Papers by Keyword: 40Cr Steel

Abstract: External grind-hardening is a new technology combing grinding and quenching. Hardening tests are carried out according to 3-level and 3-factor orthogonal method for 40Cr steel, and metallographic observation and hardness measurement are put forward. Martensite is found in the surface layer structure, which hardness reaches HV647.4~719.4 and depth is about 0.22~1.1mm. The practicability of the new technology is confirmed. Orthogonal analysis is proceeded successively for the acquirements of influencing pattern and significance of factors based on the hardening results.

Abstract: The paper presents a failure analysis of tower axle in the water tank wire drawing machine. Material of the tower axle is 40Cr steel. In order to analyze the failure reasons of tower axle in the water tank wire drawing machine, we take experimental means such as morphological analysis, mechanical property testing, micro-metallography and scanning electron microscopy (SEM) of fracture observation, etc. The results show that the fracture of tower axle belongs to brittle fracture. The content of inclusions is more, and the composition is complex in the material. The heat treatment technology is improper. Improper quenched and tempered processing technologies cause more reticular and blocky ferrite in the steel. These are the main reasons for fracture of the tower axle.

Abstract: Individual corrosion and galvanic corrosion behaviors of depleted uranium (DU) and 40Cr steel were investigated by electrochemical analyzing technologies in 3.5w.t%NaCl solution, including open circuit potential(OCP) test, linear polarization(LP) test, potentiodynamic polarizaition(PD) test, galvanic corrosion potential and corrosion current density test. The results reveal that the OCP of DU and 40Cr steel are around -790mV and -660mV, respectively. 40Cr has a higher linear polarization resistance than DU in galvanic corrosion. The dynamic processes of galvanic corrosion goes through an conversion in the whole test period. DU acts as anode with an accelerated corrosion rate, while the 40Cr steel behaves as cathode during the process of galvanic corrosion for DU/40Cr couple. The galvanic potential and current density of the DU/40Cr couple are -780mV and 17.5μA/cm-2, respectively.

Abstract: Machined residual stress is an important index in machining quality, and pre-stress cutting is a process which can increase the residual compressive stress on machined surfaces. This paper investigated the effect of machining parameters and pre-stress on residual stress of 40Cr steel by orthogonal experiment. The experiment results also showed that pre-stress could increase the residual compressive stress effectively, and it had obvious significance for residual stress than those significances of machining parameters; ap had more obvious affect on the residual stress than vc and f have, and residual compressive stress decreased with the increase of ap, vc and f. A prediction formula for residual stress of pre-stress hard turning was obtained from the experiment results and it was verified reliable by other experiment.

Abstract: TiC-based ceramic cutting tools with three different particle size levels of Al₂O₃ additives were fabricated and tested. Theses tool materials were identified as TA, TA10A5 and TA30A5 respectively in this study. Another commercial cutting material identified as LT55 was used in this study as baseline to investigate cutting performance by comparing the flank wear size. The experimental results showed that multi-scale nanocomposite ceramic tool TA10A5 had much better wear resistance than the other tools when turning at a lower speed. The wear mechanisms were mainly adhesive wear in the rake face. While cutting at a higher speed, the breakage failure occurred for the tools TA10A5 and TA30A5.

Abstract: The influence of gas nitriding on the wear and corrosion resistance of 40Cr steel was investigated. Gas nitriding experiments were carried out at 550°C for 2h and 10h. The microstructure and hardness gradient were observed and analyzed through metallurgical microscope and micro hardness tester. The polarization curves were scanned by the M398 Corrosion Integrated Test System. Using MG-200 high speed friction and wear testing machine did end mill test and calculated the wear rate. By scanning electron microscopy (SEM) observationing the worn surface morphologies. The results show that after different nitriding time, the specimen surface forms with nitrided layer of different thickness, and changes with the hardness decreased with the penetration depth. Furthermore, the gas nitriding treatment may change the corrosion potential positively and reduce the density of the electric current of 40Cr steel. In addition, wear mechanism of the matrix is mainly adhesive wear, but after nitriding is mainly abrasive wear. The wear rate reduces significantly.

Abstract: To increase the mechanical properties of the metal rollers, Mo and Mo+Y₂O₃ alloy powders were designed. And a kind of coating fabricated by a continuous wave CO₂ laser surface alloying(LSA) on 40Cr steel roller was obtained. The effect of Mo and Mo+Y₂O₃ on microstructure, hardness and wearing resistance of alloying coating were studied by OM, SEM, XRD, microhardness tester and wearing tester. The experimental results indicate that the grain size in alloying coating is obviously fined, and the grain boundary is strengthened. The uniformity and density of microstructure are improved. The microhardness and wear resistance of alloying coating are significantly increased.

Abstract: The main purpose of this paper is to research on the different ion nitriding temperatures of 40Cr effect on the surface hardness, wear resistance of the workpiece. With series of experiment and test of micro-hardness, ring-block wear, metallographic observation, to select the optimization temperature for the ion nitriding process of 40Cr steel.

Abstract: In this paper, 40Cr steel was gas-nitrided for varying time. The microstructure and microhardness of the nitrided layer were examined by means of optical microscope and microhardness tester. The CO₂ corrosion behavior of 40Cr steel influenced by nitriding was studied using high temperature high pressure autoclave. The SEM, EDS and XRD technique were adopted to study the characteristics of CO₂ corrosion scales on 40Cr steel. The results show that the pitting is generated for all the un-nitrided and nitrided specimens, however, the corrosion tendency and corrosion rate decreases with nitriding time increasing, mainly due to the compact of FeCO₃ formed on the surface.

Abstract: A nanostructured layer can be introduced on the surface of metallic materials by surface severe plastic deformation. A surface severe plastic deformation method-Supersonic Particles Bombarding (SSPB) was used to treat the anealled 40Cr steel. The surface and cross sectional microstructure of 40Cr steel after SSPB treatment were characterized by means of X-ray diffraction, optical microscopy and transmission electron microscopy equipped with a Kikuchi line program to determine the grain orientations. Equiaxed nanocrystallites with random crystallographic orientation were obtained on the top surface of 40Cr steel after SSPB treatment. The surface microstructure was composed of nanostructure area, deformed area and matrix. Geometrically necessary boundaries and incidental dislocation boundaries were formed in the deformed ferrite at the distance to the surface of about 50-60μm, and the original coarse ferrite grain was divided into lamaller structure.