的研究现状与展望

从钎焊工艺、钎焊料、工具产品和生产自动化4个方面介绍了当前国内外钎焊金刚石工具的研究成果，并在此基础上对钎焊金刚石工具下一步的研究重点进行了展望。详细论述了钎焊温度、保温时间、钎料合金成分对钎焊金刚石的影响。适宜的钎焊温度和保温时间可以保证金刚石/钎料界面发生充分反应，界面结合强度增强，获得较好的钎焊接头质量。添加适量的元素或化合物改进钎料合金成分，可以调控钎料的性能，降低金刚石石墨化和热损伤程度。概括总结了常规钎焊金刚石工具、磨粒有序排布钎焊金刚石工具及细粒度钎焊金刚石工具的发展现状，钎焊金刚石工具具有电镀和烧结金刚石工具无可比拟的优点；金刚石有序排布会提高工具的加工效率和使用寿命，提高磨削表面质量；对细粒度钎焊金刚石工具亟待解决的磨粒等高性和分布均匀性问题的研究进行了概述。     

钛合金与钢的干滑动磨损行为对比

采用高温磨损试验机对TC11合金和H13钢进行了各种温度和载荷下的磨损试验,对比研究了它们的磨损行为。研究发现,随温度和载荷的变化,TC11合金和H13钢表现出完全不同的磨损行为。随着温度升高,TC11合金的磨损率在200℃时增加,然后大幅度降低,在400~600℃达到最低值。而H13钢的磨损率先降低,在200℃达到最低值,随后显著增加,在400~600℃出现从轻微至严重磨损的转变。其行为差异是由于氧化物的保护作用和两种材料热软化抗力的不同而引起的。     

GH4169镍基高温合金车削过程刀片磨损失效机理浅析

由于镍基高温合金在切削加工过程中易发生切削温度高、刀片磨损大、加工硬化现象严重等问题,导致镍基高温合金非常难以加工。本文通过对常规的车削过程的微观观测与分析,研究了镍基高温合金在车削过程中刀片的磨损失效过程与机理,以期为其切削性能的改善提供支持。结果表明,在切削GH4169镍基高温合金时,车削刀片的磨损形式主要包括前刀面磨损、后刀面磨损、沟槽磨损以及刀尖磨损。上述磨损形式由粘结磨损、磨粒磨损和氧化磨损几种磨损机理相互作用和影响形成。其中,粘结磨损是刀片切削镍基高温合金过程中最主要的失效机制,是引起其它失效形式的源头。     

开拓先进生产力 创造新成果

1金刚石表面金属化处理合金及工艺研究金刚石工具是以金刚石为磨料，以金属或树脂粉等为粘结剂制成的工具，它的工作能力（或使用寿命），不仅与金刚石的品质有关，而且与金刚石在粘结剂中的粘结状态和粘结强度有关。在以金属（或合金）粉末为粘结剂的金刚石工具中，由于金刚石与一般金属（或合金）之间的界面能很高，致使金刚石不能为一般金属（或合金）所浸润，从而造成金刚石在粘结剂中的粘结强度很小，致使金刚石过早脱落，其潜力得不到充分发挥。．湖南省冶金材料研究所完成的该项研究是一种在保护气氛下热扩散涂层（粉末状）技术。研…     

M50NiL轴承钢渗层碳化物特征与滑动磨损行为的研究

摘要：研究了M50NiL轴承钢在不同磨损时间和外加应力作用下的磨损行为和机制。结果表明：渗碳层组织为孪晶马氏体和近球状MC、M23C6和棒状M2C型碳化物。外加应力对钢的磨损形式与形貌具有显著影响，钢的磨损形式为轻微粘着磨损和磨料磨损，摩擦因数较快保持稳定到0.02。延长磨损时间对钢的磨损性能与机制具有明显作用，磨损时间达到3万s，MC、M23C6、M2C脱落，部分碳化物破碎形成磨料磨损。磨损时间与外加应力耦合作用显著影响钢的磨损性能与质量，磨损时间为3000s，外加应力由0306MPa增至1530MPa，碳化物导致磨料磨损，磨损质量由025mg增至038mg；外加应力增至2142MPa，更多大尺寸碳化物脱落，导致钢的摩擦因数逐渐升高至0037，磨损质量达到033mg。     

W对热压烧结铁基金刚石工具胎体组织性能的影响

采用机械合金化方法制备的铁基预合金粉作为主要结合剂,以金属w(W)0%~6%为添加剂,通过热压烧结方法制备金刚石工具胎体和金刚石/胎体材料,研究了W对胎体及金刚石/胎体复合材料密度、硬度、抗弯强度、把持能力和显微组织的影响。结果表明:W和金刚石的添加对热压烧结胎体及金刚石/胎体复合材料密度影响不大,随W的添加量增加,胎体硬度增加;W的添加,能够提高胎体对金刚石的把持能力,但随W含量的进一步增加胎体对金刚石把持力下降;W以颗粒形式弥散分布于Ni、Fe、Co骨架相附近或内部,少量分布于粘结相内部,使胎体显微组织细化和均匀化,胎体断口出现W颗粒脱嵌和穿晶解理。     

金刚石薄片

据美国的一份报告透露,纽约 Scomac Inc 公司的金属粘结金刚石工具专家 Leroy 提出一种制造金刚石工具的方法。这种工具,借用一台普通剪床,将嵌有金刚石磨粒的薄带切割成各种金刚石工具的形状,用焊接和钎焊将其固定在基体上而制成。与用磨料形成涂层的电铸法沉积金刚石工具情况相反,Scomac 材料通过将具有自由切割作用的金刚石磨料和铜或铝合金粉末混合,并将混合粉压制,最后在模具中烧结而成。这种长300毫米、宽75毫米的     

提高三角形金刚石多晶烧结体耐磨性的研究

采用粉末冶金方法进行人造金刚石多晶体的烧结。研究了提高多晶烧结体耐磨性的方法。通过工艺配方的确定、合成条件的选择、调整真空净化处理工艺以及使用高品质人造金刚石等措施，提高了多晶烧结体的耐磨性。     

THE TRIBOLOGICAL ASPECTS OF METAL-BONDED DIAMOND GRINDING WHEELS

Abstract

The field of metal-bonded diamond grinding wheels and saws is described. The production of these tools is an important part of the industrial-diamond industry, yet methods of construction, formulation and use raise practical problems that have not so far received a comprehensive and fundamental appraisal.

A theoretical approach to the subject is adopted in which the perfect wheel is considered in terms of a balanced system of matrix wear vs. the useful life of the diamond point. The discussion emphasizes the close association of grinding with tribology and explains how control of the wear of the metal matrix, together with the correct choice of diamond parameters, plays an important part in the performance of the wheel. It is stressed that lubrication during the grinding operation is the dominant factor in achieving maximum efficiency and economy.

The metal matrix is considered with regard to both its wear characteristics and its diamond-retention properties. Some wear data for common matrices are quoted, and reference is made to the use of fillers to modify matrix properties. The relation of theory to practice is then brought into sharper focus by reviewing methods of manufacture and the influences that lead to the choice of suitable production techniques.     

FeCoCrNiMo high-entropy alloys prepared by powder metallurgy processing for diamond tool applications

High-entropy alloys (HEAs) show good mechanical properties like high strength, hardness and wear resistance, and this makes them attractive for application in diamond tools. However, there are severe obstacles to improving the mechanical properties of normal diamond tools with metal-matrix alloys. Here, we report the formation of FeCoCrNiMo HEAs by powder metallurgy processing, starting from a gas-atomised powder followed by mechanical milling and consolidation by spark plasma sintering. Our results show that FeCoCrNiMo HEAs with pure FCC phase can be obtained by this method. Specimens with higher hardness can be obtained at higher temperatures and low pressures, while specimens with higher bending strength are formed at lower temperatures and pressures. FeCoCrNiMo HEAs have remarkably higher hardness and better wear behaviour than metal-matrices commonly in used diamond tools, which indicates that a new type of diamond tool with superior properties can be realised from HEAs.

Special theme block on high entropy alloys, guest edited by Paula Alvaredo Olmos, Universidad Carlos III de Madrid, Spain, and Sheng Guo, Chalmers University, Gothenburg, Sweden.     

石材切割锯片金刚石刀头磨损状况的研究

研究了花岗石锯切过程中金刚石锯片刀头的磨损状况,对刀头结合剂和金刚石磨粒的磨损机理进行了分析,并探讨了金刚石磨粒的磨损形态对金刚石锯片锯切性能的影响。     

Wear Resistance of Bronze-Matrix Samples of Diamond Tubular Drills with Ultrafine Diamond and Molybdenum Powder Reinforcement

The paper examines the abrasive wear rate of samples produced by vacuum impregnation of ultrafine diamond (ASM 1/0) and molybdenum powders with tin bronze. The tests were performed using a SiC-based abrasive wheel in the presence of cooling water. The introduction of and increase in the ultrafine diamond powder in the samples substantially decrease their wear rate (by a factor of 78). The hardness of the samples first increases when diamond powder content rises to 5 wt.% and then decreases when ASM 1/0 content further rises to 11 wt.% because of small porosity that appears in the samples. The use of a bronze matrix containing more than 15 wt.% Sn does not decrease the wear rate of the test samples and, hence, of the associated diamond tools, in spite of increase in their hardness.     

金属-金刚石的粘结界面与金刚石表面的金属化

研究了在铜基合金中添加强碳化物形成元素,在液相下通过与金刚石表面的界面反应而改变了金刚石与合金的界面形态,从而实现合金对金刚石的粘结。进一步提出了金刚石表面金属化的模型和技术途径。这种表面金属化的金刚石颗粒具有一般金属颗粒的可烧结性、可焊接性及表面可导电(可电镀)性。强化了粉末治金或电镀金属基体对金刚石颗粒的粘结力,可大幅度提高金刚石工具的水平。     

The transition from mild to severe wear in alumina during sliding

The occurrence of a wear transition in alumina during sliding has been investigated experimentally. The results show that a transition from initially mild wear to severe wear occurs abruptly, but only after a defined period of initial wear. The time required for this transition increases with decreasing grain size and decreasing applied load. Examination of wear samples revealed that, during the initial stage, surface material is removed by a plastic grooving process and is accompanied by the accumulation of subsurface dislocations arrays and twins. With continued sliding, internal stresses associated with this accumulating damage eventually results in grain boundary cracking and grain pull-out, which leads to the onset of fracture dominated, severe wear.     

WEAR OF ROCK-CUTTING TOOLS

Abstract

The conditions under which carbide-tipped rock-cutting tools are employed are very much more severe than any experienced under metal-cutting conditions, vibration of the cutting machine being very significant. Cutting rock also tends to be an intermittent process.

Once macroscopic chipping of the cutting edge has been overcome, the predominant mechanism of wear appears to be one of microfracturing of the surface layers, probably a high-strain-fatigue type of failure. For this reason pure WC–Co grades are usually employed for greater fracture-resistance, rather than other grades of cemented carbides. However, other mechanisms of wear are also probably operative, corresponding to abrasive mechanisms, and becoming more important as higher temperatures are generated. Recent hardness measurements indicate that at the temperatures generated in the carbide tip, especially when cutting quartzitic rock, grains of the rock material could well be harder than the tool material. At the wear flat, where a certain thickness of the rock has to be crushed, this can give deep scour marks.

The most significant improvements in the present range of WC–Co tools lie in the attainment of “extreme” freedom from porosity, and also in obtaining carbide grains that are structurally as perfect as possible. The latter condition is important, since it gives both a maximum resistance to fracture and also better retention of properties to higher temperatures. Other improvements are also largely directed at increasing the fracture-resistance of the carbides.     

金刚石工业用粉末材料的研究与发展

我国人造金刚石及其工具的发展,令世人瞩目。它的发展与粉末冶金息息相关。本文结合作者的研究工作,扼要阐述合成金刚石用的硬质合金顶锤、粉末触媒,制造金刚石工具用的金属胎体粉末在我国金刚石工业中使用现状及发展前景。     

Wear mechanism map of nitrided steel

Wear maps for untreated and gas nitrided BS970,905M39 (EN41B) steels have been constructed, which show the dominant wear mechanism regimes. The wear studies were carried out using a pin-on-disc machine under unlubricated conditions over a wide range of sliding speed and applied load, and the wear mechanisms were determined by examination of the worn specimens and wear debris. A sharp wear rate transition between mild (oxidative) and severe (metallic) regimes was identified for both untreated and gas nitrided steels. Gas nitriding expanded the mild wear region toward higher loads and sliding speeds.