硬质合金基体对涂层刀具高速切削镍基高温合金切削性能的影响

采用热常数仪和高温维氏硬度计对Co含量(质量分数)分别为6%和10%的硬质合金进行热学性能与高温力学性能检测,然后用以这2种硬质合金为基体的涂层刀片对镍基高温合金GH4133进行高速车削,采用扫描电镜(SEM)和能谱(EDS)对车削后刀片的磨损区域进行观察和成分分析,研究刀片基体的Co含量对刀具切削性能的影响。研究结果表明,硬质合金中的Co含量由10%降低到6%时,热导率由62.78(W.m)/K升高到84.57(W.m)/K,与此同时同一温度下的高温维氏硬度提高10%左右;YBG202刀片(基体中Co含量为10%)的切削刃与后刀面的磨损均较迅速,而YBG102(基体中的Co含量为6%)刀片后刀面的磨损相对均匀,磨损速率低;基体中的Co含量由10%降低到6%时,刀片的切削寿命提高约3倍。故高速连续切削镍基高温合金时应当尽量选用低Co硬质合金作为刀片的基体。     

工艺参数对非平衡磁控溅射Ti/TiN/Ti(C,N)薄膜硬度的影响

 采用中频非平衡磁控溅射工艺，在316L不锈钢、高速钢和硬质合金3种基体材料上制备Ti/TiN/Ti(C,N)膜系的硬质薄膜。通过改变工作气氛、基体负偏压等工艺参数，对制备薄膜的硬度进行检测分析，结果表明：在Ti(C,N)薄膜的制备中，工作气氛和基体负偏压是影响薄膜硬度的主要因素。当工作气体的通入比例C2H2/(N2+Ar)＜1/9时，薄膜硬度较高。当通入的乙炔(C2H2)流量增加时，会明显降低薄膜硬度。当基体负偏压在一定范围内增加时，薄膜硬度随之逐渐提高；当负偏压增加到200 V时，薄膜硬度最大；负偏压超过200 V，薄膜硬度明显下降。基体材料对薄膜硬度的影响较大，在不同基体材料上镀制同一种硬质薄膜时，薄膜硬度不同；3种基体材料上沉积薄膜的硬度数316L不锈钢基体上的薄膜硬度最低。     

The influence of austenite grain size and its distribution on chip deformation and tool life during machining of AISI 304L

In this article, the influence of austenite grain size and its distribution on chip deformation and tool life during machining of AISI 304L austenitic stainless steel bar is examined. Hot-forged bar and the quenched bars (at different quenching temperatures, 1050 °C, 1100 °C, 1150 °C, and 1200 °C) are machined at a high cutting speed. It was noted that the inhomogeneous distribution of grain size in the surface area, within a depth of 15 mm of the workpiece, resulted in tool edge breakage and lower tool life when machining the hot-forged bar compared with all of the quenched bars. In addition, a slight decrease in tool life was observed as the grain size increased in the quenched bars. The chip studies revealed that a higher segment height ratio of chip was gained when machining the hot-forged bar, compared to machining the quenched bars, due to the inhomogeneous distribution of grain size. Moreover, the thickness of the secondary shear zone was reduced as the grain size increased. Interestingly, it was noticed that the chip work hardened during the machining process due to strain-induced twinning and ɛ martensite transformation. The studies of tool wear and failure revealed that a crack was initiated on the flank face at the interface between the deposited workpiece and the tool substrate when machining the hot-forged bar. This crack was formed due to either the thermal and mechanical fatigue or plastic deformation of the tool substrate. The fatigue crack propagated into the tool substrate through the decohesion of interface between carbides. The criterion of tool life when machining all of the quenched bars was normal flank wear. Based on the studies of chip deformation and the mechanisms for tool wear and failure, the effects of austenite grain size and its distribution on tool life were explained.     

高速切削铝合金用硬质合金刀具磨损机理研究

在高速切削加工铝合金涡轮过程中,硬质合金刀具的磨损会直接影响刀具的使用寿命和加工精度,导致加工精度无法满足设计要求,在磨损严重时还会引起刀具和零件的损伤。本文以高效切削铝合金涡轮用硬质合金刀具为研究对象,通过四因素三水平正交试验对刀具磨损行为进行研究,观测和分析不同切削参数下硬质合金刀具的磨损状态及微观形貌,讨论并提出有效控制刀具磨损的措施。结果表明,该控制刀具磨损的措施在保证零件加工精度的同时具有一定的实际推广价值。     

Rare earth ceramic cutting tool and its cutting behavior when machining hardened steel and cast iron

The addition of rare earth element yttrium played an important role in the improvement of both mechanical properties and wear resistance of Al2O3/(W,Ti)C ceramic cutting tool material.Mechanical properties especially the fracture toughness and flexural strength were obviously increased when a suitable amount of the yttrium were added.Wear resistance of the developed rare earth ceramic cutting tool material was higher than that of the corresponding materials without rare earth in the machining of the hardened 45# carbon steel and cast iron HT20-40.Wear modes of the Al2O3/(W,Ti)C rare earth ceramic tool materials were mainly flank wear and crater wear accompanied with slight notch wear when machining the hardened carbon steel.Wear mechanisms were major abrasive wear at low cutting speed and adhesive wear at high cutting speed.Wear modes were nearly the same except that the adhesion phenomenon in the crater area was intensified when machining cast iron.The flank wear area was relatively smooth with no obvious plowing phenomenon which was possibly concerned with the workpiece of low hardness and the adhesion phenomenon at high cutting temperature.     

Application of Thermodynamic Model for Inclusion Control in Steelmaking to Improve the Machinability of Low Carbon Free Cutting Steels

Oxide inclusions formed during steelmaking processes influence the machinability of steel products. At moderate and high cutting speeds, the tool life is dominated by chemical wear. However this wear can be suppressed by engineering exogenous and indigenous glassy oxide inclusions in steel. The present work demonstrates a method to engineer glassy oxide inclusions in a low carbon free cutting steel applying a new thermodynamic model for deoxidation control of steel based on slag‐melt as well as melt‐oxide inclusion equilibration. The model is used online in an industrial production line for the controlled production of glassy inclusions. These inclusions are shown to improve machinability by lubricating the tool‐chip interface during machining of the steel at high cutting speeds. Using an inclusion engineered work piece, the crater wear of an uncoated P10 tool is significantly improved and the tool life is tripled at cutting speeds in the range between 200 and 400 m/min. The industrial results show that thermodynamic modelling is a powerful tool to produce free cutting steels with consistently good machinability behaviour.     

Heat treatment in a protective atmosphere as a means of increasing the wear resistance of hard-metal tools

Conclusions An x-ray structural study has shown that heat treatment in a protective atmosphere with slow heating and cooling lowers the level of thermal microstresses in the WC phase of a hard metal. After the removal of the cobalt phase, the thermal microstress in the WC phase of a titanium-tungsten alloy falls by 25–35%. The cobalt phase has a strong compressing action on the tungsten carbide. Microstress variations affect the physicomechanical properties of a hard metal. In the lathe-turning of type 45 steel with titanium nitride-coated hardmetal tool tips (in the machining speed range v = 50–300 m/min) tool life is up to 70% longer than that attainable with uncoated tools. With increasing tool flank wear, the beneficial effect of the coating diminishes.Translated from Poroshkovaya Metallurgiya, No. 1(217), pp. 19–23, January, 1981.     

热像仪法实测陶瓷刀具切削区的温度场分布

采用ＴＶＳ－２２００型红外热像仪分别测定了Ｓｉ３Ｎ４、Ｔｉ（ＣＮ）陶瓷刀具以不同切削速度切削１０４５钢和１Ｃｒ１８Ｎｉ９Ｔｉ奥氏体不锈钢时前后面切削区温度场的分布。红外热像照片直观地呈现了陶瓷刀具切削区的辐射温度。通过计算机数据处理，获得不同陶瓷刀具在不同切削速度下切削不同材料时前后刀面的真实温度分布。成功地试验了一种新的陶瓷刀具测温技术，同时为研究陶瓷刀具磨损规律及机理，提高刀具寿命提供了科学依     

Alternatives to Lead as a Machinability Enhancer in Free Cutting Steels

Low levels of lead are added to free cutting steels to improve machinability. For environmental reasons, there is interest in alternatives to lead that are technically and commercially viable. The machining performance of eight low carbon free cutting steels with alternative machinability enhancers, including additions of bismuth, increased sulphur (with and without tellurium), tin and phosphorus, has been investigated. In tests with high speed steel tools and lubricant, the leaded steel showed the best performance in terms of production rate, surface finish and chip form. In tests with coated carbide tools at a range of cutting speeds the standard non‐leaded 11 SMn30 steel performed well in terms of tool wear, but showed poorer chip form than the leaded steel. The steels with increased sulphur showed improved performance compared with the 11SMn30 steel in tests using high speed steel tools and lubricant, but did not approach the leaded steel in terms of production rate. The steels containing tin did not generally perform better than the 11 SMn30 steel. The 11 SMn30Bi steel gave performance approaching that of the leaded steel in tests with high speed steel tools and lubricant. However, the cost of this addition may make it uneconomic for large scale use.     

Properties of a Tool Produced by Powder Metallurgy

To minimize the manufacturing costs of parts with specified operational properties, the machining processes must be optimized. Cutting accounts for at least 70% of such processes. To that end, tool materials with distinctive properties may be developed and utilized. Analysis of manufacturing components—in particular, power components in gas-turbine engines—shows the need for higher quality of the machined surfaces and more efficient use of expensive equipment with numerical and adaptive control systems, so as to ensure a wide range of cutting conditions, including high-speed cutting. To obtain products that are domestically and internationally competitive, we need to optimize cutting processes, in which the tool is the weakest link in the technological chain. Defects of the cutting tool impair the productivity and product quality. In the present work, the wear of cutting tools produced by the sintering of high-speed steel powder is studied. Tool materials based on high-speed steel with additional alloying by titanium carbide (carbide steel) are shown to be highly wear-resistant. They may be classified as a new category of self-organizing tool materials. The results indicate the expediency of additional alloying by two methods to modify the tool friction and wear: (1) alloying with compounds that considerably reduce the self-organization by decreasing the frictional coefficient at working temperatures; (2) alloying to expand the range of self-organization. Both methods result in lower frictional forces and temperatures, as confirmed by the change in wear resistance and frictional characteristics. The wear resistance of such tools is found to be 2–3.5 times that of regular high-speed steel tools.     

硬质合金涂层刀具研究的新进展

随着现代机械加工工业朝着高精度、高速切削、干式切削技术以及降低成本等方向发展,人们对硬质合金刀具提出了更高的要求。涂层硬质合金具有高硬度和优良的耐磨性,延长了刀具的寿命,这是切削刀具发展的又一次革命。本文综述了目前国内外硬质合金涂层刀具在涂层方法、涂层种类和涂层基体等方面的新进展。     

含硫齿轮钢20CrMnTiH中硫化物对切削性能的影响

在不同切削速度(200～230 m/min)和切削深度(0.5～2 mm)下试验研究了普通20CrMnTiH齿轮钢(0.006%S)和含硫20CrMnTiH齿轮钢(0.031%S)的切削性能。结果表明,随切削速度增大,刀具的磨损增大,在200 m/min,0.031%S钢是0.006%S钢刀具的使用寿命的2.8倍;在230 m/min,0.031%S钢是0.006%S钢刀具使用寿命的2.6倍;随切削深度增加,切削力增加,但在相同切削深度下,0.031%S钢的切削力低于普通0.006%S钢;由于0.031%S钢存在≤6μm的MnS夹杂,使切屑易断,并硫化物夹杂能够包裹Al₂O₃尖晶石夹杂,减少刀具磨损,提高钢材的切削性能。     

Grain size of high-speed tool steels

Influence of the carbide population on austenite formation during hardening of high speed tool steels has been investigated. It was established that austenite grain size varies directly with the mean primary carbide size or interparticle spacing. The type of annealing treatment—temper annealing or transformation annealing—given prior to hardening has an additional effect on the subsequent austenite grain size. This effect is related to the characteristics of the secondary carbide population. Austenite grain refinement was found to significantly improve the performance of high speed steel tools operating under intermittent cutting conditions. The observed tool wear during intermittent cutting is explained in terms of a combination of mild wear and “microspalling” mechanism at the cutting edge.     

Microstructure and its effect on toughness and wear resistance of laser surface melted and post heat treated high speed steel

High speed steel hacksaw blade blanks were laser surface melted and rapidly solidified along one edge. The laser melting resulted in complete carbide dissolution. By subsequent machining and heat treatments saw teeth were manufactured with a refined internal structure of the edges and corners. The structure was fully martensitic with a uniform and dense dispersion of small primary carbides. Sawing tests in quenched and tempered steel showed that blade life was somewhat improved, as compared to conventionally heat treated blades. The increased wear resistance is believed to be due to improved toughness along with high hardness caused by the refined carbide structure. Sawing tests in austenitic stainless steel did not give any significant improvement in performance. The effect of the altered microstructure on performance is likely to be more or less pronounced depending on application, tool and work material.     

Development of Cutting Tool Through Superplastic Boronizing of Duplex Stainless Steel

In this study, a cutting tool is developed from duplex stainless steel (DSS) using the superplastic boronizing technique. The feasibility of the development process is studied, and the cutting performances of the cutting tool are evaluated and compared with commercially available carbide and high-speed steel (HSS) tools. The superplastically boronized (SPB) cutting tool yielded a dense boronized layer of 50.5 µm with a surface hardness of 3956 HV. A coefficient of friction value of 0.62 is obtained, which is lower than 1.02 and 0.8 of the carbide and HSS tools. When tested on an aluminum 6061 surface under dry condition, the SPB cutting tool is also able to produce turning finishing below 0.4 µm, beyond the travel distance of 3000 m, which is comparable to the carbide tool, but produces much better results than HSS tool. Through superplastic boronizing of DSS, it is possible to produce a high-quality metal-based cutting tool that is comparable to the conventional carbide tool.     

新一代自润滑无铅易切削钢的开发

 应用炼钢过程中夹杂物控制的热力学模型预测钢包精炼和钢液凝固后钢中氧化物夹杂的成分,在模型预测指导下进行了自润滑易切削钢工业生产试验,并对开发的易切削钢进行了切削性能测试。结果表明,钢中氧化物夹杂预测结果与实测结果一致;用无涂层P10刀具进行的切削试验结果也表明,与传统含铅易切削钢相比,自润滑易切削钢在高速(v≥200 m/min)切削条件下,后刀面磨损降低200%;切削速度v=100 m/min时,二者相当;v=200 m/min时,前刀面月牙洼磨损降低200%,且月牙洼离刀刃较远。说明在高速切削条件下,开发的新一代自润滑易切削钢的切削性能明显优于传统含铅易切削钢,完全可替代传统含铅易切削钢。     

Effect of Additive Cu-10Sn on Sintering Behavior and Wear Resistance of 316L Stainless Steel

 Austenitic 316L stainless steel has good corrosion resistance; however, the relative softness often limits its application. Severe adhesive wear often occurs between the 316L stainless steel and the metal counterpart. Cu-10Sn alloy is often used to improve the wear resistance of powder metallurgy 316L stainless steel. The influence of Cu-10Sn on sintering behavior and wear resistance of powder metallurgy 316L stainless steel was investigated. The parameters investigated included sintering temperature and volume percent of Cu-10Sn. A maximum relative density of 97% was achieved with 25% (in volume percent) Cu-10Sn content at a sintering temperature of 1300 ℃ for 60 min. The irregular and sharp angles of 316L stainless steel particles become round, and the pores are removed completely as a result of large amount of liquid phase formed during sintering. The minimum friction mass loss was achieved with 25% Cu-10Sn content.     

Some features of cutting tool wear in finish machining of low-porosity alloy powder metallurgy steels

Conclusions The presence in powder metallurgy steels being machined of voids even in an insignificant quantity has a significant influence on the amount and character of wear of the cutting tool. Even a decrease in residual porosity to 0.5% provides a significant increase in cutter life.In connection with the fact that the character of wear of sintered carbide cutters in machining of low alloy powder metallurgy is primarily adhesive, VK8 cutters, which have higher cyclic impact strengths, have the best life.As tool materials in machining of powder metallurgy steels at cutting speeds of more than 200 m/min it is desirable to use mineral ceramic materials.Translated from Poroshkovaya Metallurgiya, No. 2(254), pp. 74–79, February, 1984.     

Wear Mechanism and Cutting Performance of Conventional and High-Strength PM High-Speed Steels

Abstract

One of the reasons for employing PM techniques in the manufacture of high-speed steels is to avoid the carbide clusters that limit the strength of ordinary high-speed steels. The combination of proper PM techniques, upgrading the steel to an optimum chemical composition, and correct heat treatment results in superior strength and toughness characteristics. The effects of a superior cutting edge strength on the tool wear and the tool performance of some broaches and milling tools are discussed. The life of broaches may be greatly improved while, in the case of milling tools, the machining rate may also be raised. Case studies from actual production are used as illustrations. For high-quality industrial tools, the best way of saving scarce and expensive alloy metals may not be to lower the alloy content of the tool, but to make sure that the tool is capable of machining more components. The crucial factor is the alloy expenditure per machined component. PM/0189     

THE WEAR RATE OF CARBIDE CUTTING TOOLS

Abstract

The stress, strain, and temperature at the interface between tool and work material during metal cutting are such as to promote seizure. Conditions of seizure normally exist over part of the interface during most metal-cutting operations. The wear processes that are significant on those parts of the interface where seizure is complete are considered separately from those in areas where contact is localized and intermittent. Examination of worn tools suggests that two major wear processes take place on cemented carbide under each of these sets of conditions. It is believed to be unlikely that abrasion plays a major role in the wear of cemented carbide tools except in special circumstances.

The influence of powder-metallurgical processing variables in the production of cemented carbide tools is considered in relation to each of the main wear processes.