Comparison of the wear resistance of selected steels and cemented carbide cutting tool materials in machining wood

An experimental investigation is described where specimens of selected steels and cemented carbides are tested to simulate cutting green wood and cured wood. Extensive results are presented that show quantitatively the progressive wear of several Stellites, steels and cemented carbides as a function of time for sliding under wet and dry conditions.A simple theoretical analysis of tool wear that applies to cutting green wood with cemented carbide tools is described. The analysis, which indicates the important parameters in the wear process, is used to predict the effect of carbide particle size on wear rate. Comparisons are made between the predicted and experimentally determined wear rates for two groups of cemented carbide materials. Good agreement is found between experimental measurements and theoretical predictions. It is shown that wear depends on carbide particle size. Superior wear resistance of cemented carbides is attributed to the high hardness and low chemical reactivity of the carbide phase. The improved wear resistance of the Stellites is attributed to the low reactivity of the matrix.     

Effect of VC and (Ta,Nb)C on wear of WC–10Co based cemented carbides

Abstract

WC–Co cemented carbides, including small angular tungsten carbides particles, are used extensively to improve wear resistance. Some additives can affect mechanical and wear properties of these materials. In this study, the effect of VC and (Ta, Nb)C content on wear of WC–10Co were considered. The tests were performed at normal load of 230 N and sliding distance of 800 m up to 3200 m. Wear tests were carried out using dry sand/rubber wheel apparatus. Wear rate, standard and modified wear coefficients were calculated. The microstructures of prepared specimens were examined by optical microscopy. The morphological analysis of the worn surfaces was made by SEM. The results show that VC content has more effect than (Ta, Nb)C content on wear behaviour. Wear mechanism is different in the specimens, but removal of cobalt rich phase and fracture of carbide grains is clear in all of specimens. Abrasive wear is prevailing in all specimens.     

ZrN涂层刀具的滑动磨损特性研究

山东大学摘要:采用电弧离子镀法在硬质合金刀具表面制备了厚度为2.19~5.23μm的ZrN系列涂层,测定了涂层的显微硬度,并通过划痕试验和摩擦磨损试验考察了涂层与基体的结合强度及其摩擦磨损性能。在扫描电镜下观察磨损表面形貌,结果表明:ZrN系列涂层能够显著提高硬质合金刀具的表面硬度;涂层与基体的结合强度较高,划痕临界载荷高于60N;与此同时,电弧离子镀法ZrN系列涂层可以显著改善硬质合金刀具的耐磨性能。磨损机理主要是磨粒磨损和涂层的微剥落。     

The application of thin cemented carbide hardfacings to elements of card machines — a case history

The formation and behaviour of cemented carbide hardfacings a few micrometres thick deposited by the metallic surface fusion (MSF) process on parts of card machines are described. Rolls treated by the MSF process moving the processed cards are smoothed during service to produce flat featureless surfaces. In another application the overlay protects a steel spring from damage arising from fretting and sliding against a cemented carbide piercing punch. The deposit is worn out in a similar way, whilst the punches are slightly marred by “attrition wear”. In each application elements treated by the MSF process perform satisfactorily with a reduced failure rate.     

Resistance of a binderless cemented carbide to abrasion and particle erosion

A binderless cemented carbide has been evaluated in abrasion and erosion tests. The binderless carbide was compared with: SiC, Al₂O₃ and two conventional cemented carbides with 6% Co and different WC grain sizes (1 and 7 μm). In the abrasion tests, the materials were ground with silica, silicon carbide and diamond particles in the size range of 5–15 μm. The erosion tests were performed with 80, 200 and 600 μm silicon carbide erodents. The angle of impingement was 45° and the erodent velocity 70 m/s. In all tests, the conventional cemented carbides showed the highest, the binderless cemented carbide an intermediate and the ceramics the lowest wear resistance. Scanning electron and atomic force microscopy of the abraded surfaces revealed that the binderless cemented carbide was worn by a preferential removal of TiC grains. In erosion, the wear mechanism was largely plastic for the cemented carbides, whereas the ceramics were worn by micro-fracture. The SEM analysis also showed an impact scaling effect for the cemented carbides in erosion. This revised version was published online in August 2006 with corrections to the Cover Date.     

纳米硬质合金刀具切削Al/SiCp复合材料实验

SiC颗粒具有较高的硬度,使Al/SiCp复合材料在切削时刀具磨损剧烈。纳米硬质合金具有较高的硬度、韧性及良好的抗磨损能力。制备了纳米硬质合金刀具WC-7Co,对Al/SiCp复合材料进行了切削实验,研究了纳米硬质合金刀具磨损机理和Al/SiCp复合材料的切屑去除机理,以及刀尖处后刀面磨损值。研究认为,纳米硬质合金刀具磨损的机理为SiC颗粒的微切削作用引起的磨料磨损,及SiC颗粒对刀尖刃口的高频、断续冲击引起的微崩刃及微破损,Al/SiCp复合材料的切削实质是断续切削;Al/SiCp复合材料去除机理为切屑的崩碎去除;纳米硬质合金后刀面磨损值较普通硬质合金小30%~50%。     

An analytical and experimental investigation of the wear of cemented carbide cutting tools in the presence of dilute organic acids

A simple theoretical analysis of the tool wear process that applies to cutting green wood with cemented carbide tools is described. The analysis, which indicates the important parameters in the wear process, is used to predict the effect of binder volume fraction, carbide particle size, toolworkpiece contact force and the chemical reaction rate constant on wear rate. Comparisons are made between the predicted and experimentally determined wear rates for two types of cemented carbide tools in the presence of weak organic acids. Good agreement, is found that is thought to lend strong justification for the analysis.     

纳米硬质合金刀具切削Al/SiC_p复合材料的实验

针对SiC颗粒硬度高,切削Al/SiCp复合材料时刀具磨损剧烈,本文提出用具有较高硬度、韧性及良好抗磨损能力的WC-7Co制备纳米硬质合金刀具,并对Al/SiCp复合材料进行了切削实验。研究了纳米硬质合金刀具磨损机理和Al/SiCp复合材料的切屑去除机理,以及刀尖处后刀面磨损值。研究认为,纳米硬质合金刀具磨损的机理为SiC颗粒的微切削作用引起的磨料磨损,及SiC颗粒对刀尖刃口的高频、断续冲击引起的微崩刃及微破损;Al/SiCp复合材料的切削实质是断续切削;去除机理为切屑的崩碎去除;纳米硬质合金后刀面磨损值较普通硬质合金小30%～50%。实验表明,纳米硬质合金较普通硬质合金更适于加工Al/SiCp复合材料。     

The role of tool composition and tool geometry in controlling the surface finish in machining wood

An examination of several brazed cemented carbide tool inserts that were used in service for cutting cured (dry) pine is described. A laboratory test is also described where the relative resistance to chipping of the brazed tool inserts was measured.It is shown that tool wear occurs through a continuous increase in the tool cutting edge radius that produces a deterioration in the appearance of the machined surface. It is also shown that an increase in either the binder volume fraction or the tool wedge angle produces an increase in the energy absorbed on impact. It is suggested that if progressive wear determines the useful life of a cemented carbide cutting tool then a low volume fraction of binder is required whereas if tool edge chipping determines the useful life of a cutting tool then a large volume fraction of binder and a large tool wedge angle are required.     

Friction and wear in silicon nitride-steel and cemented carbide-steel pairs in lubricated sliding

Friction and wear tests between a stationary block and a rotating ring under high contact pressure of about 200 MPa were carried out at room temperature under lubrication with a light mineral oil at a sliding distance of 500 m. The block was silicon nitride and cemented carbide, and the ring was bearing steel. The effect of phosphorus and sulphur contained in the mineral oil on the friction, the roughness of the worn surface and the wear of the steel ring is discussed in relation to both pairs. Sulphur was effective in reducing the coefficient of friction of the cemented carbide block-steel ring pair, while phosphorus was successful in decreasing the wear of the steel ring paired with the silicon nitride block. The surface analysis of the steel ring using X-ray photoelectron spectroscopy (XPS) shows that the peak intensities of sulphur or phosphorus beneath the surface depend upon the material of the counterpart, silicon nitride or cemented carbide blocks.     

Wear Mechanism of Cemented Carbide Tool in High Speed Milling of Stainless Steel

Adhesion of cutting tool and chip often occurs when machining stainless steels with cemented carbide tools. Wear mechanism of cemented carbide tool in high speed milling of stainless steel 0Cr13Ni4 Mo was studied in this work. Machining tests on high speed milling of 0Cr13Ni4 Mo with a cemented carbide tool are conducted. The cutting force and cutting temperature are measured. The wear pattern is recorded and analyzed by high?speed camera, scanning electron microscope(SEM) and energy dispersive X?ray spectroscopy(EDS). It is found that adhesive wear was the dominant wear pattern causing tool failure. The process and microcosmic mechanism of the tool's adhesive wear are analyzed and discussed based on the experimental results. It is shown that adhesive wear of the tool occurs due to the wear of coating, the a nity of elements Fe and Co, and the grinding of workpiece materials to the tool material. The process of adhesive wear includes both microcosmic elements di usion and macroscopic cyclic process of adhe?sion, tearing and fracture.     

Particle erosion of cemented carbides with low Co content

Cemented carbides are well known for their high erosion resistance and are therefore used in many demanding applications involving erosion, such as grit blasting nozzles. A number of investigations on the erosive wear resistance of conventional cemented carbides have been published. The present paper is aimed at investigating the erosion resistance of a series of modern cemented carbides containing no or very small amounts of Co, so-called binderless carbides, and relating their performance to conventional sorts.

A series of binderless carbides with varying grain size (0.6, 2 and 5 μm) and binder content (0.25 and 1 wt.%) has been tested. The materials were eroded by SiC particles of three sizes (80, 200 and 600 μm) from four angles (90, 70, 50 and 30°) with a velocity of 70 m/s. Three conventional WC-Co grades of corresponding grain sizes were also tested, under identical test conditions.

The materials are ranked with respect to their erosion rate and scanning electron microscopy is used to analyse the worn surfaces. The influence of carbide grain size and binder amount on the wear behaviour is discussed.     

Mechanisms of dry wear of some martensitic steels

The basic wear mechanisms operating when two identical steel surfaces are rubbed against each other were studied to determine material parameters essential for wear resistance. Three simple model alloys, with the same basic properties as tool steels, were developed, containing three different predetermined volumes of M₇C₃ carbide, having approximately the same hardnesses after hardening and annealing, and approximately the same composition of the matrix.Unlubricated sliding wear tests were performed in air, using a pin-on-ring type machine. Normal force, sliding speed and sliding distance were varied. Friction force and temperature were recorded during the test and changes in weight of specimens were measured. The worn surfaces were carefully examined by scanning electron microscopy, in an attempt to classify the different wear mechanisms.It was found that corrosive wear dominates at low sliding speeds (2 m/min). Material annealed to a lower hardness had a lower wear resistance, irrespective of carbide content. The wear is characterized as mild.At high sliding speed (100 m/min) and especially for high normal forces, the wear was dominantly by a severe adhesive mechanism. Tempering to a lower hardness gave better wear resistance, which indicates that the room temperature hardness is not significant when a high contact temperature is reached. The influence of the carbide content was complex. The results indicate that a carbide free material is the most wear resistant, because of the more extensive occurrence of corrosive wear. Abrasives such as carbides in the more carbide rich alloys may possibly tear up protective corrosive layers and expose the steel to adhesive wear.     

Carbide tool wear mechanism in turning of Inconel 718 superalloy

Wear surfaces of the cutting tools are analyzed to study the wear mechanism of cemented carbide tools in turning in Inconel 718 superalloys. SEM and EPMA analyses indicated that the wear of carbide tools during high speed turning condition (V = 35 m min⁻¹) was caused by diffusion of elements (Ni or Fe) in workpiece into tool's binder (Co) by a grain boundary diffusion mechanism. This action weakened the bonding strength between carbide particles (WC, TiC, TaC) and the binder (Co). The carbide particles were then detached out of the cemented carbide tool by high flow stresses. The proposed grain boundary diffusion mechanism is also confirmed by theoretical analysis.     

Wear characteristics of titanium alloy Ti54 for cryogenic sliding applications

Cryogenic wear behaviour of Ti-5Al-4V-0.6Mo-0.4Fe (Ti54) alloy sliding against tungsten carbide is investigated at different speeds, loads and distances. Empirical models based RSM are developed to predict wear characteristics of Ti54 alloy as a function of sliding conditions. It is found that experimental and predicted results are in good agreement. Besides, cryogenic wear is substantially lower than dry wear. SEM and EDS analyses of worn surfaces and wear debris reveal that cryogenic sliding is significantly influenced by changing material properties along with boundary lubrication performance. The study has shown that modes in dry sliding are adhesion and delamination whereas in cryogenic sliding they are abrasion and delamination.     

Measurement of flank wear on cyclotron-activated tools

A method using cyclotron-induced radioactivity in cemented carbide turning tools was used to measure flank wear. The radioactivity is induced only in the wear area and is induced to a depth of 240 μm. Some of the parameters governing the induction and measurement of radioactivity are discussed.As the machining proceeds, the radioactive material from the tools is worn away and the remaining activity is measured by γ ray counting. Some correlation studies showed that the decrease in radioactivity is proportional to the square of the flank wear value measured optically. Therefore the method is more sensitive than the optical method and also is non-subjective.The method does not affect the tool performance nor is it affected by machining conditions, so that the total radioactivity loss at the end of tool life is independent of machining parameters. It has also been shown to be completely safe under workshop conditions.     

Effect of counter materials on coefficients of friction of TiN coatings with preferred grain orientations

In order to investigate the effect of counter materials on the coefficients of friction of TiN coatings with preferred grain orientations, the coefficients of friction against six counter materials (ball) were measured. The ball materials were aluminum (A1050), stainless steel (SUS304, SUS440C), bearing steel (SUJ2), carburized steel (SWRM10), cemented tungsten carbide (WC-Co) and alumina (Al₂O₃). After tests, the worn flat surfaces of balls and the wear tracks of TiN coatings were analyzed by the electron probe micro analysis (EPMA) and the auger electron spectroscopy (AES) to observe the Ti oxide film on each ball material and the adhesion of ball materials to the TiN coatings. The Ti oxide film was observed on the worn flat surfaces of the ball materials and the ball materials did not adhere to the TiN coatings in case that the low coefficients of friction were obtained.     

Effect of carbide size on the abrasion of cobalt-base powder metallurgy alloys

A study of the effect of carbide size on the abrasion resistance of two cobalt-base powder metallurgy alloys, alloys 6 and 19, was conducted using low stress abrasion with a relatively hard abrasive, A1₂O₃. Specimens of each alloy were produced with different carbide sizes but with a constant carbide volume fraction. The wear test results show a monotonie decrease in wear rate with increasing carbide size.Scanning electron microscopy of the worn surfaces and of wear debris particles shows that the primary material removal mechanism is micromachining. Small carbides provide little resistance to micromachining because of the fact that many of them are contained entirely in the volume of micromachining chips. The large carbides must be directly cut by the abrasive particles. Other less frequently observed material removal mechanisms included direct carbide pull-out and the formation of large pits in fine carbide specimens. These processes are considered secondary in the present work, but they may have greater importance in wear by relatively soft abrasives which do not cut chips from the carbide phase of these alloys. Some indication of this is provided by limited studies using a relatively soft abrasive, rounded quartz.     

高频摆动自润滑关节轴承故障分析与改进验证

对高频摆动工况下自润滑关节轴承GE20-1的故障分析显示:织物自润滑衬垫和内圈球面镀硬铬涂层耐磨损性能不佳,出现偏磨现象;磨损严重处衬垫磨穿,内圈球面涂层仅剩1～2μm.为提升轴承耐磨损性能,采用了PTFE纤维面密度约20.1％的CD2#衬垫与内圈球面硬质合金涂层相组合的改进方案,改进轴承GE20-2经1500 h寿命...     

WC-10Co-MoS2@Ni自润滑硬质合金与钛合金的摩擦学性能研究

为探究WC-10Co-MoS2@Ni自润滑硬质合金与TC4钛合金的摩擦学性能，通过热压烧结制备不同含量MoS2@Ni的硬质合金试样，采用扫描电子显微镜、三维轮廓仪、维氏硬度计等分析自润滑硬质合金的组织结构和力学性能，利用往复式摩擦试验机研究干摩擦、切削液环境和深冷环境下硬质合金与钛合金的摩擦学性能。结果表明：随着硬质合金中MoS2@Ni含量的增加，表面孔隙减少，力学性能缓慢下降；在干摩擦、切削液环境和深冷环境下，摩擦因数均随MoS2@Ni含量的增加而降低；钛合金和硬质合金在干摩擦时由于钛合金的黏附，阻碍了MoS2发挥润滑作用，磨损形式以黏着和氧化为主；在切削液环境中磨损形式以磨粒磨损和黏着磨损为主，而在深冷环境下减少了氧化和黏着，其磨损形式主要为磨粒磨损，并伴有分层磨损现象。