Effect of Deep Cryogenic Process on the Microstructure and Hardness and Wear Resistance of High Carbon Tool Steel

2018 ◽  
Vol 934 ◽  
pp. 100-104
Author(s):  
Yuan Ching Lin ◽  
Ji Wei Gong

In this investigation, the effects of different heat treatment conditions on the mechanical properties of high carbon tool steel (SK2) were explored. Experimental results indicated that immediately doing deep cryogenic treatment can effectively reduce retained austenite after quenching. The moment of the holding time for the cryogenic treatment was extended can promote the fine carbides precipitated, and thus increased its hardness. The results of X-ray diffraction showed that the carbides in the matrix included Fe3C and Fe7C3.The wear test results demonstrated that the specimen with Q-T1hr-C24hr-T1hr treatment has the highest wear resistance than the others, which was caused by the effect of several tempering processes to improve toughness of the matrix and to precipitate considerable quantities of the fine carbides.

2013 ◽  
Vol 12 (1) ◽  
pp. 25
Author(s):  
A. F. Hernandez ◽  
C. R. M. Silva ◽  
J. A. Araujo ◽  
J. D. B. De Mello

The Deep Cryogenic Treatment (DCT) has been used for improvement of steel mechanical properties, basically the abrasive wear resistance. At this work the cryogenic treatment at -190oC for 20 hours was applied, after conventional heat treatment, to improve its abrasive wear resistance. The specimens, divided in two groups, had been austenitized for forty five minutes at 965oC and 1065oC, respectively, then quenched in oil at room temperature. Afterwards they were tempered at 565oC for 90 minutes, and then cooled in air. Subsequently some samples were treated cryogenically, and some of them were submitted to a new cycle of tempering at 565oC for 90 minutes. The performed experiment included: hardness brinell, Xraydifratometry, metallography and micro-abrasive wear test. Variations in the microstructure with an improvement in the abrasive wear coefficient were found. These variations are probably a positive effect of the DCT on the samples microstructure. The microstructure were transformed from blocks of parallel lath martensite to small parallel or almost parallel packages of fine needles forming austenite. Traces of previous or retained austenite were found delimiting the grains. It is presumed that micro-carbide homogeneously distributed in the matrix and in the grain´s contours of the retained austenite was formed.


Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 808 ◽  
Author(s):  
Binzhou Li ◽  
Changsheng Li ◽  
Yu Wang ◽  
Xin Jin

This paper investigated the response of carburized 20CrNi2MoV steel to cryogenic treatment including microstructure and wear resistance. Two cryogenic treatment methods including cryogenic treatment at −80 °C (CT) and deep cryogenic treatment at −196 °C (DCT) as well as conventional heat treatment (CHT) were carried out after carburizing process. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffractometry (XRD) were employed for microstructure characterization. The wear resistance was investigated by ball-on-disc sliding wear test on a multi-functional tribometer. The results show that the wear resistance of the experimental steel has been improved by 17% due to CT and by 25.5% due to DCT when compared to CHT. This significant improvement in wear resistance after cryogenic treatment is attributed to the microstructural changes including the finer martensitic structure, the reduction of retained austenite and the development of fine and more numerous carbides. Among these factors, the precipitation of fine carbides plays a more prominent role in enhancing wear resistance.


Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1038 ◽  
Author(s):  
Pello Jimbert ◽  
Maider Iturrondobeitia ◽  
Julen Ibarretxe ◽  
Roberto Fernandez-Martinez

The effects of deep cryogenic treatment (DCT) on the wear behavior of different tool steels have been widely reported in the scientific literature with uneven results. Some tool steels show a significant improvement in their wear resistance when they have been cryogenically treated while others exhibit no relevant amelioration or even a reduction in their wear resistance. In this study, the influence of DCT was investigated for a grade that has been barely studied in the scientific literature, the AISI A8 air-hardening medium-alloy cold work tool steel. Several aspects were analyzed in the present work: the wear resistance of the alloy, the internal residual stress, and finally the secondary carbide precipitation in terms of lengths and occupied area and its distribution into the microstructure. The results revealed a reduction in the wear rate of about 14% when the AISI A8 was cryogenically treated before tempering. The number of carbides that precipitated into the microstructure was 6% higher for the cryogenically treated samples, increasing from 0.68% to 0.73% of the total area they covered. Furthermore, the distribution of the carbides into the microstructure was more homogenous for the cryogenically treated samples.


The published information on ferrous and nonferrous metals especially Aluminium alloys subjected to deep cryogenic treatment (DCT) have yielded much improved mechanical, tribological and thermal properties resulting in improved properties in the field. Keeping the above aspects in view, tribological studies have been taken up in this work with the main objective of evaluating the wear resistance of the most used Aluminium alloys viz: Al 6061 samples at cryogenic temperature and subjected them to deep cryogenic treatment for temperature . The novelty of the work lies in conducting the wear test in cryogenic atmosphere which is the first of its kind as meagre report is available. It is observed from the wear data that the slide wear resistance and coefficient of friction evaluated in the laboratory conditions show superior wear resistance for the load application of 40N and 50N and lower friction levels for the samples subjected to sliding at cryogenic temperature as well as for the samples deeply cryo treated compared to the untreated ones. The data have been substantiated by Scanning Electron Microscopic features (SEM).


Author(s):  
Kaweewat Worasaen ◽  
Piyada Suwanpinij ◽  
Karuna Tuchinda

This research aimed to investigate the microstructure modification mechanism used to improve the hardness and wear resistance of SKH51 steel. The cryogenic treatment (CT), including both shallow cryogenic treatment (SCT) and deep cryogenic treatment (DCT), was used to modify the microstructure of SKH51 steel in this research. The effect of short and long holding time (12 and 36 h) in CT was studied. The microstructures were evaluated by using a light optical microscopy (LOM) and a scanning electron microscopy (SEM). The phase identifications of the matrix, carbides, and a-parameter of the matrix were analyzed by using X-ray diffraction (XRD). The M6C and MC carbides size, aspect ratio, and distribution were analyzed using digimizer image analysis software on the SEM micrographs. Micro-Vickers were employed to evaluate the hardness of the targeted samples. Wear tests were performed by using a 6 mm diameter WC ball as the indenter and 5-N-constant load with a ball-on-disk wear tester. The results suggested that the increase of the secondary carbide was caused by the contraction and expansion phenomena of the matrix’s lattice, forcing the carbon atom out and acting as the carbide nucleation. The influence of holding time in the SCT and DCT regions was different. For the SCT, increasing the holding time increased the volume’s fraction of MC carbide. Conversely, the M6C carbide size grew with increasing holding time in the DCT region, while no significant increase in the number of MC carbide was observed. The cryogenic treatment was found to increase the volume fraction of the MC carbide by up to 10% compared to the conventional heat treatment (CHT) condition in the SCT region (both 12 and 36 h) and DCT with 12 h holding time. Due to the microstructure modification, it was found that the cryogenic treatment can improve material hardness and lead to an increase in the wear resistance of SKH51 by up to 70% compared to the CHT treated material. This was due to the increase in the compressive residual stress, precipitation of the MC, and growth of the M6C primary carbide.


2013 ◽  
Vol 311 ◽  
pp. 477-481
Author(s):  
Yuh Ping Chang ◽  
Huann Ming Chou ◽  
Jeng Haur Horng ◽  
Li Ming Chu ◽  
Zi Wei Huang

The bad quality of machining surfaces caused by the micro wear of pressing parts has been a very big trouble for the engineers over the past decades. In order to decrease the surface wear, the technology of heat treatment is used popular. Many papers about the heat treatment technology had been proposed. Especially, the deep cryogenic treatment has been used widely for the purpose of wear-resistance in the industry. Moreover, the method of using variations of surface magnetization to monitor the dynamic tribological properties between the metal pairs has been applied successfully by the author. Therefore, this paper is base on the above statements to further investigate the tribological properties of the tool steel by deep cryogenic treatment. It can be clarified for effects of different deep cryogenic treatment temperatures on wear-resistance of the tool steel DC53. Besides, the purpose of better quality and faster product speed of the pressing process can then be obtained.


2015 ◽  
Vol 798 ◽  
pp. 395-401 ◽  
Author(s):  
S.A. Sonawane ◽  
V.K. Tripathi ◽  
S.D. Ambekar

The technique of cryogenic treatment of cutting tools is an inexpensive permanent treatment process that improves the physical and mechanical properties of materials such as metals, plastics and composites. It promotes the transformation of the retained austenite into martensite at cryogenic temperatures and also facilitates the formation of fine carbides in the martensite, thereby improving the wear resistance.This paper compares the wear behaviour of hardened and triple tempered AISI M2 high-speed steel and the same steel that was hardened and triple tempered in conjunction with a deep-cryogenic treatment at 88K for 16 and 24 hours. Test materials were subjected to wear tests on pin-on-disc machine in dry sliding condition. Equations are developed for predicting the wear resistance of M2 tool steel material. The hardness data wear loss and microstructure throw light on the improvement in wear resistance property of the M2 tool steel.It is demonstrated that the properties of the cryogenically treated samples are superior to those of conventionally treated. 24 hours cryogenically treated hardened and triple tempered M2 tool steel shows excellent wear resistance properties over 16 hours cryo-treated M2 and conventionally treated M2 tool steel material.


Author(s):  
Alireza Darvishi ◽  
Aria Daneshmayeh ◽  
Alihosein Salehi ◽  
Mahdi Ahmadi ◽  
Alireza Soleymani

In the present study, microstructure, hardness, and abrasion resistance of a heat-treated high carbon-high chromium steel (FMU-11) used in the cement mills were investigated. To investigate the best heat-treating cycle for the FMU-11 steel, three sets of samples were heat treated. The first set was tempered two times, the second set was re-hardened, and the third set was cryogenically heat treated. These samples were then compared with the conventionally heat-treated samples. The samples' microstructure was studied using an optical microscope, where traditional black and white etching, as well as color etching, were used. Scanning electron microscopy (SEM) was applied for higher magnification studies and in-depth analysis of the chemical composition. The mechanical properties were investigated by measuring the hardness and the wear resistance for the samples heat-treated in different cycles. The results showed that the cryogenic treatment and double-tempered samples had the highest hardness and wear resistance. In addition, the results showed that the re-hardening operation caused the carbides to be finely separated and evenly distributed in the steel matrix. The wear test results illustrated that the wear mechanism could be the delamination wear and the abrasive wear combined.


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