IIIIIIIIIIIITIIIIIIIIIIIII ~IIIII - BUET

It has been found that the addition of sulfur to water leads to the formation of Fe-52 in the composite layers of illild steel samples. 34. The brightness and dispersion influence the height attainment, s.. The surface height obtained by. the processes CClrlJllri,;~ng ana. The formation of the high, gll llitrl[)geli fils in the nitrided case increases the corrosion resistance of st8cl in dtj-ospl,-,rl.c air, frcsh water, superh8at8d steam

5.5 6.08 '/, NITROGEN

LIQUID NITRIDING

This syn'ultancous satuI"

Chapter-2

LIQUID NIT RIDING

IN UREA-SODA BATHS-A SURVEY

Careful inspection necessary for satisfactory operation. Proper maintenance and additions must be made to the composition of the bathroom. No nitrldlng could then be carried out and the bath salts had to be discarded. This gradual introduction into the clmount of carbonate is not unexi'ectcd Lceau,-e in Helting eyaradc is formed in the bi;lth.

Chapter -3

MATERIALS AND METHODS

Controlling pyrometer

OPTICAL METALLOGRAPH¥

One of the main reasons why we chose llJ.tr:Lding treatment for machinery and tools is to improve the wear resistance and dry running properties of the milteriil. It is generally believed that wcar-rCslstancc lnLprUVes with Inc-'rca5ing Cilse hardness. The wear loss gauge is performed on a simple wear pin made of nitrogen material that flows.

To achieve the actual operating conditions under which nitriding is said to significantly improve the wear resistance of a material, the tests were conducted under normally dry conditions. temperature affects the wear properties of thG materidl and also to find out that the addition of sulfur to the bath helps to improve the quality of the bath. The purpose of the X-ray diffraction studies was to determine the structure of the layer formed on the surface during bath diving.

Mild steel samples hzlvc hecn liquid nitrided in urea-sodll baths in the temperature range 525 - 575°C lind for times up to 5 hours trc8tlronL The effects of nitriding in this bath have been followed by optical metallography, microhardness measurements and x-ray diffraction techniques. Relative wear measurements h,"vc also performed Olie a pin-on-disc" type appllrlltuB designed and flibriclltcd in the department of rr.etal-. 4.4 6how the variation in the thickness of the conpouna l,'lyer for"ed on the ",lId steel samples treated in urell-soda eder.

The nature of the curves indicates that Inyer's growth is diffusion controlled and the COMPLETE results are consistent with what he expected.

HARDN8SS M~ASUREMENTS

Hardness versus pelletratlon-dlstallCe pro£ll06 uses useful information regarding the depth of penetration of llltrogen. FIG.4.6 VARIATION IN SURFACE HARDNESS WITH TREATMENT TIME OF MILD STEEL SPECIMENS LIQUID NITRED IN UREA-SODA BATHS. FIG.4.7 EFFECT OF SULFUR ADDITION ON SURFACE HARDNESS OF STEEL LIQUID NITRIDED IN UREA-SODA BATHS,.

FIG.li.9 VARIAFION IN HARDNESS VERSUS PENETRATION 'DISTANCE PROFILES WITH TREATMENT TIME OF MILD STEEL SPECIMENS LIQUID NITRIDED AT 550"C IN UREA-SODA BATH. F1G.4.10 VARIATION IN THE HARDNESS MIG. LD STEEL SPECIMENS LIQUID NITRIDED AT 575 DC IN UREA-SODA BATH. From these figures, it can be seen that the depth of the case, i.e. the distance at which the slope of the hardness in relation to the penetration distance profiles becomes minimal, increases with increasing form of treatment at a certain temperature and also with the temperature ilt constant tn"atment time.

A comparison9 of case depths produced by nitriding in conventional baths and in edes based on UrCasoda, hilS shawn producing nitriding in urea-soda baths. The deeper penetration of nitrogen causing nitration in urea-soda baths, leading to greater depths, has been attributed to the formation of an~onia gas, ill the b~th. FIG.4.12 VARIATION IN CASE DEPTH WITH TREATMENT TIME AT DIFFERENT TEMPERATURES OF MILD STEEL SPECIMENS.

FIG. 4.13 HARDNESS VARIATION IN COMPARISON OF THE "DEVIATION PROFILES" OF P.ENE.TRATION WITH TIME OF PROCESSING LIQUID SOAP_STEEL (~NITRIDED AT 75°C IN" URE~- SODA BATH Z.

FIG. 4.11 VARIATION IN HARDNESS VERSUS PENETRATION DISTANCE PROFILES WITH TREATMENT TEMPERATURES OF MILD STEEL SPECIMENS LlQUtD NITRIOED FOR 2 HOURS IN UREA-SODA

575°C (Sulphur)

X-RAYDIFFRACTION STUDIES .1 Introduction

Along with these nltr.laeS dlffraction Ilnes belonging to an unknown phase Was illso observed at all temperatures:; anei times. Since tilis pnase could not be clearly identified, the reasons for its formation could not be investigated. Both Fe3N and Fe4N were found to be formed under all investigated treatment conditions.

The results of Qbtal show that, although both Fe3N and Fe4N, the nitride layers contain a large part of Fe3N lllt-ride. It has been assumed22 that in the presence of car hlguer nitrides tend to form. _4.20 shows the diffractlon pattern of a mila sample St;Celmen llquid nitl: idea in urea soda baths in which 2 percent sulfur was added as Na2S.

Sulfur turned out to be definitively present in the COfolp01.111d layer, possibly as FeS2, but unfortunately the lines could do so. When treated, the temperatures result in an increase in voltage of 5 V (Fig. 4.6).

4.0 HRS,

BATHS,

FIG,~,23 COMPARISON OF WEAR - RATE OF LIQUID STEEL SPECIMENS NITRIDED AT 575°C IN UREA-SODA BATHS WITH AND WITHOUT SULFUR ADDITION. The maximum wear resistance on the plates", studles I have found to correspond to the maXl hardness of the surface of the nitrldeclR specimen. therefore it appears clear.

In addition, ilppcars th.lt for maximum wear resistance). Therefore, the prayer III thc=se biltlls should be performed, for a long time in the lowest time [JDril- turDS. The addition of sulfur is seen to cause a decrease in the wear UI of the wild steel sample; nicridea 1n these baths. It may be mentioned that the addition of sulfur causes an increase 1n the surface hardness values of the nitrided liquid in urea-soda baths, and therefore an increase in our soft steam resistance. ur"

SUMMARY AND CONCLUSIONS

I S\J~IHARY AND CONCLUSSIONS

I. 2 SUMMARY

CONCLUSIONS

Appendix-A

IDENTIFICATION OF PHASES

Cullity disproved the detailed analysis of the X-ray diffraction pattern and all the assumptions that went into this work. The ClnCllytlcal method used for id.entificat.L011 or pn,Jses involves altmCltic ~lanipulation of OlJlOCrVeQ. The other nitrium formed appears to be Y-nitrio (Fe4N). Electron diffraction studies of this phase have shown that th".

The y'_ phase has a face-centered CUblC tight confinement .lron ilto;ns \1ith nltrogen il'toms equidistant from each other and occupying a quarter of tne nurrb8r octahedral inner ices in il co:upl"tely orcier "d " .:Inner. It was previously not possible to confirm the tentative identification of the diffraction lines belonging to this phase (Ta.ole A-4) by actual calculations. In addition to those belonging to f'e3N and Fe4N nitr.1des there are several other diffraction lines lines that would not be clearly recognizable.

Attempts to match these elements to those of the 11 possible elements in the mild steel samples were unsuccessful. In the present study, we also thoroughly tested the presence of elements such as Cr, Mo, V, W. Finally, additional diffraction lines that appeared in our sulfur-containing baths were listed as shown in {Table A-7 ).

A tentative match was obtained by reference, g to the l-nOeXto LULJ ul-fraction data file and they were found to belong to F0S2,.

34;Improving Diesel Engine Reliability by Su1fo-nitrldlng Cylinder Liners in Salt Batns", Prat, Control Ind. Kurny, "Un tile Liquid Nitr~ding of En 40B Steels ~n Urea-Soaa Baths", Banglad8sh Journal of Scientific Research, Vol. Schematic diagram of gas-fired liquid (urea-soda batn) rut)::iding furnace with ilutomatic control system .. sulfur Bath for 3 hours at

Variation in thickness of composite layer "'lth tn"atment tilL'" a' different temperatures of rrild stee 1 liquid nitrided specimens in. IT. cold liquid nitrided steel specimens in . urea-soda baths. Effect of the addition of sulfur to the hardness of the liquid nitride surface of steels in the ur-e,-soda bath.

4. 8 VilriatJ-on in hardness ve~'sus penetr-ation dista.nee profiles with treatment time of n,ild steel.l Sp'Cl-)fens with liquid nitride at 525 °C in urea. - soda. VilJ:iation in Cilse depth with treatment time at different temperatures of D,ild steel samples. Effect of sulfur addition on case depth of mild steel liquid nitrided in sodium urea.

Variation in wear rates with treatment temperatures of rr.ild steel specimens liquid nitrided in ured-soda laths.