载荷对高铬铸铁磨料磨损的影响

对不同载荷作用下的高铬铸铁在耐磨实验机上进行了磨料磨损试验;对在不同的载荷作用下碳化物对基体的保护作用与碳化物的剥离进行了相关的分析。结果表明载荷在一定值以下磨损较为缓慢,当载荷超过一定值时,磨损急剧加剧,随着载荷的增加“尺寸较小”的碳化物首先剥离基体,当载荷继续增大时,“尺寸较大”的碳化物也剥离基体并有碎裂现象。因此,要求高铬铸铁中的碳化物不仅要分布均匀,而且尺寸也要合适。     

碳化物对高铬铸铁高应力磨料磨损的影响

对不同载荷作用下的高铬铸铁在耐磨实验机上进行了磨料磨损试验;对在不同的碳化物时基体的保护作用与碳化物的剥离进行了相关的分析.结果表明载荷在一定值以下磨损较为缓慢,当载荷超过一定值时,磨损急剧加剧,随着载荷的增加尺寸较小的碳化物首先剥离基体,当载荷继续增大时,尺寸较大的碳化物也剥离基体并有碎裂现象.这要求高铬铸铁中的碳化物不仅要分布均匀,碳化物的尺寸也要合适.     

碳化物在高铬铸铁高应力磨料磨损中的影响

对不同载荷作用下的高铬铸铁在耐磨实验机上进行了磨料磨损试验;对在不同的碳化物对基体的保护作用与碳化物的剥离进行了相关的分析.结果表明载荷在一定值以下磨损较为缓慢,当载荷超过一定值时,磨损急剧加剧,随着载荷的增加"尺寸较小"的碳化物首先剥离基体,当载荷继续增大时,"尺寸较大"的碳化物也剥离基体并有碎裂现象.这要求高铬铸铁中的碳化物不仅要分布均匀,碳化物的尺寸也要合适.     

高铬铸铁中碳化物相抗磨作用的“尺寸效应”

在以显微切削为主要机制的二体磨制磨损系统中，研究了不同铸型条件下碳化物尺寸的变化对高铬铸铁耐磨性的影响。结果表明，高铬铸铁中碳化物相的抗磨作用具有“尺寸效应”，即在碳化物数量一定时，过小的碳化物尺寸将影响碳化物相抗磨作用的发挥，大幅度地降低高铬铸铁的耐磨性。     

材料复合视角下的高铬铸铁组织结构

高铬铸铁可以看成是由增强相和基体相组成的颗粒增强复合材料,从材料复合的角度对高铬铸铁磨料磨损进行了分析。结果表明:高铬铸铁中碳化物保护基体减少受磨料冲击和磨损,基体固定和支撑碳化物以免碳化物失稳或被拔出;碳化物尺寸太小容易被冲断或被连根挖出,尺寸太大脆断倾向大;碳化物间距过大,磨料落在基体上的机率增大,间距过小时又使得基体难于固定和支撑;碳化物体积分数过小不耐磨,过大会使基体过于弱化;不同组织类型的基体性能差异很大,其中马氏体基体最耐磨但韧性差。结合分析结果,综述了高铬铸铁中碳化物和基体的主要控制方法。     

改善高铬铸铁力学性能的研究方法

综述了高铬铸铁的基体组织和碳化物，介绍了近年来国内外研究学者最常用的提高高铬铸铁力学性能的方法：热处理和合金化。发现高铬铸铁的高磨损性能及其他力学性能主要取决于共晶碳化物的数量、类型及基体组织。可通过热处理、合金化等方法，在高铬铸铁凝固过程中改变高铬铸铁的基体结构、改善碳化物的形貌、控制碳化物的生长等方面对高铬铸铁的性能进行优化。最后，对未来的研究方向提出了展望。     

高铬铸铁基体组织对冲击磨损的影响

研究了具有一定碳化物体积分数而基体组织不同的高铬铸铁在不同冲击磨损条件的磨损特性，结果表明，磨料改变引起磨损失重，磨损次序和磨损失效机制的变化。     

含钼镍高铬铸铁中温三体磨损性能研究

在中温三体磨损工况下,研究了含钼镍高铬铸铁的磨损性能以及钼对高铬铸铁组织、结构和力学性能的影响规律。实验表明,含钼镍高铬铸铁的磨损方式主要为显微切削、犁沟及部分塑性变形引起的剥落和碳化物断裂。钼含量为1.27%试样的显微组织中碳化物细小且分布较为均匀致密,对基体有很好的保护作用,硬度达64.4 HRC,具有最佳的中温三体磨损性能。     

B对Cr27型高铬白口铸铁组织和性能的影响

通过改变加入硼元素的含量,研究Cr27型高铬白口铸铁中碳化物和基体的改变对硬度、冲击性能以及耐磨性的影响,并对材料的冲蚀磨损机理做了进一步的解释。结果表明:随着硼含量的增加,碳化物逐渐粗化,高铬白口铸铁的冲蚀性能逐渐恶化。当硼含量为0.5%时,铸铁的综合力学性能达到最佳。     

冷却速度对高铬铸铁凝固组织及耐磨性的影响

研究了高铬铸铁在凝固过程中冷却速度对微观组织及耐磨性的影响。结果显示,高铬铸铁在凝固过程中,快的冷却速度使碳化物硬质相的硬度降低,韧性提高;冲蚀磨损的作用下,不易脱落和脆性断裂,因而对基体有较好的保护作用,使得单位面积上体积损失率变小。高铬铸铁在凝固过程中的冷却速度越快,其抗冲蚀磨损的能力就越强。     

热处理对含铬低碳钢组织与性能的影响

研究了低碳含铬钢950℃淬火后650℃回火,不同的保温时间下,Cr对低碳合金钢调质后性能的影响,并和不加Cr相同成分的钢作了对比。研究发现,当保温时间以2.5 min/mm计算时,加Cr钢的力学性能低于不加Cr同成分的钢,金相组织观察发现Cr能够有效提高低碳合金钢的淬透性,淬火后即使钢板的心部也能获得贝氏体组织,为后续的回火做好组织准备。然而在回火后容易形成M23C6及M7C3碳化物,其稳定性较差,容易聚集长大,且形态为条状,拉伸时容易弯曲破裂,严重破坏钢板的连续性,降低钢板的强度及塑性。对不同回火保温时间的含Cr钢的二次相粒子析出行为研究发现,以1 min/mm计算保温时间时,没有发现含Cr碳化物的析出,但随着保温时间的增加,Cr钢中的含Cr碳化物快速析出,并迅速长大,尤其是以3 min/mm计算保温时间下,含Cr碳化物尺寸已经达到了300 nm。因此对含Cr低碳合金钢,必须采用合适的调质工艺,适当缩短回火保温时间,以降低碳化物的聚集长大,避免回火后强度和塑性的同时降低。     

Influence of the cemented carbide specification on the process force and the process temperature in grinding

Cemented carbides are hard and brittle materials. Their material properties are adjusted by their chemical composition, in particular their average hard phase grain size and their binder fraction. The research paper focusses on grinding of cemented carbides with cobalt (Co) as binder and tungsten carbide (WC) as hard phase material. Within the research paper, it is discussed if and to what extent the cemented carbide composition affects the occurring thermo-mechanical load collective in the grinding process. In particular, the influence of the average WC grain size and the cobalt fraction on the thermo-mechanical load collective is investigated and explained by the cemented carbide material properties. The results of the publication contribute to a knowledge-based design of cemented carbide grinding processes.     

Wear damage of cemented carbides with different combinations of WC mean grain size and Co content. Part I: ASTM wear tests

In the present work we made and examined cemented carbides characterized by very different WC grain sizes varying from near-nano with a WC mean grain size of about 200 nm to coarse-grain with a WC mean grain size of about 4.5 μm and Co contents varying from 3 to 24 wt.%. The major objective of the present work was to examine the wear damage, wear behavior and wear mechanisms of cemented carbides having nearly the same hardness but greatly varying with respect to their WC grain size and Co content in the high-load ASTM B611 test and low-load G65 test.Both the hardness and resistance to fracture and micro-fatigue of cemented carbides play an important role in the wear damage by use of the high-stress ASTM B611 test when the carbide surface is subjected to alumina particles at high loads. In this case, the wear-resistance increases with increasing the WC mean grain size and decreasing the Co content at nearly the same hardness of the different cemented carbides. The submicron and near-nano cemented carbides are characterized by lower wear-resistance in comparison with the coarse-grain grade due to their reduced fracture toughness, fracture resistance and resistance to micro-fatigue.The Co mean free path in the carbide microstructure plays an important role with respect to wear-resistance in the low-stress ASTM G65 test when the carbide surface is subjected to gentle scratching by abrasive silica particles. The predominant wear of the thick Co interlayers leaving unsupported WC grains plays the decisive role in the wear behavior of the coarse-grain grade resulting in its low wear-resistance. In contrast to the ASTM B611 test the wear rate decreases with decreasing the WC mean grain size and increasing the Co content due to the corresponding reduction of Co mean free path in the carbide microstructure. As a result, the wear-resistance of the near-nano grade in the ASTM G65 test is the best of all in spite of its reduced fracture toughness.Phenomena of micro-fatigue, micro-fracturing and micro-chipping are found to play a decisive role in the wear damage of cemented carbides if they are subjected to abrasion wear, high loads and severe fatigue.     

Microstructure and wear resistance of highchromium cast iron containing niobium

In the paper, the effect of niobium addition on the microstructure, mechanical properties and wear resistance of high chromium cast iron has been studied. The results show that the microstructure of the heattreated alloys is composed of M7C3 and M23C6 types primary carbide, eutectic carbide, secondary carbide and a matrix of martensite and retained austenite. NbC particles appear both inside and on the edge of the primary carbides. The hardness of the studied alloys maintains around 66 HRC, not significantly affected by the Nb content within the selected range of 0.48%-0.74%. The impact toughness of the alloys increases with increasing niobium content. The wear resistance of the specimens presents little variation in spite of the increase of Nb content under a light load of 40 N. However, when heavier loads of 70 and 100 N are applied, the wear resistance increases with increasing Nb content.     

S390粉末高速钢真空气淬中纳米碳化物的析出

S390粉末高速钢经1180℃真空加热气冷(4×105Pa)、1230℃真空加热气冷(6×105Pa)后得到以下贝氏体为主的显微组织。结果表明,在片状下贝氏体中部析出成排碳化物是碳按下坡扩散机制和按dr/dt∝t-1/2方程长成260 nm×65 nm椭球状。在残留合金碳化物边缘析出纳米椭球状碳化物是按碳上坡扩散在离碳化物某处形成碳浓度峰,并处于最大过冷条件下进行析出的机制。     

一种改善耐磨高锰钢碳化物形态的热处理工艺

探讨一种改善耐磨高锰钢碳化物形态的热处理工艺。结果表明,水韧处理结合高压热处理和常压热处理可以有效地改善耐磨高锰钢组织中析出碳化物形态及分布,经水韧处理后再经5 GPa、650℃保温30 min的高压热处理和750～800℃保温60 min的热处理,耐磨高锰钢可获得弥散分布的颗粒状和短条状碳化物。