A Study of the Effect of 5 at.% Sn on the Micro-Structure and Isothermal Oxidation at 800 and 1200 °C of Nb-24Ti-18Si Based Alloys with Al and/or Cr Additions

Xu, Zhou; Utton, Claire; Tsakiropoulos, P.

doi:10.3390/ma13010245

Cited by 19 publications

(126 citation statements)

References 38 publications

(127 reference statements)

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“…In synergy with Al and/or Cr, Sn or Ge improve the oxidation resistance of Nb-silicide-based alloys in the pest oxidation regime when added individually [3,13,[24][25][26] and in the pest regime and at higher temperatures when added simultaneously [3,27]. There is no data about (i) the microstructure and (ii) the oxidation of Nb-silicide-based alloys in which Ge and Sn are added simultaneously with TMs and RMs but without Al and Cr additions.…”

Section: Alloy Design and Selectionmentioning

confidence: 99%

“…As regards the above constraints, the (a), (d), and (e) were related to the creep target and data about creep in [4,13] and references within, the (b), (d), (e), and (g) were linked with (c) and the aim to have specific strengths higher than Ni-based superalloys, and the (b), (f), and (g) were linked with oxidation resistance. The choice of Sn concentrations, and thus constraints (f) and (g), was also "guided" by literature about the effect of Sn or Ge on the oxidation behavior of Nb-silicide-based alloys [3,13,[24][25][26][27].…”

Section: Alloy Design and Selectionmentioning

confidence: 99%

“…The latter is defined as MACSi = C max Si − C min Si where C max Si and C min Si , respectively are the maximum and minimum Si concentrations in the cast alloy [26,27]. The MACSi values were 5.6 and 4.9 at.% for the alloys JZ1 and KZ2, respectively.…”

Section: Macrosegregation Of Si (Macsi) Existed In Both Alloysmentioning

confidence: 99%

“…Pest oxidation at intermediate temperatures (600-900 • C) is suppressed by the synergy of Al, Cr, Si, and Ti with B, Ge, or Sn [3,13]. Spallation of oxide scales formed at high temperatures is a common phenomenon [22,[24][25][26]. However, scale spallation was prevented in a Nb-silicide-based alloy when Ge and Sn were added simultaneously with Al, Cr, Hf, Si, and Ti [27].…”

mentioning

confidence: 99%

“…Elements in RCCAs are the group IV, V, and VI TMs and RMs and sometimes there are additions of Al and/or Si (and Co or Ni). The same elements are used as additions in Nb-silicide-based alloys [13] with the exception of Ta, V, or Zr that have been used less frequently and Co and Ni that have not been used at all.Toughness at room temperature, oxidation in the pest regime (600-900 • C) and at high temperatures (≥1000 • C), and creep at T ≥ 1050 • C and stress (σ) in the range 50 to 300 MPa have been evaluated for Nb-silicide-based alloys [2][3][4][5]13,[18][19][20][21][22][23][24][25][26][27][28][29] and references within. Properties of the key phases in the latter alloys have also been measured [13] and references within and the effects of alloying on properties of Nb 5 Si 3 have been studied [13] and references within.…”

mentioning

confidence: 99%

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On the Microstructure and Properties of Nb-12Ti-18Si-6Ta-2.5W-1Hf (at.%) Silicide-Based Alloys with Ge and Sn Additions

2020

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In this paper two Nb-silicide-based alloys with nominal compositions (at.%) Nb-12Ti-18Si-6Ta-2.5W-1Hf-2Sn-2Ge (JZ1) and Nb-12Ti-18Si-6Ta-2.5W-1Hf-5Sn-5Ge (JZ2) were studied. The alloys were designed using the alloy design methodology NICE to meet specific research objectives. The cast microstructures of both alloys were sensitive to solidification conditions. There was macro-segregation of Si in JZ1 and JZ2. In both alloys the βNb5Si3 was the primary phase and the Nbss was stable. The A15-Nb3X (X = Ge,Si,Sn) was stable only in JZ2. The Nbss+βNb5Si3 eutectic in both alloys was not stable as was the Nb3Si silicide that formed only in JZ1. At 800 °C both alloys followed linear oxidation kinetics and were vulnerable to pesting. At 1200 °C both alloys exhibited parabolic oxidation kinetics in the early stages and linear kinetics at longer times. The adhesion of the scale that formed on JZ2 at 1200 °C and consisted of Nb and Ti-rich oxides, silica and HfO2 was better than that of JZ1. The microstructure of JZ2 was contaminated by oxygen to a depth of about 200 μm. There was no Ge or Sn present in the scale. The substrate below the scale was richer in Ge and Sn where the NbGe2, Nb5(Si1-xGex)3, W-rich Nb5(Si1-xGex)3, and A15-Nb3X compounds (X = Ge,Si,Sn) were formed in JZ2. The better oxidation behavior of JZ2 compared with JZ1 correlated well with the decrease in VEC and increase in δ parameter values, in agreement with NICE. For both alloys the experimental data for Si macrosegregation, vol.% Nbss, chemical composition of Nbss and Nb5Si3, and weight gains at 800 and 1200 °C was compared with the calculations (predictions) of NICE. The agreement was very good. The calculated creep rates of both alloys at 1200 °C and 170 MPa were lower than that of the Ni-based superalloy CMSX-4 for the same conditions but higher than 10−7 s−1.

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