SE452992B - PROCEDURE FOR HEAT TREATMENT OF AN IRON-NICKEL-CHROME ALLOY - Google Patents

Description

EXAMPLE I An alloy having the following composition was subjected to various thermomechanical treatments, as described below: TABLE I Nickel - 45% Chromium - 12% Molybdenum - 3% Silicon - 0.5% Zirconium - 0 .05% Titanium - 2.5% Aluminum - 2.5% Carbon - 0.03% Boron - 0.005% Iron - residue The previous alloy was gamma-prime-reinforced superalloy. The following Table II lists the various thermomechanical treatments to which the alloy listed in Table I was subjected; while Table III lists the resulting microstructural and mechanical properties of the alloy after heat treatment: TABLE II Designation Thermomechanical treatment, AR 1o28 ° c / 1 hour / Fc + 60% cw IN-1 * 9a2 ° c / 1: im / Ac + 7sa ° c} 1 tim / Ac + 12o ° c / 24 tim / Ac IN-2 * s9o ° c / 1 tim / Ac + soo ° c / 11 tim / Ac + 7oo ° c / 2 tim / Ac Ec * 927 ° c / 1 hour / Ac + soo ° c / 11 hours / Ac + 7oo ° c + 2 hours / Ac En * soo ° c / 11 hours / Ac + 7oo ° c / 2 hours / Ac * After 1o3e ° c / 1 hour / Fc + sus cw 10 15 20 25 30 2? 452 992 TABLE III sso ° c Meaning- Breaking strength Comment hot (ksi) 80 ksi SR (hr) AR No gamma prime, high dislocation density - 67.9 IN-1 Bimodal gamma prime, recrystallized above gamma prime solvus 151.5 0.8 IN -2 Trimodal gamma prim (dislocation) 141.3 81.9 EC Trimodal gamma prim recrystallized above gammaprim solvus - 64.7 EE Bimodal gamma prim, equiaxial cells - 235 As can be seen from Table III above, ECf treatment produced higher stress fracture properties than treatment IN-1. The EC treatment resulted in a trimodal distribution of gamma prim, because the recrystallized annealing was below gamma prim solvus and resulted in the precipitation of a small volume of large (approximately 600 nm) gamma prim precipitates.

Of the treatments listed in Tables II and III, three treatments produced structures with dislocations. These were treatments AR, IN-2 and EE. Stress stress data in Table II revealed that heat treatment EE produced a noticeably stronger material.

This structure consisted of a woven dislocated cell structure, which was attached by a bimodal gamma-prime distribution. This condition had the highest strength of all tested and was very stable due to the attached structure of the dislocated cells.

The curve shown in the attached figure illustrates the swelling behavior of the alloy given in Table I in three thermomechanical states, ST, EC and EE. Swelling as a function of temperature in the curves is for radiation doses of 30 dpae, which is equivalent to 203 Mwd / MT (ie greater than the target radiation of 120 Mwd / MT). The data reveal that the ST and EE treatments produced the lowest swelling in the alloy listed in Table II above. The EC treatment produced an acceptable level of swelling of target radiation, but the treatment was far from the optimum for in-reactor applications. 10 15 20 25 30 4552 Sauce 9592 for comparison exposed alloy with the following summary for tenmmemic treatments similar to those mentioned above.

TABLE Iv _ Nickel 60 Chromium 15 Molybdenum 5.0 Niob 1.5 Silicon 0.5 Zirconium 0.03 Titanium 1.5 Aluminum 1.5 Carbon 0.03 Boron 0.01 Iron residue The thermomechanical treatments given to the mentioned alloy in table IV and the microstructure and mechanical properties of the resulting alloy are given in the following Tables V and VI: TABLE V Designation Thermomechanical treatment * BP 1c3e ° c / 1 hr / Ac + eoo ° c / 11: im / Ac + 700 ° c / 2 tim / Ac BR 927 ° c / 1 tim / Ac + 9oo ° c / 11: im / Ac + 7oo ° c / 2 tim / Ac 'BT 1o3a ° c / 0.25 tim / Ac + a99 ° c / 1 tim / Ac + 749 ° c / 8 tim / Ac cm 30% ww vid 1o3s ° c + soo ° c / 11 tim / Ac + 7oo ° c / 2 tim / Ac cu a9o ° c / 1 tim / Ac + aoo ° c / 11: im / Ac + 7oo ° c / 2 hrs / Ac + 30 BU aoo ° c / 11 hrs / Ac + 7oo ° c / 2 hrs / Ac * After 1o3a ° c / 1 hr / Fc + 60 % cw AC means air-cool, air cooling; FC means furnace-cool, oven-cooling; CW means cold-working, cold-working. 10 15 20 25 30 äs 452 992 5 TABLE VI sso ° c Beteck- Brotthållfast- 80 ksi SR ning Kommentar het (ksi) (tim) BP Small gamma prime, no dislocations 136.7 -, BR Bimodal gamma prime, gamma cells 152.5 73 BT Bimodal gamma primer, no dislocations 135.3 - CT Bimodal gamma primer, non-uniform structure (long-banded cells, some lower grains) 154.6 - CU Bimodal gamma primer, elongated cells 147.0 - BU Bimodal gamma primer, equiaxial cells 156.4 74 Gamma primer solvus and one-hour recrystallization temperature for the alloy indicated in Table Iv were 91s ° c ¿1o ° c and 1ooo ° c ¿2o ° c respectively. Therefore, unlike the alloy given in Table I, there was no temperature range in which recrystallization could be performed while aging. Accordingly, the treatments BP and BT, which involved annealing at 1038 ° C and subsequent double aging, both produced a dislocation-free austenite matrix and a bimodal gamma-prime distribution. Structures produced by treatments CU and BU, which did not induce recrystallization, all contained a highly dislocated cell structure containing various distributions of gamma primer.

Table VI is a summary of the observed structures and corresponding physical properties. Note that the mechanical property values are grouped into two classes. These are non-dislocation densities, gamma-prime-containing structures having 650 ° C, breaking strengths between 135 and 137 ksi and the dislocated gamma-prime structures, which are much stronger, with breaking strengths between 147 and 157 ksi. Due to their superior strength and due to the advantage of an increased incubation time for swelling, dislocated structures are preferred. In 1 Treatment CU given in Tables V and VI above started with a dislocated cell structure with a trimodal gamma-prime distribution, which was then cold processed 30%. Namely, the final cold processing decreased as indicated by the 650 ° C breaking strength data given in Table VI, apparently by destroying the integrity of the dislocation cell walls.

The treatments BR and BU in the alloy listed in Table IV both produced a highly dislocated, partially recrystallized or recycled cell structure with bimodal gamma prime size distribution. The BU treatment was preferred because it gave slightly lower stress-breaking properties than the BR treatment. The dislocation and gamma primer structures for the BU treatment produced a cell structure that was much more dispersed and woven than that produced by the EE treatment of the alloy listed in Table I. The minimum cell thickness of the BU treatment was approximately the same as the gamma prime particle spacing .

To further demonstrate the improvement obtained by the thermomechanical treatment according to the invention, reference is made to the following Tables VII and VIII, which show that this treatment is very effective in promoting high post-irradiation extensibility.

In this connection, it would be pointed out that there is a reduction in which the extensibility of these materials is considerably reduced when tested at a temperature which is 110 ° C above the temperature at which the material has been irradiated. Thus, the worst extensibility would be where the material has been irradiated at 595 ° C. 110 ° C would account for all transient conditions for operation of Thus, the choice of the material and the heat treatment or the thermomechanical heat treatment at a temperature of 80500, e.g. a fast bridging reactor. of the material which when irradiated at 695 ° C would be tested at 805 ° C, where the lowest post-irradiation extensibility has occurred. Reference to the following Tables VII and VIII makes it quite clear that the solution-treated state of alloy D66 upon irradiation at 69590 and tested at 80S ° C exhibits zero extensibility. In contrast, materials that have been subjected to treatment specified in the appended claims of the same alloy irradiated at 695 ° C and tested at 805 ° C show that a 1.1% uniform elongation is available. It is critically important to maintain more than 0.3% extensibility under these conditions, as it is necessary to maintain fuel rod integrity under reactor transient conditions and the tables show that these targets have been achieved. Tables VII and VIII also show that the higher extensibility of this treatment is also accompanied by 452,992 higher strength, which is extremely unexpected with respect to these irradiated materials. These higher strengths also prove that the swelling resistance is excellent, as shown by the alloys subjected to this treatment. umwu mo__o mqo Nwßvv; ßïmßm oPXv orw 452 992 _.- 5000020 0.0 0.0 0.02 0.53 0.000 0.002 0:00 t000. ïâš 000 000 00.00 0000038000 0 0 0.00 0.03 _ 0.0.0 0.00 .. _7020. 000 000 00.00 0.00 0.000 ..- So 000 000: lä _. .020 00.0 0.000. 0.20,: _ 0.02 0.30 0-022. 0G 000. 00.00 00.0 00.0 0.00 0.000 0.00 0.000 0.00 0.000 ..- So 000 00 .. 00.00 00.0 00.0 0.000 0.000 0.02 0:00 0-020. 000 000 00.00 0; 0; 0.000 0.2.0 0.000 0.000 0.02 0.00 .. 0-03. 000 000 07mm 0.0 0.0 0.000 0.002 0.000 0.000 0.03 0.000 0-022. 000 000 00.00 0 :. 0.0 0.000 0.00: 0.3; 0.000 0.00- 0.000 ..- So 000 000 00.00 0.0 0.0 0.000 0:00, 0.00, 0.000 0.02 0.000 0-020 000 00 .. 00 | 0m 0.0 0.0 0.02 ... 00000500000 0.000 0.0: 0.000 Tšš .N00 000 00.00 26.0 0.0 AE Nneufawwšä u .Ãw fi m Swaäuz 00,000. 0 0 .nä 0% 09. 0% 000. E: .Tä fl Se. 60.. .cwn fl umu. .H08 uw fi äw. .å fi m šë fi m fi m .äE .93 .man så H30 _ H38 ... noëä .Aä fi åä .. E ._0000 .âwuam Så 50308 èëš E fl am fi wnnm fl èä m fi äww fl mšš 0000330302. 0.00 u fi müâm w mwâm mwâm mwâmw mwâmw mwâmw mwâmw mwâmw mwâmw. m w.ßmw W m. ° w N P.mmm m | oPx «W OF» W oow fßßfam M ß.m ßww m.mmP ~.> m ° ~ M o_o «- m.mmm W ~ _- ~ W >. ~ vw ~ | oPx «W op» M cow «> | am M _. @ -.Q w_> o ~ w_ ~ w«. W m_w> P m.Po ~ PW ~ .owf _ o. «° PP« | oPx «~ m ~ M Qom Pßfsm« ~ m «.m W o_-N wP @« ~ _ m.ø@F ~. ß «~ P _P.mwP ß \ mwPf v | o-xw ~ m ~ _ cow .ßofam wm« .m _> _o- «. ~ m« F m.owP w. ~ «~« W ~ _ ~ w ~ o.mmPP «| o_x« www omm mmnem .ccwgwm wwm fl wo fi wwxwæmmwmmmmwwomw mf ~ P. ~ .mwP ~ m_m «~ w ~ mooF« | o ~ x «u ° .w W oem, _m | am u _ _ H Jc fi muvm .E02 u mmèä» mßw fl ßuwmm _ ~. ~ * ___ _ ~ .m> M o . «Om om @ N -mm«. ~ .m «W« _mmm «| oPx« wow www wæ «« am °. ~> ~ _ W w.mF ~ "ß.« m ~ F-oF M o. «o> m. >> U m. @mm «| oFx« or »oow Ww-fam w. ~ m. ~ W w ~ = m, m.wm ° P> .mm_ W m.mmm Fm ~« wm >> «| ° Px« omm 0mm. moo | am ß., «.P _ ° .ßß ~ W m. ° -P w. ~ w ~ M @ _- ~ F> .m ~ P m ~ www M vlofxw orm com Wmmxem ~ .FW m .. _ M -.wm_M o- @ ~ «mm> P. M_ @ mPP m.omf. @ _ @ Mw _« 1Qfx «owm om« _M_ ~ | am mm m. ~ .W.moF m. «.Mm« _w, w ~ _w> Û> _wmm W w | ofx «mwß mmß Wmqnam m ~ w .w- m., mF« .m ° m m_ «FF« .mw> @_> m W> _ ~> @ W «| Ofx« mmm mmm M @ ~ | am www «.m ~. ° w_ w. ~ P- ~ ._wF mP- m_ ~ mP M m_wFm W« | oPx «Qom acw W_« | am P. «-« w.wm- «.mwmP> _m @ _ m_mwF ~«. «m ~ W m ~ w ~ m M vuø-xw omm omm __m | am xm fl m F fl m oo ° ~« .m> mP m_o> P «~ m> ff> _ ~ m «_ m_ ~ moF“ «| o« x «Qom som W>« | am www w. ~> .mo ~ «. @ _« P «_PwP m_Qm- m.« w ~ w_ «m_ ~ @ «| Q ~ x« conv om «Nwaam> .m> .m ø.Fø ~ w.mmmf w.~@f _.« F ~ F ~ .QmF w_mmofm <| ° Fx «Nmw mmß omnam æ ~ «W.« Om ° ~ Qf «« f ~ .N>. M.ßwff w.øwP> .wøfFM v | o_xv ~ m ~ mmm .mwnam m. «M.« ».Mv ~ mP ~> f w. mF ~ °. «>« - m_> w ~ m_mm ~ _W «| o-xv ~ m ~ ømw omuam _.> wz«. ° A m. ~ | su | c- @ Px «.c fl wuum .aoz mm wwn _ _ _ ß. mmnwwn m: fi Hwmu fl mmn flfi x0m> ud vmawnvmmncouv fl m fl mon nwumzuw fl w fi awnmønn HHH> QANMQB

Claims (7)

452 992 P A T É'n T K R A v Process for heat treatment of an iron-nickel-chromium alloy consisting essentially of from 25% to 45% nickel, 10% to 16% chromium, 1.5% to 3% molybdenum or niobium, from 1% to 3% titanium, from 0.5% to 3% aluminum and the residue essentially only iron, characterized in that the alloy is kept at a temperature in the range of 100,000 to 1100 ° C for 30 seconds to 1 hour followed by oven cooling and cold working of the alloy 10% to 80%, that the alloy is kept at a temperature of from 750 ° C to 82500 for 4-15 hours followed by an air cooling. after which the alloy is heat aged at a temperature in the range '650 ° C to 700 ° C for 2-20 hours followed by an air cooling. Process according to Claim 1, characterized in that the alloy is initially heated to a temperature in the range from 10 ° C to 100 ° C for 2-5 minutes. 3. A method according to claim 1 or 2, characterized in that the alloy is cold worked by cold rolling 20% to 50%. 4. A method according to claim 3, characterized in that the alloy is cold rolled 30% to 50%. 5. A method according to claim 1, characterized in that the alloy is in the form of a tube and is cold worked by drawing the tube to give a reduction of 15% to 35%. Process according to Claim 5, characterized in that the reduction is in the range from 20% to 30%. 7. A method according to claim 1, characterized in that, after cold working, the alloy is heated to a temperature of about 775 ° C for 8 hours followed by an air cooling. J |