AS41耐热镁合金的摩擦学行为研究

本文研究了AS41耐热镁合金在室温和200℃时的显微组织、力学和摩擦学性能,并探讨了其在高温的摩擦学机理。研究表明:AS41耐热镁合金主要由基体(α-Mg)相和第二相(Mg17Al12、Mg2Si和MgO相)组成,其在200℃时除延伸率有所增加外,抗拉强度和屈服强度均较室温时显著下降。耐热镁合金的摩擦系数随载荷增大而减小,滑行速度和滑行距离对摩擦系数的影响不大;磨损率随着载荷和滑行距离的增加而增大,但随滑行速度的增加而减小;且耐热镁合金在200℃的摩擦学性能优于其室温摩擦学性能。随着载荷变化,磨损机理发生变化;低载荷时表现为氧化磨损和磨粒磨损;中等载荷时表现为磨粒磨损和轻微剥层磨损;较高载荷时表现为剥层磨损。     

M50钢高应力高温摩擦磨损行为与微观机制

利用SRV-4摩擦磨损试验机对M50轴承钢进行了滑动摩擦试验，通过改变试验环境温度与加载应力探究了M50钢的高温摩擦磨损性能。采用激光共聚焦显微镜(LSCM)、扫描电子显微镜(SEM)和能谱仪(EDS)观察高温高应力下磨损对钢的影响。研究发现，试验环境温度200℃与210 MPa以上摩擦剪力的共同作用下，大尺寸MC型碳化物表层基体粘着剥落，MC型碳化物破碎、迁移，加剧磨损。试验环境温度200℃粘着磨损加剧且磨损面形成的(Cr, Fe)₂O₃氧化膜厚度不足导致粘着磨损量达到最大值。试验环境温度升高至315℃,氧化膜趋于连续且膜厚增加，粘着磨损减弱，接触应力2.05 GPa时摩擦因数相较于室温下降27%。     

CSiMnCrVNb细晶钢的组织与性能

对于微合金化的碳的质量分数为0.15%～0.35%的CSiMnCrVNb合金钢,通过控制锻造比获得11～12级奥氏体原始晶粒.研究了试验钢的磨擦磨损行为,结果表明:于摩擦磨损条件下,碳含量较低的试验钢随载荷及磨损速度的增加,其磨损形式逐渐由显微切削转变为严重的粘着磨损并伴有疲劳剥落现象;碳含量较高的试验钢随载荷和磨损速度的增加,其磨损形式仍以显微切削为主,但犟沟变宽、加深,并伴有轻度粘着磨损及疲劳剥落现象.在动载冲击磨损条件下,其磨损形式以磨料磨损为主.碳的质量分数为0.35%的试验钢具有较好的组织、综合力学性能,在磨损过程中既可以抵抗石英砂磨粒的切削,又可以减少表面金属的剥落,表现出较佳的耐磨性.     

H13钢激光涂覆层的高温磨损性能

选取H13钢进行激光涂覆,获得激光熔覆涂层,并进行了微观组织和硬度的分析。采用销—盘式高温磨损试验机研究了H13钢涂层的高温磨损行为,并与H13钢进行对比。采用SEM、XRD、EDS等微观分析手段对H13钢和涂层磨面进行形貌、物相和成分分析,并探讨磨损机制。结果表明:在同一载荷条件下,当温度从400℃升至600℃时,涂层的磨损失重明显低于H13钢;当温度为600℃,载荷为150 N时,H13钢的磨损失重要更加严重,磨损表面发生了塑性挤出,磨损失重增加,而涂层的磨损失重要比H13钢小得多,说明涂层在高温情况下表现出良好的耐磨性。在同一温度下,涂层和H13钢的磨损失重都随着载荷的增加而增加。400℃,50 N时,H13钢和涂层的磨损机理为轻微磨损;400℃,150 N时,H13钢的磨损机理为氧化磨损,而涂层的磨损机理为轻微磨损;但是,在600℃,50 N时,H13钢的磨损机理为氧化磨损,涂层的磨损机理则是磨粒磨损;600℃,150 N时,H13钢的磨损机理为塑性变形,涂层的磨损机理则为磨粒磨损。     

滑液温度对Ti6Al7Nb合金的耐磨性能影响研究

利用RTEC摩擦磨损试验机开展Ti6Al7Nb合金的摩擦学试验,重点探讨滑液温度对其耐磨性能的影响。结果表明,滑液温度与Ti6Al7Nb合金的耐磨性能呈明显的正相关关系。随着滑液温度上升,Ti6Al7Nb合金的质量磨损量及平均摩擦系数均逐渐增大,滑液温度在46℃时蛋白质沉淀的析出会影响合金的磨损机理,导致质量磨损量较37℃时增加了一倍;扫描电子显微镜(SEM)分析发现,滑液温度为10、20、37℃时,磨损边缘区域受摩擦热作用影响,磨损机理主要为接触疲劳磨损、磨粒磨损及粘着磨损,磨损中心区未发现明显的粘着磨损特征,滑液温度为46、60℃时,边缘处磨损机理以接触疲劳磨损、磨粒磨损及粘着磨损为主,中心区磨粒磨损特征不明显,以粘着磨损为主。     

3Cr3Mo2V铸钢和3Cr13钢磨损行为的研究

采用销盘式磨损试验机对3Cr3Mo2V铸钢和3Cr13钢在环境温度25℃和200℃下进行干滑动磨损试验,研究了显微组织和摩擦氧化物对3Cr3Mo2V铸钢和3Cr13钢磨损行为的影响,并探讨其磨损机制。结果表明:摩擦氧化物对25℃和200℃下的磨损行为和磨损机制有显著的影响,而摩擦氧化物的减磨作用取决于其数量和基体状态等,与钢的成分和显微组织密切相关。高的铬含量阻碍摩擦氧化物的形成,低硬度的回火索氏体加速氧化物剥落,故无摩擦氧化物的作用或作用降低。     

半固态法制备A390高硅铝合金干摩擦磨损性能研究

采用传统铸造技术和半固态过流冷却技术分别制备了A390铝合金铸棒。在MVF-1A摩擦磨损试验机上研究了显微组织、外加载荷和温度对A390铝合金干滑动摩擦磨损性能的影响,对磨环材料为45^#钢。采用SEM对A390铝合金磨损面形貌进行了分析。结果表明：相同载荷和温度下,经半固态处理的A390铝合金材料耐磨性能更优异。随着外加载荷的增加,A390的摩擦系数和磨损率呈现先降低和增加的趋势;载荷为80 N时,A390的摩擦系数最稳定,磨损率最小。A390的摩擦系数和磨损率对温度变化较敏感,在100℃以下,磨损率变化较小,以磨粒磨损机制为主;当温度超过100℃时,摩擦系数波动明显,磨损面塑性变形严重,此时同时发生磨粒磨损和粘着磨损。     

钛合金与钢的干滑动磨损行为对比

采用高温磨损试验机对TC11合金和H13钢进行了各种温度和载荷下的磨损试验,对比研究了它们的磨损行为。研究发现,随温度和载荷的变化,TC11合金和H13钢表现出完全不同的磨损行为。随着温度升高,TC11合金的磨损率在200℃时增加,然后大幅度降低,在400~600℃达到最低值。而H13钢的磨损率先降低,在200℃达到最低值,随后显著增加,在400~600℃出现从轻微至严重磨损的转变。其行为差异是由于氧化物的保护作用和两种材料热软化抗力的不同而引起的。     

不同环境温度下典型身管用钢磨损性能研究

通过摩擦磨损、高温硬度及相应的分析试验研究了典型身管用钢32Cr2MoVA、30SiMn2MoVA在室温、200、400以及600℃下的摩擦磨损行为与规律.结果表明:两种材料的摩擦系数在各个温度区间内的区别不大,主要受摩擦氧化物产生与否影响.32Cr2MoVA的磨损率随着温度的提高先降低再提高之后又下降,30SiMn2MoVA的磨损率随着温度的上升而先降低,然后逐渐升高,600℃达到最高.温度、身管钢在高温下的硬度和磨盘材料与滑动销的高温硬度差(H_d-H_p)共同影响磨损表面氧化物层的最终形态.室温至200℃时,身管钢磨损行为主要受表面氧化物层的影响.室温下两种身管钢磨损机理均为黏着磨损及磨粒磨损,200℃时均为氧化轻微磨损.环境温度达到400℃以上时,身管钢以及磨盘材料的基体硬度开始影响磨损行为.400℃时两种身管钢磨损机理均为氧化严重磨损.600℃时,32Cr2MoVA的H_d-H_p减小,磨损表面出现了厚度很大、致密的氧化物层,磨损机理为氧化轻微磨损;而30SiMn2MoVA的H_d-H_p显著增大,试样发生了明显的塑性挤出,为塑性挤出磨损.      

塑料模具钢NAK80和S136的耐磨性能对比研究

以预硬化塑料模具钢NAK80和S136为研究对象,对比研究了两者的显微硬度、金相组织以及不同载荷下的摩擦磨损行为。结果表明:NAK80钢金相组织为板条状马氏体和粒状贝氏体,S136钢的金相组织为铁素体基体和细小碳化物,显微硬度(HV)分别为405.01±10.63和354.21±6.14。NAK80和S136钢的摩擦系数均随着载荷的增加而降低,在60 N时,两者都达到各自最低的摩擦系数(0.34和0.37),当载荷增加至80 N,摩擦系数反而上升。整体而言,S136的摩擦系数高于NAK80。不同载荷条件下,NAK80的磨损行为具有高的载荷敏感性;而S136具有更加稳定的耐磨性。低载荷时,以磨粒磨损和剥层磨损为主,NAK80耐磨性优于S136;高载荷时,以粘着磨损和磨粒磨损为主,S136钢耐磨性优于NAK80。     

Effects of the Ambient Temperature and Load on the Wear Performances and Mechanisms of H13 Steel

The dry sliding wear tests of H13 steel were performed under atmospheric conditions under various ambient temperatures and loads; the wear performances and the wear mechanisms were studied. At room temperature (RT), the wear loss of the steel gradually increased with increasing the load. An adhesive wear prevailed with little tribo-oxides on the worn surfaces. Under the atmospheric conditions at 473 K (200 °C) and a load of 100 N or above, a mild oxidation wear prevailed with about 20-μm thickness of tribo-oxide layer forming on the asperities of worn surfaces. The wear loss first reduced and then slightly increased with increasing the load. Compared with the other ambient temperatures, the wear at 473 K (200 °C) retained the lowest wear loss due to the protection of the tribo-oxide layer. As the ambient temperature reached 673 K (400 °C), the wear loss increased with increasing load, leading to higher wear than those observed at RT and at 473 K (200 °C). The predominant wear mechanism at 673 K (400 °C) was oxidation wear, unlike mild oxidation wear, which dominated at 473 K (200 °C).     

Wear Behavior and Mechanism of a Cr-Mo-V Cast Hot-Working Die Steel

The wear behavior and mechanisms of a Cr-Mo-V cast hot-working die steel with three microstructures (tempered martensite, troostite, and sorbite) were studied systematically through the dry-sliding wear tests within a normal load range of 50 to 300 N and an ambient temperature range of 298 K to 673 K (25 °C to 400 °C) by a pin-on-disk high-temperature wear machine. Five different mechanisms were observed in the experiments, namely adhesive, abrasive, mild oxidative, oxidative, and extrusive wear; one or more of those mechanisms would be dominant within particular ranges of load and temperature. The transition of wear mechanisms depended on the formation of tribo-oxides, which was related closely to load and temperature, and their delamination, which was mainly influenced by the matrix. By increasing the load and ambient temperature, the protective effect of tribo-oxides first strengthened, then decreased, and in some cases disappeared. Under a load ranging 50 to 300 N at 298 K (25 °C) and a load of 50 N at 473 K (200 °C), adhesive wear was the dominant wear mechanism, and abrasive wear appeared simultaneously. The wear was of mild oxidative type under a load ranging 100 to 300 N at 473 K (200 °C) and a load ranging 50 to 150 N at 673 K (400 °C) for tempered martensite and tempered troostite as well as under a load of 100 N at 473 K (200 °C) and a load ranging 50 to 100 N at 673 K (400 °C) for tempered sorbite. At the load of 200 N or greater, or the temperatures above 673 K (400 °C), oxidative wear (beyond mild oxidative wear) prevailed. When the highest load of 300 N at 673 K (400 °C) was applied, extrusive wear started to dominate for the tempered sorbite.     

Selection of Heat Treatment Process and Wear Mechanism of High Wear Resistant Cast Hot-Forging Die Steel

 Dry sliding wear tests of a Cr-Mo-V cast hot-forging die steel was carried out within a load range of 50-300 N at 400 ℃ by a pin-on-disc high-temperature wear machine. The effect of heat treatment process on wear resistance was systematically studied in order to select heat treatment processes of the steel with high wear resistance. The morphology, structure and composition were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS); wear mechanism was also discussed. Tribo-oxide layer was found to form on worn surfaces to reduce wear under low loads, but appear inside the matrix to increase wear under high loads. The tribo-oxides were mainly consisted of Fe3O4 and Fe2O3, FeO only appeared under a high load. Oxidative mild wear, transition of mild-severe wear in oxidative wear and extrusive wear took turns to operate with increasing the load. The wear resistance strongly depended on the selection of heat treatment processes or microstructures. It was found that bainite presented a better wear resistance than martensite plus bainite duplex structure, martensite structure was of the poorest wear resistance. The wear resistance increased with increasing austenizing temperature in the range of 920 to 1120 ℃, then decreased at up to 1220 ℃. As for tempering temperature and microstructure, the wear resistance increased in following order: 700 ℃ (tempered sorbite), 200 ℃ (tempered martensite), 440 to 650 ℃ (tempered troostite). An appropriate combination of hardness, toughness, microstructural thermal stability was required for a good wear resistance in high-temperature wear. The optimized heat treatment process was suggested for the cast hot-forging steel to be austenized at 1020 to 1120 ℃, quenched in oil, then tempered at 440 to 650 ℃ for 2 h.     

Wear Behavior and Mechanism of Spheroidal Graphite Cast Iron

Wear behavior and mechanism of spheroidal graphite cast iron were studied on a pin-on-disk elevated temperature wear tester. The phase and morphology of worn surfaces were examined by X-ray diffraction and scanning electron microscopy. Results show that with an increase of load, wear rate of spheroidal graphite cast iron gradually increases under low loads, rapidly increases or potentially increases under high loads; wear rate increases with increasing ambient temperature. At 25–200 °C, adhesive wear prevails; oxidative wear and adhesive wear coexist at 100 °C. As load surpasses 150 N at 100 °C, extrusive wear appears. The elevated-temperature wear of spheroidal graphite cast iron is a physical and chemical process including the following reactions: xFe + y/2O₂?Fe_xO_y, 2C + O₂?2CO and Fe_xOy + yCO?xFe+yCO₂. Hence, at 400 °C, the amount of graphite and tribo-oxides are substantially reduced because of reductive function of graphite. It can be suggested that wear-reduced effect of graphite and tribo-oxides is impaired.     

Effect of Microstructures on Resistance of a Hot Elevated-Temperature Wear Working Die Steel

 Elevated-temperature wear tests under atmospheric conditions at 400 ℃ were performed for a hot working die steel H21 on a pin-on-disk wear tester. The phase and morphology of worn surfaces were examined using XRD and SEM, and the relation of wear resistance to tempered microstructures was studied for H21 steel. XRD patterns exhibit that oxidative wear is a predominated wear mechanism with Fe3O4 and Fe2O3 on worn surfaces. It is found that with increasing normal load, obvious plastic deformation of substrate appears on worn surfaces. Microstructures start to affect apparently wear resistance of the steel with an increase of load. Under loads of 50-100 N, wear losses of steel retain low values and relatively approach for steels with various microstructures. As loads are increased to 150-200 N, wear losses of steel start to increase obviously and present apparent difference for steel with various microstructures. Wear resistance is found to increase in the sequence as follows: tempered sorbite, tempered martensite, tempered troostite without secondary hardening and tempered troostite with secondary hardening or upcoming one. Higher strength and microstructural stability are required for steels with excellent wear resistance.     

超音速火焰喷涂CoCrW涂层的磨损特性

采用超音速火焰喷涂工艺制备了cocrw涂层,利用金刚石锥体为摩擦副,通过往复式磨损试验机测试了涂层在室温和600℃时的磨损性能,分析了涂层的磨损机理。结果表明：在室温和600℃两种温度条件下,磨损量均随着载荷的增大而增加,而涂层在同一载荷作用下,室温和600℃两种温度下的磨损量较为接近。磨损形貌则表现为磨损初期呈现明显的犁削沟槽、小片状残留物、还有小凹坑;磨损较长时间后则显示明显的粘着磨损形貌和涂层颗粒脱落坑特征。     

新型耐高温磨损钢板组织性能与高温磨损行为研究

摘要：随着低合金耐磨钢应用领域逐渐增加,对其中高温条件下的耐磨性能提出了要求。通过成分设计、控制轧制和离线热处理工艺制备了一种Mo、V合金化新型低合金高温耐磨钢。初步探索了其在300~500℃温度范围的高温磨损行为和组织演变,并与同硬度级别的商用常规耐磨钢NM450进行了对比分析。结果表明：通过添加Mo和V等元素可以抑制位错密度降低、板条合并以及渗碳体析出、长大过程,提高了高温耐磨钢的高温强度等力学性能,从而提高了其高温磨损性能。300、400、500℃温度的磨损性能分别是常规NM450的1.5、1.4和2.2倍左右。300到500℃的磨损机制由磨料磨损向氧化磨损和塑性变形转变。高温耐磨钢高温屈服强度相对更高,塑性变形更小。     

Abrasive Wear Behavior and Mechanism of High Chromium Cast Iron

The abrasive wear behavior of high chromium cast iron(containing 12.9mass%chromium)austenitized at1 050 ℃for 2hand austempered in salt bath at 320℃for 4hwas evaluated.Abrasive wear was performed using alumina abrasive under four different loads,namely 50,100,150,and 200 N,for 36 000 cycles.The worn surfaces and wear debris were analyzed by scanning electron microscopy,laser confocal microscopy and X-ray diffraction.Microhardness profiles were also obtained in order to analyze the strain-hardening effects beneath the contact surfaces.Results indicate that the retained austenite in high chromium cast iron has experienced induced martensitic transformation after tests,for small amounts of retained austenite could be detected by X-ray diffraction.In addition,there is a close relationship between wear mechanism and test load.Under the condition of lower test load,the wear mechanism is an uninterrupted and repeated process,during which matrix is cut at first and then fine carbides flake off.As to higher test load,scratching and spalling induced by cleavage fracture of blocky carbide are the wear mechanism.