Subject to a continuing debate, cryogenic treatments of alloy steels have been claimed to significantly increase wear resistance and toughness through the interplay of three effects: completing martensitic transformation, promoting uniform precipitation of fine carbides and imparting residual stresses. This study reexamines effects of various heat-treatment schedules including cyclic heat treatment at (690 C) and cyclic cryogenic(Shallow) treatment at (-85 C) onmicrostructure and selected properties of Stainless steel 316L.Examination methods include SEM,, micro hardness, Charpy impact, wear resistance measured using the standard pin-on-disk technique adopted from the field of thin-film technologies. Results confirm the cryo-treatment enhanced precipitation in the subsequent tempering step of what turns out to be 100-250 nm alloydepleted carbides, and moderate improvements in wear resistance and hardness, both scaling with the cryogenic treatment time and at the cost of reduced impact resistance and also corrosion resistance. Reported results and correlations shows that it is mainly suitable for automobile industries

Maadesh Kumar, K

P, Sathish kumar

Sivaraman, M

Venkatesh, M

International Research Journal of Automotive Technology (IRJAT)

        
 
 
 
 
 
 
 
INTERNATIONAL RESEARCH JOURNAL OF AUTOMOTIVE TECHNOLOGY (IRJAT) 
 
http://www.mapletreejournals.com/index.php/IRJAT                   
Received 26 March 2018                   ISSN 2581-5865 
Accepted 27 March 2018                     2018; 1(2);85-90 
Published online 30 March 2018 
INVESTIGATION OF MICROSTRUCTURE OF CYCLICALLY CRYOGENICALLY TREATED 
SPECIMENS OF SS316L AND COMPARISON OF ITS MECHANICAL PROPERTIES WITH 
CYCLICALLY HEAT TREATED SPECIMENS USING IN AN AUTOMOBILES. 
P.Sathish Kumar1*, M.Sivaraman1,K.Maadesh Kumar1, M.Venkatesh2 
1Asst Professor, Dept of Mech Engg, Jansons Institute Of Tech, Coimbatore, Tamilnadu, India. 
2Student, Dept of Mech Engg, SBM College of Engg and Tech, Dindigul, Tamilnadu, India. 
* E-Mail ID: kumarsathish0035@gmail.com, Mobile: 9698175302 
ABSTRACT 
Subject to a continuing debate, cryogenic treatments of alloy steels have been claimed to 
significantly increase wear resistance and toughness through the interplay of three effects: 
completing martensitic transformation, promoting uniform precipitation of fine carbides and 
imparting residual stresses. This study reexamines effects of various heat-treatment schedules 
including cyclic heat treatment at (690 C) and cyclic cryogenic(Shallow) treatment at (-85 C) on 
microstructure and selected properties of Stainless steel 316L.Examination methods include 
SEM,, micro hardness, Charpy impact, wear resistance measured using the standard pin-on-disk 
technique adopted from the field of thin-film technologies. Results confirm the cryo-treatment 
enhanced precipitation in the subsequent tempering step of what turns out to be 100-250 nm alloy-
depleted carbides, and moderate improvements in wear resistance and hardness, both scaling with 
the cryogenic treatment time and at the cost of reduced impact resistance and also corrosion 
resistance. Reported results and correlations shows that it is mainly suitable for automobile 
industries. 
Keywords: Cryogenic Treatment, Hardness, SEM analysis 
1. INTRODUCTION 
Steel is widely used in the various engineering application such as automotive, 
agricultural, constructional purposes etc. Steel generally contains 0.02–2.1% carbon content and 
depending upon the need of industry steel is selected for different processes. After that there are 
different types of heat treatment processes which used for improving its various mechanical 
properties by altering the microstructure of steel. Properties of heat treated specifically depend on 
three different phases such as heating temperature, soaking period and cooling rate. Over the past 
few decades, extensive interest has been shown in the effect of low-temperature treatment on the 
performance of stainless steels [1, 2, 3]. Low-temperature treatment is generally classified as 
either “Shallow Cryogenic treatment” at temperatures down to about −85 C or “Deep Cryogenic 
treatment” at liquid nitrogen temperature of −196 C [5].Cryogenic treatment is not a substitute for 
heat treatment, as often mistaken for, but it is a supplementary process to conventional heat 
treatment before tempering [2, 5].Cryogenic treatment is an optimal method for reducing percent 
of retained austenite. Cryogenic treatment consists of heating steel up to austenite temperature, 
cooling it in quench environment and then immediately putting it in sub- zero centigrade degree 
and then tempering heat treatment. Increasing resistance to wear, reduction of internal stresses, 
consistency of dimensions and deposition of micro carbides in the field can be regarded as the 
most important privileges of using cryogenic heat treatment. The less the temperature of 
cryogenic environment, improvement in properties is performed with more rapidity. [4] With 
P.Sathish Kumar  et al. / International Research Journal of Automotive Technology 2018; 1(2): 85-90 
cryogenic treatment applied immediately after quenching, residual austenite is reduced, and spots 
for the nucleation of -carbides created during tempering are created in martensite.  
Cryogenic treatments can produce not only transformation of retained austenite to 
martensite, but also can produce metallurgical changes within the martensite. This offers many 
benefits where ductility and wear resistance are desirable in hardened steels [6] Previous research 
studies mainly focuses on the enhancement of the properties of high speed steel, tungsten carbide, 
aluminum, die steel and its micro structural changes. The objective of this work was to investigate 
the effects of cyclic cryogenic treatment in conjunction with the inter critical heat treatment on the 
wear behavior, hardness and microstructure changes in stainless steel 316L. 
2.SUMMARY OF LITERATURE REVEIW 
Recent studies have indicated that cryogenic treatment is an essential supplementary 
treatment, which is performed on products after conventional heat-treatment in order to increase 
their wear resistance in some materials and to produce dimensional stability in others. The 
cryogenic treatment is conducted on stainless steels, tool steels, maraging steel, cast iron, 
carburized steel, tungsten carbide, polymers and composites. In all of the materials mentioned, the 
cryogenic treatment increases the wear resistance and subsequently increases the product life. The 
cryogenic treatment has been used as a finishing process in the past few decades. This process is 
also being used in aircraft and automobile industries as well as many other areas.Over the last 
decade, several researchers have reported that the Cryogenic Treatment (CT) considerably 
improves the wear resistance (WR) of steels than those obtained either by Cold Treatment (CT) or 
by Conventional Heat Treatment (CHT). In addition, it has also been reported that Cryogenic 
Treatment and multiple tempering after cryogenic treatment enhances the dimensional stability 
and reduces the residual stresses. These positive effects increase the service life of the components 
made of AISI 316L stainless steels. Literature of past work does not adequately clarify the 
selection of tempering, cryogenic temperature and soaking time. There is a need to standardize the 
process for cryogenic treatment in particular stainless steels and understand the underlying 
metallurgical mechanism responsible for improvement of wear and changes in microstructure 
during cyclic cryogenic treatment. In general, cyclic cryogenic treatment and multiple tempering 
are still in the dormant level as far as microstructure level study is concerned. This is the main 
focus of the present work on Stainless steel 316L. 
2.1 Problem Definition 
Effects of cyclic cryogenic treatment on microstructure and physical properties of stainless 
steel 316L and comparing its physical properties after each cycle of the cryogenic treatment with 
that of each cycle of conventional heat treatment. 
2.2 Objectives 
Therefore the present investigation is based on the effect of cyclic cryogenic and heat 
treatment and study of its various properties after each cycle on stainless steel 316L and has 
following objectives, 
1)To make a comparative study on the hardness of cyclically cryogenic treated SS316L samples 
with that of cyclically heat treated austenitic stainless steel of grade SS316L.  
2)To study the effect of cyclic cryogenic treatment on the microstructure of cyclically cryogenic 
treated specimen and compare with cyclic heat treated specimen.  
3) To study the micro structural changes using optical microscope and SEM. 
P.Sathish Kumar  et al. / International Research Journal of Automotive Technology 2018; 1(2): 85-90 
4)To study the corrosion behavior after cyclic cryogenic treatment using intergranular corrosion 
test(IGC) using practice E  
5)It is intended that, this research will be useful in promoting the applications of cryogenic 
treatment on stainless steel 316L.  
3. EXPERIMENTAL PROCEDURE 
The investigations were made by using the specimen made from the sheet having 
dimensions 300mm wide & 10 mm thick. After that the specimen were divided into two groups A 
& B. First of all the group A specimen were heat treated in a muffle furnace at a temperature of 
690o C for about 60 minutes followed by cooling it down in the furnace then this is continued for 
three different cycles. The Group B specimen were shallow cryogenically treated at a temperature 
of -85 0C having soaking period 12 hours under controlled conditions followed by tempering at a 
temperature of 240 0C for about 1 hour and this is repeated for 3 consecutive cycles. Treatment 
process of the specimen are shown in Fig.1.The samples of the group A & B were then subjected 
to microhardness test to study the effect of shallow cryogenic treatment over cyclic heat treatment. 
Then we study the microstructure of the group B specimens after each cycle of shallow cryogenic 
treatment 
3.1 Intergranular Corrosion Test 
The specimen was prepared according to ASTM standards (60 x30x4mm) the specimen 
was kept in acidified copper sulfate solution by dissolving 100 gm of copper sulphate, 700ml of 
distilled water and 100ml of sulphuric acid solution and diluted to 1000 ml with reagent water. 
The specimen was put in the solution for 2 days and the bend test was conducted on shallow 
cryogenically treated specimen for three cycles and no fissures or intergranular cracks were 
formed on the surface of the specimen after the test. 
3.2 SEM Analysis 
SEM was carried for both cryogenically treated samples to study the microstructural 
changes. Results of the SEM analysis are shown in fig. 3.3.1 and fig. 3.3.2 for cryogenically 
treated corroded and uncorroded SS316L samples respectively. The results showed the presence 
of the fine precipitated carbide particles in case of cryogenically treated samples which verify that 
the refinement of carbides takes place after the cryogenic treatment. 
                                           
Fig.1 SEM image of stainless steel 316l after corrosion test 
 
P.Sathish Kumar  et al. / International Research Journal of Automotive Technology 2018; 1(2): 85-90 
                                            
Fig.2 SEM image of uncorroded SS 316l after corrosion test after a single cycle of shallow cryogenic treatment 
 
                                             
 
Fig.3 SEM image of uncorroded SS 316l after corrosion test after a second cycle of shallow cryogenic treatment 
 
                                            
 
Fig.4 SEM image of uncorroded SS 316l after corrosion test after third cycle of shallow cryogenic treatment 
 
4.  RESULTS AND DISCUSSION 
Table 4.1 shows the hardness of both cyclically cryogenic treated and cyclically heat 
treated SS316L (Stainless Steel316L) samples. They are having somewhat similar result where 
there is no much variation in the hardness values of cyclically heat treated samples and cyclically 
shallow cryogenic treated samples.  
 
Table 4.1 Results of Rockwell Hardness test of cyclic cryogenic treated specimens and cyclic heat treated 
specimens 
 
Cycle Hardness (HRb) Cyclic cryogenic treated 
  
After cycle 1 83.8 
  
After cycle 2 79.3 
  
After cycle 3 76.6 
 
 
Hardness (HRb) Cyclic heat treated specimens 
  
After cycle 1 84.3 
  
After cycle 2 81.3 
  
After cycle 3 78.1 
  
P.Sathish Kumar  et al. / International Research Journal of Automotive Technology 2018; 1(2): 85-90 
 
The results obtained in the present study are in accordance with the above two tables. Even 
the micro hardness results also are not showing conspicuous variation between the cyclic shallow 
cryogenic treated and cyclic heat treated specimen. The precipitation of fine carbides during the 
cryogenic treatment cycle may affect the wear resistance and the toughness but only a small, if 
any in specimen hardness. It was seen that the hardness falls uniformly after each cycle in both 
cases i.e. the cyclic shallow cryogenic cycle and cyclic heat treated specimens. 
4. CONCLUSION        
1. The shallow cryogenic treatment makes the carbides present small in size which was observed 
from microstructure comparison of cyclic heat treated specimen and cryogenically treated 
specimen and more the cycles the more the affinity for number of carbides to be small and they 
will be lying uniformly with large carbides which may be helping to increase wear resistance .  
2. In the corrosion test, the weight loss of cryogenically treated specimen is more as compared to 
that of untreated specimen. This can be attributed to the fact that tspecimen becomes brittle after 
cryogenic treatment.  
3. As of SEM analysis, it is obvious that refinement of carbides is extra in case of cryogenically 
treated stainless steel 316L in comparison to that of cyclically heat treated specimen.  
4. There is not much difference in hardness between cryogenically treated and cyclically heat 
treated SS 316L specimens. But hardness decreases with each cycle of shallow cryogenic 
treatment  
5. It was also observed that post-cryogenic treatment fine machining (grinding) is easier in case of 
cryogenically treated specimen rather than cyclically heat treated specimen.  
6. Homogenized annealing will increase the average grain size of both pro eutectiod ferrite and 
austenite. The cyclic heat treatment will diminish the grain size of both pro eutectoid ferrite and 
austenite in case of cyclic heat treatment.  
7. As a result of repeated cryogenic treatment the presence of retained austenite is decreased.  
8. After each cycle of cryogenic treatment more the number of retained austenite is changed to 
martensite in case of cyclic cryogenic treatment.  
9. The grain structure microstructure get more and more refined with each cycle of cryogenic 
treatment. 
10. Carbon clustering decreases due to lesser the carbon density with each cycle of shallow 
cryogenic treatment which causes decrease in hardness with each cycle.  
11. After cryogenic treatment the microstructure is heated up uniformly inside the chamber which 
makes the molecules coarsen in nature hence after each cycle the molecules become coarser in 
nature which is the reason why specimen gets less hard in nature after each cycle in case of cyclic 
heat treatment.  
12. From this result we have concluded that, this material  is most suitable for automobile fields. 
 
REFERENCES  
[1]. Popandopulo, N.; Zhukova, L.T. “Transformation in high speed steels during cold 
treatment”, Met. Sci. Heat Treatment, 1980 22,(10)708–710. 
 
[2]. Mohan Lal, D.; Renganarayanan, S.; Kalanidhi, A.  
 
“Cryogenic treatment to augment wear resistance of tool and die 
steels”.,Cryogenics2001,41,149–155. 
  
[3]. Molinari, A.; Pellizzari, M.; Gialanella, S.; Straffelini, G.; Stiasny, K.H. “Effect of deep 
cryogenic treatment on the mechanical properties of tool steels”, J. Mater. Process. 
Technol.2001,118,350–355. 
P.Sathish Kumar  et al. / International Research Journal of Automotive Technology 2018; 1(2): 85-90 
 
[4]. Barron, “A Study on the Effect of Cryogenic Treatment on Tool Steel Properties”, 
Louisiana Technical University Report,August,30,1984. 
 
[5]. Barron, R.F. “Cryogenic treatment on metals to improve wear resistance. 
Cryogenics”,1982,22,409–414. 
 
[6].S. Sendooran, P. Raja “Metallurgical Investigation On Cryogenic Treated HSS Tool”, 
International Journal of Engineering Science and Technology (IJEST)Vol.3 No.5, May2011. 
 
[7].Mohan Lal, D.; Renganarayanan, S.; Kalanidhi, “A. Cryogenic treatment to argument wear 
resistance of tool and die steels”. Cryogenics 2001, 41, 149–155. 
 
[8].Bensely, A.; Prabhakaran, A.; Mohan Lal, D.; Nagarajan, G.,“Enhancing the wear resistance 
of case carburized steel (En 353)by cryogenic treatment”.Cryogenics 2005, 45, 747–754.  
  
[9].Yun, D.; Xiaoping, L. Hongshen, X. “Deep cryogenic treatment of high-speed steel and 
its mechanism”. Heat Treatment of Metals 1998, 3, 55–59. 
 
[10] P Sekhar Babu; P Rajendran; K Narayana Rao; “Cryogenic Treatment of D2 Tool Steels to 
Augment Wear Resistance”,  International Journal of Material Science ISSN 0973-4589 Volume 
4, Number 1 (2009), pp. 9–16. 
 


INVESTIGATION OF MICROSTRUCTURE OF CYCLICALLY CRYOGENICALLY TREATED SPECIMENS OF SS316L AND COMPARISON OF ITS MECHANICAL PROPERTIES WITH CYCLICALLY HEAT TREATED SPECIMENS USING IN AN AUTOMOBILES

https://mapletreejournals.com/index.php/IRJAT/article/download/20/20

INVESTIGATION OF MICROSTRUCTURE OF CYCLICALLY CRYOGENICALLY TREATED SPECIMENS OF SS316L AND COMPARISON OF ITS MECHANICAL PROPERTIES WITH CYCLICALLY HEAT TREATED SPECIMENS USING IN AN AUTOMOBILES

Abstract

Similar works

Full text

Available Versions

International Research Journal of Automotive Technology (IRJAT)