高铬铸铁变温马氏体相变与摩擦诱发马氏体相变关系的研究

对三种含Mn、Si、Mo亚共晶高铬铸铁的变温马氏体相变进行了DSC分析,并对表层的摩擦诱发马氏体做了X射线衍射分析。结果表明,变温马氏体相变前期,马氏体形核、长大阻力较大。在M_s温度相近的情况下,变温马氏体相变形核、长大速率快的,其摩擦诱发马氏体量也多。     

High temperature oxidation of a (Cr2N−Mo2S3)/Cr double-layered coating deposited on steel by D.C. magnetron sputtering

A coating consisting of (Cr₂N−Mo₂S₃) overlay coating and an underlying Cr coating was deposited on a steel substrate by D.C. magnetron sputtering. The oxidation characteristics of the deposited double-layered coating were studied at temperatures ranging from 400 to 900 °C in air. The oxidation product was primarily Cr₂O₃. The unreacted coating beneath the oxide scale had some dissolved oxygen, sulfur, and iron. Oxidation of the coating occurred via complex routes such as the outward diffusion of chromium and nitrogen from Cr₂N and iron from the substrate, and the inward transport of oxygen from air, chromium from Cr₂N, and S from Mo₂S₃. This counter diffusion of various ions occurred easily via fine crystallites that constituted the coating, which had some solubility of S, O, and Fe.     

Chromium-nitride in situ composites with a compositional gradient formed by reactive DC plasma spraying

Nitrides of transition metals have good wear- and corrosion-resistant properties because of their high hardness and chemical stability. Chromium-nitride coatings can be deposited by ion plating; however, the thin thickness due to the slow deposition rate must be improved for severe wear-resistant applications. The main objective in this paper is to realize good structural control in the processing of chromiumnitride in situ composite coatings formed at a high deposition rate. They were synthesized by reactive low-pressure plasma spraying using elemental chromium powder as a spray material. The transferred arc between the gun electrode and the substrate was used to accelerate the nitriding reaction. The sprayed coatings consist of chromium, Cr₂N, and CrN, which have a composition gradient from the substrate interface to the surface. The volume fraction of Cr₂N increases with transferred arc current, and nonreacted chromium concurrently decreases, except close to the substrate. The CrN phase, however, only exists as a surface layer of 20 to 30 μm because it is decomposed to Cr₂N above 1420 K. The hardness of the composite coatings depends on the volume fraction of Cr₂N, and it increases to 1300 HV at a Cr₂N volume fraction of 0.98. The seizure stress with lubricant depends on the coating hardness. The maximum seizure stress of 24.9 MPa is obtained at a hardness of 1300 HV. The composite coatings also show a superior wear resistance. Hence, the Cr₂N in situ composite coatings synthesized by reactive plasma spraying with transferred arc are expected to be good candidates for wear-resistant applications.     

高Si/C值在低铬耐热铸铁阀体上的应用

提高低铬耐热铸铁化学成份中的Si/C值 ,在稳定获得较高强度的同时降低了铸铁的残余应力 ,提高了强度 /应力比 ,具有较强的抗裂纹能力有效防止了矩形阀体的裂纹。分析了Si对提高铸铁耐高温性能的良好效果 ,增加Si量可适当的提高含铬量。     

热处理对铬青铜组织和性能的影响

研究了均匀化处理、固溶时效、冷变形时效等对铬青铜显微组织和性能的影响.结果表明均匀化处理可有效改善铬在铜基体中的分布;铬青铜的最佳固溶工艺为1000℃保温1 h后水淬;较好的时效工艺为470℃×4 h,此时合金的硬度和电导率分别为121.5 HV和79.8%IACS.时效前经适当的冷变形,其硬度为146.7 HV,电导率为85%IACS,和未冷变形直接时效相比分别提高了25.2 HV和5.2%IACS.     

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.     

铌和热处理对高铬铸铁组织性能的影响

在无钼高铬铸铁中加入适量铌和锰,研究了热处理工艺对其组织和性能的影响。结果表明:加铌并配合高温淬火-亚临界回火工艺,可改善共晶碳化物的形态和分布,并产生明显的二次硬化。试验合金的宏观硬度与Cr15Mo1Cu1高铬铸铁相当,而抗磨性优于后者。     

氮对高纯奥氏体不锈钢耐晶间腐蚀性能的影响

采用电化学、化学浸渍、俄歇电子能谱分析、物理化学相分析等方法研究了氮对高纯奥氏体不锈钢000Cr19Ni14耐敏化态晶间腐蚀和非敏化态晶间腐蚀性能的影响,并探讨了其作用机理.结果显示,高纯奥氏体不锈钢加氮合金化(≤0.20%)基本上消除敏化态晶间腐蚀,敏化处理不会引起晶界贫铬;当氮含量不超过0.087%时,对非敏化态晶间腐蚀影响很小,而超过0.087%时,由于在晶界氮元素的偏聚以及氮化铬的析出加速非敏化态晶间腐蚀.     

热处理对D618堆焊层组织和性能的影响

研究了高碳高铬铸铁型硬质合金堆焊层在不同热处理条件下的组织、硬度与耐磨性。研究结果表明D618硬质合金堆焊层经850℃加热后空冷或850℃加热后油冷＋400℃回火，具有较高的硬度和优异的耐磨蚀磨损性能，比35CrMo低合金钢碳氮共渗（850℃油冷＋200℃回火）后的耐腐蚀磨损性能提高3－12倍。     

新型高铬铸铁自保护堆焊药芯焊丝

研究了一种新型高铬铸铁堆焊药芯焊丝，分析了焊丝的脱渣性、抗裂性、耐磨性、硬度和金相组织。实验结果表明，该焊丝采用普通埋弧焊机，不需加入任何保护气体和焊剂能顺利进行堆焊，简化了操作过程，综合成本低；脱渣性好、熔敷速度快；不预热时连续堆焊也不出现裂纹，抗裂性良好；单道单层堆焊后室温硬度为48HRC左右，切削加工性能好；耐磨性为某硬度基本相同的高铬铸铁药芯焊丝耐磨性的1．27倍。