Matrix microstructure effect on the abrasion wear resistance of high-chromium white cast iron

The two-body abrasion resistance of high-chromium white cast iron was investigated as a function of cast iron microstructure. Different microstructures were obtained by means of heat treatment. The chromium and carbon content were chosen in order to have different matrix microstructures (austenitic, martensitic and ferritic) with the same amount of eutectic carbide (M₇C₃). The results show that the cast iron with an austenitic matrix has the best wear resistance. The good wear resistance of this material is due to strong work hardening of the austenitic matrix resulting in a hardness which exceeds that of other structures. The effect of abrasive paper deterioration on abrasion has also been investigated.     

高铬白口铸铁干滑动摩擦磨损特性的研究

研究了两种碳化物 ((Fe,Cr) 2 3 C6型碳化物和 (Fe,Cr) 7C3 型碳化物 )和 3种基体组织 (共析组织、马氏体组织和奥氏体组织 )的高铬白口铸铁与淬火 4 0Cr钢对磨时的干滑动摩擦磨损特性。试验结果表明 ,与(Fe,Cr) 2 3 C6型碳化物相比 ,(Fe,Cr) 7C3 型碳化物有利于提高高铬白口铸铁的耐磨性 ,降低其摩擦系数 ;在高接触应力情况下 ,与马氏体和奥氏体基体的合金相比 ,共析组织基体的合金具有更大的摩擦系数 ,其耐磨性也更好。     

Wear characteristics of TiC reinforced cast iron composites Part 2 – Abrasive wear

Abstract

The presence of carbide particles in metal matrix composites improves abrasive wear resistance properties. Abrasive wear characteristics of TiC reinforced cast iron composites have been investigated. The TiC particle size and distribution influence the wear properties of the composites. TiC reinforced cast iron composites possess better wear resistance properties than those of chromium cast irons with and without nitrogen.     

粉末冶金制备工艺对TiC增强高铬铸铁基复合材料性能的影响EI北大核心CSCD

采用高能球磨和真空烧结的方法制备TiC增强高铬铸铁(HCCI)基复合材料。利用SEM,DSC等方法对不同球磨时间的粉末进行分析,研究不同烧结温度对高铬铸铁基复合材料的显微组织、硬度及密度的影响,比较相同工艺下复合材料与高铬铸铁材料的耐磨性。结果表明:球磨12 h后的粉末颗粒大小趋于稳定,粉末活性提高,烧结性能改善,烧结试样中TiC均匀地分布在基体中。随着烧结温度的升高,复合材料内部晶粒逐渐长大,密度和硬度逐渐提高。在1280℃超固相线液相烧结的条件下烧结2 h后,致密度达94.17%,硬度和抗弯强度分别为49.2HRC和980 MPa。在销盘磨损实验中复合材料的耐磨性为单一高铬铸铁材料的1.52倍,磨损机制为磨粒磨损+轻微氧化磨损。     

Modifying high Cr–Mn cast iron with boron and rare earth–Si alloy

Abstract

By modifying 13Cr–4Mn (wt-%) white cast iron with boron and rare earth (RE)–Si complex, the carbide morphology of the iron can be changed from interconnected, coarse clusters of rods into a parallel distribution of isolated, fine rods, and the impact toughness of the iron can reach 6–7 × 10⁴ J m^?2. In a pin wear test, the relative abrasion resistance of the iron is 1·01 and in a repeated impact abrasive wear test it is 0·95, in comparison with 15Cr–3Mo cast iron. Thus, it is stated that modifying high Cr–Mn cast iron with boron and RE–Si complex is very cost effective, and has almost the same abrasion resistance, when compared with 15Cr–3Mo cast iron.

MST/957     

Nano-Scratching resistance of high-chromium white cast iron and its correlation with wear of cBN tool in machining

In this paper, a nano-scratch testing approach was used to measure and evaluate the abrasion wear resistance of high-chromium white cast irons in order to understand the wear mechanism in the interaction between the high-chromium white cast iron and the cBN cutting tool during the machining process. Scratch testing was performed on a nanoindentation instrument using a diamond indenter as the scratch tool. Linear multi-pass scratches in the same path were made on pre-worn surfaces of test materials. The correlation of the scratching resistance and tool wear measured from the machining is presented by the flank wear and maximum scratch depth. The appearance of the cutting edge on a cBN tool suggests that the abrasion wear is mainly related with a combined effect of the carbides and the matrix during machining the high-chromium white cast iron.     

Microstructure and wear resistance of spray formed and conventionally cast high‐chromium white iron

A billet of hypoeutectic high‐chromium white iron (19% Cr, 2.5% C) was spray formed using Gas‐to‐Metal Ratios (GMR) of 0.9, 1.0, and 1.1. Microstructural studies and dry sand rubber wheel abrasion tests were carried out, on the one hand, to compare between the spray formed and conventionally cast material and, on the other hand, to investigate the relationship between gas‐to‐metal‐ratio, eutectic carbide morphology and abrasion resistance. The spray formed material was characterized by a considerably finer carbide morphology (max. ?30 μm) than the conventionally cast material (max. 100–200 μm). The coarser carbide morphology is believed to be responsible for the superior abrasion resistance of the conventionally cast material. Although the carbide morphology of the spray formed material was only moderately influenced by the changes in the gas‐to‐metal‐ratio, there was a clear improvement in the abrasion resistance with decreasing gas‐to‐metal‐ratio. The improvement correlated with a decrease in the fraction of very fine (<1.5 μm) carbides, rather than with an increase in the mean carbide size.     

Microstructure and mechanical properties of high boron white cast iron

In this paper, high boron white cast iron, a new kind of wear-resistant white cast iron was developed, and its microstructure and mechanical properties were studied. The results indicate that the high boron white cast iron comprises a dendritic matrix and an interdendritic eutectic boride in as-cast condition. The distribution of eutectic boride with a chemical formula of M₂B (M represents Cr, Fe or Mn) and with a microhardness of HV2010 is much like that of carbide in high chromium white cast iron. The matrix includes martensite and a small amount of pearlite. After quenching in air, the matrix changes to martensite, but the morphology of boride remains almost unchanged. In the course of austenitizing, a secondary precipitation with the size of about 1 μm appears, but when tempered at different temperature, another secondary precipitation with the size of several tens of nanometers is found. Both secondary precipitations, which all forms by means of equilibrium segregation of boron, have a chemical formula of M₂₃(C,B)₆. Compared with high chromium white cast iron, the hardness of high boron white cast iron is almost similar, but the toughness is increased a lot, which attributes to the change of matrix from high carbon martensite in the high chromium white cast iron to low carbon martensite in the high boron white cast iron. Moreover, the high boron white cast iron has a good hardenability.     

粉末烧结法和铸造法制备ZrO2增韧Al2O3陶瓷颗粒增强高铬铸铁基复合材料及其耐磨性能

将粒径为1~2 mm的ZrO₂增韧Al₂O₃陶瓷颗粒(ZTA_p)、高铬合金粉末和黏结剂混合真空烧结制备蜂窝状预制体,再浇注高铬铸铁液制备出ZTA_p增强高铬铸铁基复合材料。采用SEM、EDS、XRD分析复合材料的界面微观结构和物相组成,通过三体磨损试验评价复合材料的耐磨性能。结果表明,烧结高铬铸铁基体在铸造过程中发生重熔,与铸造高铬铸铁基体呈冶金结合,ZTA_p与金属基体界面结合致密,无裂纹、气孔等缺陷。复合材料三体耐磨性能达到高铬铸铁的3倍以上。将该复合材料应用于制备磨辊件,经过5 000 h服役,柱状区和复合区在磨辊半径方向上的磨损量分别为8.2 mm、5.9 mm,预计寿命可达到高铬铸铁磨辊的2倍以上。      

Interactions between tungsten carbide (WC) particulates and metal matrix in WC-reinforced composites

A variety of experimental techniques have been used to investigate the interactions between tungsten carbide (WC–Co 88/12) particulates and the matrix in some new wear resistant cobalt-based superalloy and steel matrix composites produced by hot isostatic pressing. The results show that the chemical composition of the matrix has a strong influence on the interface reaction between WC and matrix and the structural stability of the WC particulates in the composite. Some characteristics of the interaction between matrix and reinforcement are explained by the calculation of diffusion kinetics. The three-body abrasion wear resistance of the composites has been examined based on the ASTM G65-91 standard procedure. The wear behavior of the best composites of this study shows great potential for wear protection applications.     

Erosive Wear and Wear Mechanism of in situ TiCp/Fe Composites

1.IntroductionMetal-based composite is a kind of environmental ma-terial that can be reused.It combines the beneficialproperties of the metal matrix,such as ductility,goodthermal and electrical conductivity and high toughness,with those of the reforcement phase[1~3].The latter isusually a ceramic,serving to increase the elastic modu-lus,shear strength and hot strength,fatigue and wearresistance.Its development has been widely studied[4~8].Wear of metal materials causes a tremendous loss of ec…     

Effects of Heat Treatment on Hardness and Dry Wear Properties of a Semi-Solid Processed Fe-27 wt pct Cr-2.9 wt pct C Cast Iron

EfFects of heat treatments on hardness and dry wear properties of a semi-solid processed Fe-26.96 wt pct Cr- 2.91 wt pct C cast iron were studied. Heat treatments included tempering at 500℃, destabilisation at 1075℃ and destabilisation at 1075℃ plus tempering at 500℃, all followed by air cooling. Electron microscopy revealed that, in the as-cast condition, the primary proeutectic austenite was round in shape while the eutectic M7C3 carbide was found as radiating clusters mixed with directional clusters. Tempering did not change the microstructure significantly when observed by scanning or transmission electron microscopy. Destabilisation followed by air cooling led to a precipitation of secondary M23C6 carbide and a transformation of the primary austenite to martensite. Precipitation behaviour is comparable to that observed in the conventionally cast iron. Tempering after destabilisation resulted in a higher amount of secondary carbide precipitation within the tempered martensite in the eutectic structure. Vickers macrohardness and microhardness in the proeutectic zones were measured. Dry wear properties were tested by using a pin-on-disc method. The maximum hardness and the lowest dry wear rate were obtained from the destabilisation-plus-tempering heat treatment due to the precipitation of secondary carbides within the martensite matrix and a possible reduction in the retained austenite.     

The influence of vanadium on fracture toughness and abrasion resistance in high chromium white cast irons

The influence of vanadium on wear resistance under low-stress conditions and on the dynamic fracture toughness of high chromium white cast iron was examined in both the ascast condition and after heat treatment at 500 °C. A vanadium content varying from 0.12 to 4.73% was added to a basic Fe-C-Cr alloy containing 2.9 or 19% Cr. By increasing the content of vanadium in the alloy, the structure became finer, i.e. the spacing between austenite dendrite arms and the size of massive M₇C₃ carbides was reduced. The distance between carbide particles was also reduced, while the volume fraction of eutectic M₇C₃ and V₆C₅ carbides increased. The morphology of eutectic colonies also changed. In addition, the amount of very fine M₂₃C₆ carbide particles precipitated in austenite and the degree of martensitic transformation depended on the content of vanadium in the alloy. Because this strong carbide-forming element changed the microstructure characteristics of high chromium white iron, it was expected to influence wear resistance and fracture toughness. By adding 1.19% vanadium, toughness was expected to improve by approximately 20% and wear resistance by 10%. The higher fracture toughness was attributed to strain-induced strengthening during fracture, and thereby an additional increment of energy, since very fine secondary carbide particles were present in a mainly austenitic matrix. An Fe-C-Cr-V alloy containing 3.28% V showed the highest abrasion resistance, 27% higher than a basic Fe-C-Cr alloy. A higher carbide phase volume fraction, a finer and more uniform structure, a smaller distance between M₇C₃ carbide particles and a change in the morphology of eutectic colonies were primarily responsible for improving wear resistance.     

Structure and abrasive wear resistance of R6M5 steel-tungsten carbide composite coatings

Features of the structure formation, composition, and abrasive wear resistance of R6M5 steel-tungsten carbide (R6M5-WC) composite coatings have been studied as dependent on the WC content. The introduction of ～20 wt % WC into the hardening composition leads to an increase in the fraction of M₆C carbide (in the form of eutectic inclusions with average size ～5.9 μm at grain boundaries and dispersed ～0.25 μm particles in the volume of grains), while a large proportion of metastable austenite (～88 vol %) is still retained. The R6M5-WC coatings exhibit high abrasive wear resistance, which is ensured by the γ → α′ martensite transformation during friction and a muiltimodal size distribution of hardening particles.     

Abrasive wear behaviour of hard powders filled glass fabric–epoxy hybrid composites

The effect of incorporation of tungsten carbide (WC) and tantalum niobium carbide (Ta/NbC) powders on three-body abrasive wear behaviour in glass fabric–epoxy (G–E) composites was investigated and findings are analysed. A vacuum assisted resin transfer moulding (VARTM) technique was employed to obtain a series of G–E composites containing different fillers (WC and WC + Ta/NbC). Dry sand rubber wheel abrasion test was carried out at 200 rpm speed. The effect of different loads (22 and 32 N) and abrading distances (from 135 to 540 m) on the performance of the wear resistance were measured. The wear volume loss of the composites was found increasing with the increase in abrading distances and under the same conditions the specific wear rate decreases. The hard powders filled G–E composite systems exhibit lower wear volume loss and lower specific wear rate as compared to unfilled G–E composite system. The features of worn surfaces of the specimen were evaluated at higher and lower abrading distances at load of 32 N were using scanning electron microscope (SEM) and results indicate more severe damage to matrix and glass fiber in unfilled composite system as compared to hard powder filled composites.     

Effects of Lubricant Condition and Tool Wear in Hard Turning of Novel-Abrasion-Resistance (N-AR) Cast Iron

Advanced materials, such as high abrasion resistant cast iron, have great applications for abrasive and erosive environments. Since the amount and the hardness of the microstructural carbides constituents in this material is extremely high, the abrasion-resistance cast iron is generally difficult to be machined with traditional cemented carbide tool. The hard and abrasive particles in this material can remarkably shorten the cutting tool life through abrasion of tool face and deterioration of cutting edge. In this article, Cubic Boron Nitride (CBN) cutting tool has been used to machine a novel-abrasion-resistance (N-AR) cast iron. The performances of CBN tool under different lubrication conditions were evaluated in view of tool wear, cutting force, and surface roughness (Rz). Further more, the wear rate of CBN tool under different machining condition and the mechanism of the CBN tool in machining of this type of work materials has also been investigated.     

Reinforcement of Hadfield steel matrix by oriented high‐chromium cast iron bars

To attain a wear‐resistant material compatible with high hardness and high toughness, Hadfield steel matrix was reinforced by oriented high chromium cast iron bars, through inserting high chromium alloys flux‐cored welding wires into Hadfield steel melt at 1500 ± 10 °C. The obtained composites were investigated by XRD, SEM, micro‐hardness, three‐body abrasion wear and impact toughness testers. The results show that the alloy powders inside the flux‐cored welding wires can be melted by the heat capacity of Hadfield steel melt and in situ solidified into high chromium cast iron bar reinforcements tightly embedded in the matrix. The micro‐hardness of reinforcements of the water‐quenched composite is about four times higher than that of the matrix. The impact toughness of the water‐quenched composite is higher than that of the as‐cast composite and lower than that of Hadfield steel, and its fracture mechanism is very complicated and refers to brittle and ductile mixture fracture mode. The excellent impact toughness and better wear resistance of the water‐quenched composite are attributed to combine fully the advantages and avoid the drawbacks of both Hadfield steel and high chromium cast iron. Additionally, in industrial application, the pulverizer plate produced by this composite, has also better wear resistance compared to the reference Hadfield steel pulverizer plate.     

Abrasive Wear Model for Al2O3 Particle Reinforced MMCs Using Genetic Expression Programming

In this investigation, a new model was developed to predict the wear rate of Al2O3 particle-reinforced aluminum alloy composites by Genetic Expression Programming (GEP). The training and testing data sets were obtained from the well established abrasive wear test results. The volume fraction of particle, particle size of reinforcement, abrasive grain size and sliding distance were used as independent input variables, while wear rate (WR) as dependent output variable. Different models for wear rate were predicted on the basis of training data set using genetic programming and accuracy of the best model was proved with testing data set. The two-body abrasive wear tests of the specimens was performed using a pin-on-disc abrasion test apparatus where the sample slid against different SiC abrasives under the loads of 2N at the room conditions. The test results showed that GEP model has produced correlation coefficient (R) values about 0.988 for the training data and 0.987 for the test data. The predicted wear rate results were compared with experimental results and found to be in good agreement with the experimentally observed ones.     

粗晶TM52钢结硬质合金的冲击磨料磨损性能研究

系统对比研究了粗晶粒TM52钢结硬质合金与分别采用真空烧结和低压烧结制备的细晶粒TM52钢结硬质合金在不同冲击功工况下的抗磨料磨损性能与行为,并在对磨损面形貌进行电镜观察分析的基础上探讨了粗晶粒TM52钢结硬质合金的磨损机理。研究发现,粗晶TM52合金的抗磨料磨损性能随着冲击功的逐步提高呈现先下降后增强的变化规律,这与其高锰钢基体在高冲击功条件下的高硬化速率及硬化效果更快、更充分有关。相对于细晶粒钢结硬质合金,粗晶粒TM52钢结硬质合金在抗冲击磨料磨损方面具有明显的性能优势,尤其在高冲击功(3~4J/cm~2)条件下,耐磨性能可提高40%~80%。在此工况下磨损机制主要为碾碎性磨料磨损、擦伤式磨料磨损和疲劳磨损,凿削式磨料磨损不明显。     

Grain size effect on wear resistance of WC-Co cemented carbides under different tribological conditions

The grain-size dependence of wear resistance of WC-Co cemented carbides(with mean WC grain sizes of 2.2 μm,1.6 μm,0.8 μm and 0.4 μm,respectively) was investigated under different tribological conditions.The results showed that the grain size had opposite effects on wear resistance of the cemented carbides in dry sliding wear and microabrasion tests.In the former condition,with decrease of WC grain size hence the increase of hardness,plastic deformation,fracture,fragmentation and oxidation were all mitigated,leading to a drastic decrease in the wear rate.In the latter condition,pull-out of WC grains after Co removal dominated the wear,so that the hardness of cemented carbide was not a core factor.As a result,the wear resistance of the cemented carbide generally showed a decreasing trend with decrease of the grain size,except for a slight increase in the ultrafine-grained cemented carbide.Single-pass scratching of the cemented carbides under various loads indicated the same failure mechanism as that in the sliding wear tests.Furthermore,the reasons for severe surface oxidation of the coarse-grained cemented carbides were disclosed.