压力对放电等离子烧结硬质合金性能的影响

采用放电等离子技术(SPS)烧结WC-12Co硬质合金.主要研究了SPS烧结过程中压力对WC-12Co硬质合金致密化、显微组织及性能的影响,并探讨了压力对致密化和WC晶粒长大的影响机制.结果表明,提高SPS烧结压力提高了WC-12Co硬质合金的密度但导致了wC晶粒的长大.在较低的烧结温度下(1100℃)或较短的保温时间内(3 min),烧结压力对密度的影响较为显著.在较高的烧结温度(1150℃)时,烧结压力的提高导致合金中WC晶粒的明显长大.烧结压力对SPS烧结WC-12Co硬质合金力学性能的影响是通过对密度和WC晶粒尺寸的影响而起作用的.     

钨/钴氧化物SPS直接碳化原位合成超细WC-Co硬质合金

利用放电等离子烧结（SPS）技术将WO3、Co3O4和炭黑的混合粉原位合成为致密的WC—Co硬质合金栩种。研究了合成工艺和配碳量对合金物相、致密度及显微组织的影响，结果表明：在970℃以下的一定温度范围内，碳能快速地将Co3O4还原为Co，将WO3还原碳化为WC，温度继续升高发生烧结。含碳量低时．合金中存在Co3O4，C4和C铂Co3W3等缺碳相；只有碳量合适时，合金的物相为WC-Co，密度达到其理论密度范围，晶粒度在0．5μm左右。     

放电等离子烧结不同粒径匹配的WC-Co混合粉末

采用一种包括混合粉末真空预处理和放电等离子烧结(SPS)的新型烧结技术,制备超细晶WC-10Co硬质合金块体。采用场发射扫描电镜观察硬质合金的形貌和晶粒组织,采用三点弯曲法测量试样的断裂强度,利用显微硬度仪测量维氏硬度HV30且据此估算试样的断裂韧性KIC,并与真空烧结和直接SPS试样进行对比,同时还研究初始粉末中WC粉与Co粉的粒径匹配对SPS块体的显微组织和力学性能的影响。结果表明,与真空烧结和直接SPS相比,此种方法制备的WC-10Co合金晶粒细小、组织均匀,具有优异的综合力学性能,尤其是强度明显提高,硬度为1608HV30,断裂韧性为14.0MPa.m1/2,横向断裂强度为3100MPa;WC和Co粉末的粒径匹配对SPS块体的显微组织和力学性能具有较显著的影响。     

粉末原料对SPS法制备WC-6Co硬质合金组织性能的影响

以不同形貌结构的WC-6Co复合粉和传统湿磨制备的WC-6Co混合粉为原料,通过放电等离子烧结制备出WC-6Co硬质合金,采用SEM、显微硬度计、密度仪、钴磁仪和矫顽磁力计等对硬质合金的微观组织、力学和物理性能进行了表征。分析结果表明:采用喷雾转化、低温煅烧、原位合成制备的球形复合粉为原料,经SPS法制备所得的WC-6Co硬质合金中残留有较多孔隙,合金密度仅为14.21g/cm~3,将球形复合粉湿磨48h后制备的合金密度略有提升,但硬度和韧性较低。分别采用喷雾转化、低温煅烧加短时球磨、原位合成制备的松散型WC-6Co复合粉和传统湿磨制备的WC-6Co混合粉为原料,经SPS法制备的合金微观组织均匀、合金孔隙减少,两组合金的密度分别增加至14.77、14.73g/cm~3;显微硬度分别增大至2 045、1 929kg/mm~2,韧性分别为8.76、9.29MPa/m~(1/2)。     

放电等离子烧结制备超细晶WC-3Co硬质合金的组织和性能

采用高能球磨制备纳米WC-3Co粉末,再通过放电等离子烧结(spark plasma sintering,SPS)制备超细晶WC-3Co硬质合金。研究SPS工艺参数对合金致密度、显微组织和力学性能的影响,并对SPS和热压工艺(hotpressing,HP)进行对比。结果表明:SPS可实现WC-3Co粉末的低温快速致密化。升高温度或提高压力都使得合金的致密度提高,同时导致WC晶粒长大。SPS较HP升温速率快且烧结时间更短,合金组织更加均匀,在1 300℃保温5 min、烧结压力为40 MPa的条件下所制备的合金具有最佳综合性能,其平均晶粒度为0.32μm,相对密度、硬度、抗弯强度、断裂韧性分别为99.3%、2257 HV30、1 906 MPa、10.36 MPa.m1/2。而在1 450℃、压力为50 MPa、保压5 min条件下,热压合金的致密度、硬度和断裂韧性分别为99.6%、2 264 HV30和11.01 MPa.m1/2,但抗弯强度只有1 301 MPa,平均晶粒度为0.47μm。     

WC-6Co硬质合金SPS烧结工艺

以平均粒径约为30 μm,空心球壁厚约1.8 μm的空心球结构WC-6Co复合粉为原料,利用放电等离子烧结（SPS）技术制得不同烧结温度、保温时间、烧结压力工艺下的WC-6Co硬质合金.采用扫描电镜、钴磁仪等检测手段对合金的组织与性能进行表征分析.结果表明:随着烧结温度的升高,合金的致密度和硬度升高;在实验范围内合金密度与硬度随着保温时间的延长而增加,再趋于稳定;烧结压力对合金密度、硬度等性能影响不大.综合考虑合金性能,较好烧结工艺为:温度1 250 ℃、保温时间5 min、烧结压力50 MPa.该烧结工艺制得的合金的密度达14.69 g/cm3、断裂韧性达12.23 MPa·m1/2,其组织也很细很均匀.      

纳米硬质合金进展

综述了机械合金化、喷射转换、原位渗碳还原、共沉淀等多种WC Co纳米硬质合金粉末的制备方法 ,指出纳米WC Co粉末烧结过程中的致密化温度有明显的降低 ,晶粒长大趋势很强 ,同时给出了致密化后合金的显微组织、力学性能研究发展概况。提出目前存在的问题是烧结过程的晶粒长大的控制 ,采用新型的烧结手段实现快速烧结将是纳米硬质合金未来的发展方向     

放电等离子烧结制备钨钴硬质合金的研究现状

钨钴硬质合金因具有优异的硬度、耐磨性、强度和断裂韧性等综合性能被广泛应用。烧结是制备硬质合金最后也是最重要的步骤,近年来发展了多种硬质合金烧结技术。文章综述了放电等离子烧结(SPS)技术在硬质合金制备中的研究现状和发展趋势,认为目前针对SPS技术的研究多集中在温度因素对合金组织结构、性能的影响,而压力、气氛等因素的影响研究较少,故文章对压力、气氛等因素的影响研究也作了相应的归纳,最后对SPS技术在硬质合金领域研究应用发展前景进行了讨论。     

高温高压烧结制备WC-6Co硬质合金及其力学性能研究

以平均粒径约300 nm的复合粉为原料,采用高温高压烧结法在不同烧结温度和保温时间下制备了 WC-6Co硬质合金.通过X射线衍射仪、光学显微镜和显微硬度计研究了制备工艺对WC-6Co硬质合金晶体结构、显微组织和力学性能的影响.结果表明:试样烧结过程液相Co的流动性、WC颗粒重排和晶粒尺寸对合金密度、维氏硬度和断裂韧性起...     

TiC含量对WC-8Co超细晶硬质合金力学性能和微观组织的影响

采用放电等离子烧结技术制取不同TiC含量的WC-8Co硬质合金。分析了TiC含量对WC-8Co基硬质合金刀具材料的致密度、力学性能和微观组织的影响。实验结果表明,随着TiC含量增加,WC-8Co硬质合金常温综合力学性能先提高后降低,添加5%(质量分数)TiC的WC-8Co硬质合金具有较好的综合力学性能。当烧结温度和压力分别为1 250℃、50 MPa时,WC-5TiC-8Co硬质合金材料致密度、维氏硬度、断裂韧性以及室温下的抗弯强度分别达到98.85%、19.49 GPa、9.46 MPa·m~(1/2)和1 893 MPa。硬质合金致密化烧结曲线和组织显微形貌的分析结果表明,随着TiC含量增加,硬质合金的致密化烧结的起始温度向更低的温度偏移,Co相流动性变差,从而导致致密化烧结条件变差。试样中孔隙增多,是硬质合金维氏硬度和力学性能下降的主要原因。     

China's Major Non-ferrous Metals Imports & Exports

正~~     

Zinc Production by Province in 2014

正~~     

80% of Chinese Firms Purchasing Overseas Mines Ended up in the Red

<正>Minmetals Resources acquired the world’s largest copper mine under construction for USD5.85 billion.One after another,listed companies Jien Nickle,China Molybdenum and Chihong Zinc and Germanium raised money to get involved in overseas mining projects…SOEs and private enterprises are engaged in a frenzy of overseas mine purchasing.A reporter with Economic     

Copper Processing Profit Dropped Sharply,Copper Consumption Will Face Impact in the Second Half of the Year

正Judging from China’s copper consumption field,the biggest consumption unit is electric power,which accounts for 47%of total consumption;it is followed by light industry sector,including household electrical appliance,machinery,durable goods and hardware etc,which accounts for 22%of total consumption;followed by transportation field,     

Central Geological Prospecting Fund Newly Added 16.47 Million Tonnes of Bauxite in 2013

正In 2013,the Central Geological Prospecting Fund(CGPF)Project newly discovered 15 ore fields,including 3 large above ore fields,and 5medium sized ore fields.The reporter learned from the recently published"Annual Report of Central Geological Prospecting Fund Project(2013)"that,from 2006 to 2013 the CGPF     

Manufacturers of Copper Tube for Central Air Conditioner Use Face Mounting Pressure in the Final Quarter of the Year

正This year,the investment growth rate of real estate industry continued to slow down,sold area of commercial housing also dropped significantly,which brought huge pressure to the domestic air conditioning manufactures.In the first half of the year,by relying on high growth in national financial expenditure,along with investment in public infrastructure     

Xinjiang Ranks No.1 in Production of Primary Aluminum in China

正Kang Yi,Honorary Chairman of China Nonferrous Metals Industry Association,said recently at the Forum on Development of the Non-ferrous Metals Industry in Central and Western China held in Zhengzhou that,as more and more electrolytic aluminum factories in Xinjiang came into operation,the electrolytic aluminum output of Xinjiang had reached2,275,000 tons in the first 7 months this year,     

Shenhuo Coal Industry and Electricity Power Completed800,000 t/a Aluminum Project in Xinjiang

正"Xinjiang project has been completed according to schedule,but total completion and total start of production are two different concepts,after completion it still needs a gradual process of reaching production target."On the morning of November 3,Shenhuo Coal Industry and Electricity Power told investors the above statement on the investor interaction platform.     

Guangdong Metal Transaction Center has Become the Second Largest Precious Metal Transaction Platform Nationwide

正The reporter learned from Guangdong Province Precious Metal Transaction Center that in 2013the Center maintained healthy development momentum,and had become the second largest precious metal transaction platform in China in terms of market size;currently Guangdong is quickening steps of financial innovation for the Center,aiming to build a transaction center with international core competitiveness.     

Seven Rare Earth Projects Involving Close to 3 Billion Yuan Investment Landed In the HighTech Zone

正On May 22,Baotou Rare Earth Industry Cooperation Consultation MeetingProject Agreement-signing Ceremony was held in Ningbo,nearly 40 enterprises from Ningbo,Guangdong,Hunan,and Shanxi participated in project consultation.After multi-lateral communication,agreements were signed for a total of 7 rare earth projects successfully.