热处理对高铬铸铁基蜂窝陶瓷复合材料耐磨性的影响

通过传统重力浇注工艺,用高铬铸铁金属溶液铸渗ZrO2增韧Al2O3(ZTA)陶瓷颗粒蜂窝状预制体,从而获得高铬铸铁基蜂窝陶瓷复合材料。将复合材料在930℃、980℃、1 030℃、1 080℃温度下淬火,并分别在230℃、330℃、430℃、530℃时回火,研究了热处理条件对高铬铸铁基蜂窝陶瓷复合材料组织及三体磨料磨损性能的影响。研究结果表明:在相同回火温度条件下,随着淬火温度的升高,复合材料硬度升高,其耐磨性也随之升高;在相同淬火温度条件下,随着回火温度的升高,材料的硬度及耐磨性能也随之升高,两者达到一定温度后其硬度及耐磨性都下降,材料耐磨性与材料的硬度变化趋势一致。最终得到复合材料的最佳热处理工艺为:1 030℃×2h,空冷+530℃×0.5h。     

活化烧结制备TiC-Ni金属陶瓷复合材料及其性能

采用球磨法制备TiC/Ni金属陶瓷复合材料粉末,粉末在3000kg/cm2压力下压制成形,在1340℃进行真空液相烧结.对活化粉末进行XRD分析和TEM分析,采用普通金相显微镜对烧结体的微观组织进行分析,用三点弯曲试验测试其抗弯强度,在硬度测试仪上测试其硬度.结果表明:TiC/Ni金属陶瓷复合材料可在1340℃进行烧结制备,球磨初期粉末烧结体的微观组织随着粉体球磨时间的延长逐渐得到改善;过分延长球磨时间,则由于粉末中引入大量的缺陷和严重加工硬化而导致粉末压缩性能下降,进而抑制了材料的烧结致密化能力,使得烧结体的孔隙率急剧上升,力学性能相应下降.     

高铬铸铁耐磨材料在泥沙磨损条件下耐磨性影响因素分析

分析了碳化物形态与分布、基体组织和稀土变质处理对高铬铸铁耐磨材料在泥沙磨损条件下的耐磨性影响。结果表明：碳化物的形态和分布对高铬铸铁的耐磨性有直接影响,块状或短杆状且分布均匀的碳化物对提高材料的耐磨性有利,网状或长针状碳化物对耐磨性不利;在泥沙磨损试验条件下,提高高铬铸铁中基体组织的显微硬度和基体组织与碳化物的结合强度有利于提高高铬铸铁材料的耐磨性;稀土元素的加入,使高铬铸铁的晶粒细化,碳化物颗粒变得细小,分布更为均匀,有利于提高高铬铸铁在泥沙磨损条件下的耐磨性。     

构型陶瓷/钢铁耐磨复合材料研究进展

近年来,陶瓷颗粒非均匀分布增强钢铁基复合材料(构型复合材料)由于具有优异的耐磨性,成为国内外高性能耐磨材料研究和应用的热点.对构型复合材料耐磨性的研究进行了综述,认为在无冲击磨料磨损工况下,构型复合材料的耐磨性显著高于常规陶瓷颗粒均匀分布增强复合材料,其耐磨性顺序按照基体排列为:高铬铸铁基>合金钢基>高锰钢基复合材料;陶瓷/钢铁界面结合强,则复合材料耐磨性高;按照陶瓷颗粒排序是:WC>(TiC,ZTA)>Al2O3增强复合材料;ZTA中ZrO2含量高,则耐磨性好.在高冲击磨料磨损工况下,构型复合材料耐磨性远不如无冲击工况下的耐磨性,有的甚至比基体差;合金钢基复合材料耐磨性比高锰钢基稍高.综述了不同工况下构型复合材料的磨损机理,并提出了构型陶瓷/钢铁复合材料的研究方向.     

烧结温度对粉末冶金铁基材料组织与性能的影响

目的 利用粉末冶金工艺制备了Fe-Ni-Cu-Cr-Si-C(石墨)材料,并且研究烧结温度对材料显微组织、硬度、致密度、耐磨性的影响.方法 在1050,1100,1150℃烧结温度下烧结2 h后得到了3组样品,并利用光学显微镜、扫描电子显微镜、X射线衍射仪对样品进行组织结构分析.采用布氏硬度计和电子天平分别对样品进行硬度和密度测试,采用球盘磨损实验机对样品进行耐磨性分析.结果 随着烧结温度的升高,晶粒尺寸逐渐变大.当烧结温度从1050℃增大到1100℃时,奥氏体量增加,表明奥氏体的转变在进行,且硬度和致密度也逐渐增加.烧结温度从1100℃增大到1150℃时,硬度的增速放缓,且在1150℃时硬度达到最大值,烧结温度在1150℃时耐磨损性能最好.随着烧结温度的升高,摩擦因数逐渐减小,由于材料的硬度增大,基体更有能力支撑表面润滑膜,从而表现出更加优越的耐磨损性能.结论 在1050～1150℃范围内,烧结温度的提高可以改善显微组织,提高组织的硬度、致密性、耐磨性.     

球磨时间对热压烧结制备TiC-CoCrFeNi复合材料微观组织及力学性能的影响

采用机械合金化-热压烧结法,制备TiC-CoCrFeNi复合材料,研究球磨时间对材料微观组织及力学性能的影响。结果表明:Co,Cr,Fe和Ni粉体在球磨10h后形成fcc结构的单相固溶体。经1200℃/1h热压烧结后,烧结体中生成TiC和Cr7C3结构的碳化物,并弥散分布于CoCrFeNi固溶体中。球磨时间显著改变了烧结体中碳化物的数量和尺寸,进而影响材料的力学性能。在球磨10h时,烧结体中纳米级TiC相急剧增多,此时复合材料的硬度(671HV)和屈服强度(1440MPa)达到最大值。     

高能球磨法制备Ag-Cr触头合金

采用机械合金化方法制备Ag-Cr合金,研究不同球磨时间对粉末晶体结构、晶粒尺寸、微观应变和表面形貌的影响,不同转速、相同球磨时间对粉末结构的影响以及合金密度、硬度随烧结温度的变化。结果表明:当机械球磨给予合金粉末足够的能量,就能够让铬固溶在银中形成过饱和固溶体;随着高能球磨时间的延长,晶粒逐渐细化、微观应变量逐渐变大,球磨65h时,平均晶粒尺寸为18.40nm,微观应变量为0.14%。烧结温度为850℃时,合金维氏硬度值约达99,密度达9.35g/cm3。     

TiC_(0.7)N_(0.3)增强ZrO_2基复合材料的微观结构及力学性能

为提高ZrO2基复合材料硬度,采用热压烧结法制备了TiC0.7N0.3/ZrO2复合材料,并研究了TiC0.7N0.3颗粒增强相对复合材料的物相组成、微观结构和力学性能的影响。结果表明:TiC0.7N0.3的添加具有稳定四方相ZrO2(t-ZrO2)的作用,能增加TiC0.7N0.3/ZrO2复合材料中t-ZrO2的含量,提高断裂韧性。随着热压烧结温度的升高和TiC0.7N0.3含量的增加,复合材料的硬度升高。1 400℃下热压烧结时,TiC0.7N0.3发生部分分解,分解的N与被还原的ZrO2反应生成ZrN,提高了复合材料的硬度。1 400℃下热压烧结后的35wt%TiC0.7N0.3/ZrO2复合材料的相对密度达99.9%,维氏硬度达17 GPa。而1 300℃下热压烧结后,复合材料断裂韧性较高,为6.48 MPa·m1/2。研究结果为TiC0.7N0.3/ZrO2复合材料的组织控制及性能改进提供了参考。     

纳米TiC颗粒弥散增强超细晶钨基复合材料的组织结构与力学性能

采用高能球磨和热压烧结的方法成功制备了纳米TiC颗粒弥散增强超细晶W基复合材料,并对其组织结构、室温力学性能进行了研究.研究结果表明,当纳米TiC颗粒含量较小时,高能球磨可以使TiC颗粒均匀分散到W基体中,烧结后,TiC颗粒尺寸约100nm,当纳米TiC颗粒含量较高时,局部出现团聚现象;纳米TiC的加入强烈的阻碍了W晶粒的长大并使复合材料的断裂模式由沿晶断裂为主向穿晶断裂为主转变,提高了材料的力学性能;在TiC含量为1%(质量分数,下同)时,材料的致密度、维氏显微硬度、弹性模量、抗弯强度分别达到98.4%、4.33、396GPa、1065MPa.纳米TiC颗粒对复合材料的强化机制主要是细晶强化和晶界强化.     

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。      

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.     

TiCp/Cr15高铬铸铁复合材料的制备与性能

以TiC_p粉末和水雾化Cr15高铬铸铁粉末为原料,采用粉末冶金液相烧结技术制备TiC_p增强高铬铸铁复合材料。研究了TiC_p含量对高铬铸铁的物相组成、显微组织和力学性能的影响。研究结果表明,全致密的TiC_p增强高铬铸铁基体复合材料的构成相为TiC、M₇C₃型碳化物、马氏体和少量奥氏体;随着TiC_p添加量增大,金属基体逐步呈孤岛状,并在其中析出越来越多的M₇C₃型碳化物,同时TiC_p逐步呈连续网状分布;同时,其硬度稳步提升,而抗弯强度和冲击韧性降低。当TiC_p添加量为20wt%时烧结态复合材料具有最佳综合力学性能。此时硬度为HRC 66.8 ,冲击韧性为6.86 J/cm2,抗弯强度为1 343.10 MPa。当TiC_p添加量为25wt%时硬度达到最大值HRC 67.20 。      

B4C包覆ZTA颗粒增强铁基复合材料制备与性能

ZTA (ZrO₂增韧Al₂O₃)陶瓷颗粒表面包覆B₄C微粉,将其制备成蜂窝状结构陶瓷预制体。采用传统重力浇注工艺将陶瓷预制体与熔融的高铬铸铁(HCCI)金属溶液进行复合,获得ZTA陶瓷颗粒增强高铬铸铁基复合材料。对复合材料中ZTA陶瓷颗粒增强相与高铬铸铁基体之间的界面及复合材料的耐磨料磨损性能进行了研究。结果表明,ZTA陶瓷颗粒与高铬铸铁界面结合处形成了明显的过渡区域,界面过渡区域的存在提高了陶瓷颗粒与金属基体的结合,从而提升了复合材料的整体稳定性能。同时,三体磨料磨损试验表明该复合材料的耐磨料磨损性能是高铬铸铁的3.5倍左右。     

Fabrication and Characterization of FeNiCr Matrix-TiC Composite for Polishing CVD Diamond Film

Dynamic friction polishing (DFP) is one of the most promising methods appropriate for polishing CVD diamond film with high efficiency and low cost.By this method CVD diamond film is polished through being simply pressed against a metal disc rotating at a high speed utilizing the thermochemical reaction occurring as a result of dynamic friction between them in the atmosphere.However, the relatively soft materials such as stainless steel, cast iron and nickel alloy widely used for polishing CVD diamond film are easy to wear and adhere to diamond film surface, which may further lead to low efficiency and poor polishing quality.In this paper, FeNiCr matrix-TiC composite used as grinding wheel for polishing CVD diamond film was obtained by combination of mechanical alloying (MA) and spark plasma sintering (SPS).The process of ball milling,composition, density, hardness, high-temperature oxidation resistance and wear resistance of the sintered piece were analyzed.The results show that TiC was introduced in MA-SPS process and had good combination with FeNiCr matrix and even distribution in the matrix.The density of composite can be improved by mechanical alloying.The FeNiCr matrix-TiC composite obtained at 1273 K was found to be superior to at 1173 K sintering in hardness, high-temperature oxidation resistance and wearability.These properties are more favorable than SUS304 for the preparation of high-performance grinding wheel for polishing CVD diamond film.     

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.     

The effect of production parameters on microstructure and wear resistance of powder metallurgy Al–Al2O3 composite

Aluminum matrix composite is one of the most conventional types of metal matrix composites. This paper deals with the effect of production parameters on wear resistance of Al–Al₂O₃ composites. Alumina powder with a particle size of 12, 3 and 48 μ and pure aluminum powder with particle size of 30 μ were used. The amount of added alumina powder was up to 20%. Ball milling was utilized to blend the powders. The range of sintering temperature and time were 500, 550 and 600 °C and 30, 45, 60 and 90 min respectively. It was found that increasing sintering temperature results in increasing density, hardness and wear resistance and homogenization of the microstructure. However at certain sintering temperatures and time, considerable grain growth and reduction of hardness value occurred, leading to the degradation of wear resistance. The results showed that at high alumina content, relative density of the composite increases. However, after raising the particle size of alumina, relative density initially increases and then drops to lower values. Increasing weight percent of alumina powder leads to higher hardness and consequently improves the wear resistance of Al–Al₂O₃ composite. The use of fine alumina particles has a similar effect on hardness and the wear resistance. Finally, a finer grain size was observed, at high amount and low size of the reinforcement particle.     

Synthesis and characterization of TiC-reinforced iron-based composites Part II on mechanical characterization

The hardness, impact toughness and wear resistance properties of Fe-TiC composites, synthesized by aluminothermic reduction of an industrial waste, have been evaluated. The wear resistance property of the composites has been compared with some standard wear resistant materials. It has been found that the wear resistance property of the Fe-TiC composites with mostly pearlitic, fully pearlitic and pearlitic plus cementite type matrix with about 7 to 8 vol% TiC is better than that of a standard high chromium iron. The wear resistance property of ferritic and mostly ferritic type matrix with about 5 vol% TiC is better than that of a standard bearing steel.