N80钢表面碳、氮、氧、铬共渗层的组织和耐腐蚀性能

采用低温气体多元共渗技术在N80钢表面制备了碳、氮、氧、铬共渗层,采用SEM、EDS等分析了渗层形貌、厚度及共渗元素的分布;采用XRD测定了共渗层的相组成;在饱和CO_2模拟油田介质中测试了共渗层的极化曲线与渗层的腐蚀速率。结果表明:渗层厚约70μm,由靠近基体含有大量Cr-O相约40μm厚的氧化物层、紧邻氧化物层含有ε、γ′相约15μm厚的氮化物层及最外层的铁氧化物层组成;碳、氮、氧、铬共渗层自腐蚀电位比基体正移320 mV,在饱和CO_2模拟油田介质中腐蚀速率仅为基体的1/3。     

防喷器材料多元共渗后的耐蚀性研究

低温气体多元共渗技术是一种新工艺，本文采用该工艺在防喷器材料表面同时渗入C，N，O三种元素，打破了传统的单一渗透，实现了在材料表面形成均匀的渗层，而且渗层又厚又致密。利用X射线衍射和扫描电子显微技术测定了渗层相的组成以及渗层的表面形貌，采用电化学测试技术对渗层在1．0mol／L稀HCl溶液中的耐蚀性与原始材料的耐蚀性进行了对比试验研究。结果表明，渗层以氧化物、氮化物和碳化物为主，且氮化物居多，渗层约30μm，耐蚀性能得到了大大的提高，相对原始材料的耐蚀性提高了3倍左右，其腐蚀速度也低于原始试样的腐蚀速度，这对钻井防喷器控制装置性能的提高有重要意义，具有广阔的应用前景。     

20钢多元共渗后的性能研究

采用低温气体多元共渗技术在20钢表面同时渗入C、N、O3种元素,在材料表面形成了厚且致密均匀的渗层。利用X射线衍射和扫描电子显微技术测定了渗层相的组成以及渗层的表面形貌,采用摩擦磨损实验和电化学测试技术对渗层和原始材料的耐磨性进行了对比试验研究。结果表明渗层以氧化物、氮化物和碳化物为主,且氮化物居多,相对于原始材料,硬度、耐蚀性提高,摩擦因数降低,这在工业生产中有广阔的应用前景。     

0Cr18Ni9Ti不锈钢表面渗锆合金层的耐腐蚀性能及抗高温氧化性能

采用双辉等离子渗金属技术在0Cr18Ni9Ti奥氏体不锈钢表面制备渗锆合金层,然后将其分别置于在0.5mol·L-1 HCl溶液、3.5%NaCl溶液、0.5mol·L-1 NaOH溶液中进行电化学腐蚀试验,另在静态空气中进行了1 000~1 150℃的高温氧化试验,研究了渗锆合金层的耐腐蚀性能及抗高温氧化性能,并与不锈钢基体进行了对比。结果表明:在三种溶液中,不锈钢基体的相对腐蚀速率分别为渗锆合金层的24.43倍、2.44倍、1.90倍,不锈钢基体表面发生了较为严重的腐蚀,而渗锆合金层只出现了局部腐蚀坑,这是因为在腐蚀过程中其表面形成了一层致密的ZrO2钝化膜;不锈钢基体和渗锆合金层的氧化质量增加曲线都基本遵从抛物线规律;在1 150℃氧化20h后,不锈钢基体表面氧化严重,而渗锆合金层的表面形貌较好,存在少量孔洞,组织相对致密。     

纯钛表面渗钽改性层在硫酸中的耐腐蚀性能

为了提高纯钛在强酸中的耐蚀性能,采用双层辉光等离子渗金属技术对纯钛表面渗钽;使用电化学扫描法和失重法对比研究了钽改性层及纯钛基体在硫酸中的耐腐蚀性能,并通过扫描电镜观察其腐蚀形貌。结果表明:改性层厚约15μm,由沉积层和扩散层组成,与基体形成了冶金结合,钽呈梯度分布;在质量分数10%和40%硫酸中,钽改性层年腐蚀速率分别只有纯钛的30%和1.2%,在75%硫酸中改性层年腐蚀速率依然很小,只有0.008 8 mm·a~(-1);纯钛基体在浓硫酸中腐蚀120 h后,腐蚀表面已出现许多腐蚀坑,而钽改性层腐蚀前后的试样表面没有明显变化,整个改性层依然完整致密。     

新型合金工具钢软氮化渗层组织结构的研究

采用光学显微镜及X射线衍射仪分析了一种新型合金工具钢软氮化渗层的组织形貌和相结构,并与传统的高速钢进行比较。结果表明,该钢经过560℃×3h软氮化后渗层显微组织是由γ′和合金氮化物及碳化物组成的扩散层,未见连续的ε相形成。与传统高速钢比较,在相同工艺条件下渗速较快,渗层较深,脉状氮化物级别较低,渗层具有良好的综合性能。     

40Cr气体多元共渗后耐磨性研究

为了提高上述零件的耐磨性,延长使用寿命,对40Cr钢进行气体多元共渗处理。对渗层的相结构与形貌进行X射线衍射和扫描电镜分析,表明材料表面形成了由ε相组成的白亮层和由氮化物组成的扩散层,氮化物和渗层中存在的硬度很高的碳化物提高了材料的表面硬度。对气体多元共渗后的40Cr进行摩擦磨损试验,表明处理后40Cr的表面摩擦因数较处理前显著减小,其耐磨性得到较大提高,并随温度提高而更加显著。     

40Cr气体多元共渗后表面硬度研究

40Cr进行气体多元共渗处理后能形成渗层，通过X射线衍射和扫描电镜对渗层的相结构与形貌进行分析，在材料表面形成了由ε相组成的白亮层和由氮化物组成的扩散层，因此材料表面硬度增加并随着与表面距离的增加而呈梯度减小。     

Q235钢表面低温气体N,C,O多元共渗的研究

利用自行研制的一种新型智能化低温气体多元共渗技术，在碳素结构钢Q235表面进行低温气体C，N，O多元共渗。经N，C，O多元共渗的Q235钢表面形成均匀渗层，渗层由钝化层、白亮层和过渡层组成，厚度约为100μm。Q235钢表面显微硬度显著提高，达到HV685。利用SEM对共渗层进行了成分分析，最外层钝化层中氧含量显著高于基体；渗层中白亮层氮元素的含量明显提高，在试样表面形成氮化物，从而大大提高了Q235钢的表面硬度；过渡层中碳元素的含量最高。     

汽车零件表面改性的QPQ复合表面处理技术研究

研究了汽车零件常用材料SUM24和SUH38经QPQ盐浴复合氮化处理后渗层结构和表面性能.结果表明,QPQ处理后氮化层组织由外向内依次为氧化膜层、化合物层和扩散层.随着基体中Cr、Mo强氮化物形成元素增多,化合物层厚度增加,扩散层尺寸减小.QPQ处理后工件表面耐腐蚀性、硬度和变形量均优于相同条件下常规液体氮化处理.     

Small-scale structural and mechanical characterization of the nitrided layer in martensitic steel

Pulsed Plasma Nitriding (PPN) of high-strength low-alloy steels used for offshore applications is a promising approach for controlling erosion, corrosion and hydrogen embrittlement under service conditions. In this work, the microstructure, composition and hardness of the nitride layer produced by an optimized PPN process on 2.25Cr–1Mo steel were examined. The nanomechanical properties of the nitride layer were investigated via nanoindentation along the depth of the nitride layer to understand the interconnected effect of the existing microstructure with the one developed after the nitriding process and the nitrogen concentration. The results showed that the nitride layer is composed of a compound layer and diffusion layer with hardness four times higher than the untreated material, which gradually decreases across the diffusion layer.     

高压大流量直轴式柱塞泵缸体的设计与研究

讲述了用球墨铸铁替代传统复合结构材料设计高压柱塞泵缸体。通过对K3V112高压大流量柱塞泵的计算,验证了球铁作为缸体材料的可行性。对球铁进行气体软氮化可以得到具有良好的耐磨性、耐腐蚀性、耐热性和耐热粘附性的氮化物层,大大提高了缸体的性能。通过材料替代,简化了缸体的制造工艺,大大降低了制造成本并提高了生产效率与成品率。     

Electrochemical corrosion property of nanostructure layer of Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy

Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy was nanocrystallized with supersonic fine particles bombarding (SFPB). The microstructure features of nanocrystalline layer were determined by XRD, TEM, and microhardness tester. The electrochemical corrosion properties of the surface of original sample and the nanocrystallized sample surface were tested by CHI660 tester. That random crystallographic oriented particles (average grain size of 16 nm) were observed in the top surface layer of Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy, which could be attributed to the surface nanocrystallization. The electrochemical corrosion results show that the impedance of the sample nanolayer is reduced after SFPB with 30 min, and the corrosion resistance is lower than the original sample. The residual internal stress from the process of SFPB is one of the main factors to decrease the nanolayer corrosion resistance of Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy. However, the corrosion resistance is significantly recovered after stress relief annealing with 250–350 °C.     

W4Mo3Cr4V高速钢稀土多元共渗层的性能

利用稀土多元共渗工艺将碳、氮、氧、硫、硼、稀土元素同时渗入W4Mo3Cr4V高速钢表面,研究了多元共渗层的硬度、耐磨性能及表面残余应力等。结果表明:多元共渗层由化合物层(主要为氧化物、硫化物和碳化物)和扩散层组成;共渗层显微硬度最高达1 150 HV左右;多元共渗层较钢表面的摩擦因数大幅降低,耐磨性能提高,其表面产生了较高的残余压应力,有利于提高材料的疲劳性能。     

Laboratory assessment of wear on nitrided surfaces of dies for hot extrusion of aluminium

A newly designed “block-on-cylinder” wear resistance testing rig, which allows testing at higher contact pressures than conventional testing methods, was used to elucidate the effect of an iron nitride compound layer (white layer) on the wear resistance of nitrided dies used for hot extrusion of aluminium (Al). The tested dies (AISI H13) with various nitrided microstructures were provided by different manufacturers of equipment for plasma and gas nitriding. The wear surfaces were analysed by SEM, BEC, micrography and roughness measurements. It was found that the iron nitride compound layer is chemically more stable against hot Al in comparison to die material. Deterioration of the compound layer begins with cracking, and as a consequence, its spalling from the nitrided surface. A high thickness of the compound layer combined with a low nitriding depth leads to its earlier spalling and vice versa. Due to the increased roughness at the removal sites, accelerated chemical attack by hot Al takes place. Comparative and simultaneous testing of two nitrided samples was carried out.     

Effect of electro discharge machining (EDM) on the AISI316L SS white layer microstructure and corrosion resistance

The localised corrosion resistance of austenitic stainless steels is strongly influenced by the quality of finished surface. EDM machining induces substantial changes by the high thermal gradients generated by electric sparks. Experimental techniques such as roughness measurement, scanning electron microscopy (SEM), energy dispersive microanalysis (EDX) and X-ray diffraction technique, reveal micro-geometrical, microstructural, chemical and mechanical changes. These changes lead to white and heat-affected layers with a depth less than 100 μm. The white layer is a melted material characterised by dendritic structure and constituted by austenite, chromium carbide and ε-carbide. The heat-affected layer is characterised by very large grain size comparatively to the bulk material. Electrochemical test coupled with metallographic examinations using SEM reveals a weakening of the resistance to pitting and intergranular corrosion comparatively to diamond polished surface. This weakening is correlated to differences in structure and chemical composition of white layer. Susceptibility to stress corrosion cracking has been attributed to the field of tensile residual stresses resulting from thermal effects. The removal of the white layer material by polishing or wire brushing restores the corrosion resistance of the AISI316L SS.     

加弧辉光渗Ti在石墨电极上的应用

介绍了一种新的表面合金化技术－－加弧辉光离子渗钛技术。利用该技术可在石墨板上形成均匀的渗钛层。试样在0．5mol/LH2SO4溶液中进行电化学腐蚀测试，结果表明：渗钛石墨电极比石墨电极的耐蚀性有很大提高，与钛板的抗腐蚀性能相当。探讨了渗层钛浓度分布，并用X射线衍射对渗层相组成进行了分析。