Instytut Podstawowych Problemów Techniki
Polskiej Akademii Nauk

Partnerzy

Denis J. Politis

Imperial College London (GB)

Ostatnie publikacje
1.  Kukla D., Kopeć M., Kowalewski Z.L., Politis D.J., Jóźwiak S., Senderowski C., Thermal barrier stability and wear behavior of CVD deposited aluminide coatings for MAR 247 nickel superalloy, Materials, ISSN: 1996-1944, DOI: 10.3390/ma13173863, Vol.13, No.17, pp.3863-1-11, 2020

Streszczenie:
In this paper, aluminide coatings of various thicknesses and microstructural uniformity obtained using chemical vapor deposition (CVD) were studied in detail. The optimized CVD process parameters of 1040 °C for 12 h in a protective hydrogen atmosphere enabled the production of high density and porosity-free aluminide coatings. These coatings were characterized by beneficial mechanical features including thermal stability, wear resistance and good adhesion strength to MAR 247 nickel superalloy substrate. The microstructure of the coating was characterized through scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis. Mechanical properties and wear resistance of aluminide coatings were examined using microhardness, scratch test and standardized wear tests, respectively. Intermetallic phases from the Ni-Al system at specific thicknesses (20-30 µm), and the chemical and phase composition were successfully evaluated at optimized CVD process parameters. The optimization of the CVD process was verified to offer high performance coating properties including improved heat, adhesion and abrasion resistance.

Słowa kluczowe:
chemical vapor deposition, nickel alloys, coatings, X-ray analysis

Afiliacje autorów:
Kukla D. - IPPT PAN
Kopeć M. - IPPT PAN
Kowalewski Z.L. - IPPT PAN
Politis D.J. - Imperial College London (GB)
Jóźwiak S. - inna afiliacja
Senderowski C. - inna afiliacja
140p.
2.  Wang K., Kopeć M., Chang S., Qu B., Liu J., Politis D.J., Wang L., Liu G., Enhanced formability and forming efficiency for two-phase titanium alloys by fast light alloys stamping technology (FAST), Materials & Design, ISSN: 0264-1275, DOI: 10.1016/j.matdes.2020.108948, pp.1-25, 2020

Streszczenie:
During hot stamping of titanium alloys, insufficient forming temperatures result in limited material formability, whereas temperatures approaching the β phase transus also result in reduced formability due to phase transformation, grain coarsening and oxidation during the long-time heating. To solve this problem, Fast light Alloys Stamping Technology (FAST) is proposed in this paper, where fast heating is employed. Effects of heating parameters on the formability and post-form strength were studied by tensile tests. Forming of a wing stiffener was performed to validate this new process. Results show that microstructure of TC4 alloy after fast heating was in nonequilibrium state, which could enhance ductility significantly compared with the equilibrium state. When TC4 alloy was first heated to 950 °C with heating rate of 100 °C/s and then cooled to 700 °C, the elongation at 700 °C was more than 3 times that of a slow heating rate with soaking. Nano-scaled martensite with high dislocation density transformed from β phase was observed under fast heating condition. A complex shaped wing stiffener was successfully formed from TC4 titanium alloy in less than 70 s including heating, transfer and forming, and the post-form strength was almost the same with the initial blank.

Słowa kluczowe:
titanium alloys, fast heating, hot stamping, formability, post-form strength

Afiliacje autorów:
Wang K. - Imperial College London (GB)
Kopeć M. - IPPT PAN
Chang S. - Harbin Institiute of Technology (CN)
Qu B. - Harbin Institiute of Technology (CN)
Liu J. - Imperial College London (GB)
Politis D.J. - Imperial College London (GB)
Wang L. - Imperial College London (GB)
Liu G. - Harbin Institiute of Technology (CN)
140p.
3.  Kopeć M., Wang K., Politis D.J., Wang Y., Wang L., Lin J., Formability and microstructure evolution mechanisms of Ti6Al4V alloy during a novel hot stamping process, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2018.02.038, Vol.719, pp.72-81, 2018

Streszczenie:
A novel hot stamping process for Ti6Al4V alloy using cold forming tools and a hot blank was presented in this paper. The formability of the material was studied through uniaxial tensile tests at temperatures ranging from 600 to 900 °C and strain rates ranging from 0.1 to 5 s-1. An elongation ranging from 30% to 60% could be achieved at temperatures ranging from 750 to 900°C respectively. The main microstructure evolution mechanisms varied with the deformation temperature, including recovery, phase transformation and recrystallization. The hardness of the material after deformation first decreased with the temperature due to recovery, and subsequently increased mainly due to the phase transformation. During the hot stamping tests, qualified parts could be formed successfully at heating temperatures ranging from 750 to 850°C. The forming failed at lower temperatures due to the limited ductility of the material. At temperatures higher than 900°C, extensive phase transformation of α to β occurred during the heating. During the transfer and forming, the temperature dropped significantly which led to the formation of transformed β, reduction of the formability and subsequent failure. The post-form hardness distribution demonstrated the same tendency as that after uniaxial tensile tests.

Słowa kluczowe:
titanium alloys, Ti6Al4V, hot stamping, microstructure

Afiliacje autorów:
Kopeć M. - IPPT PAN
Wang K. - Imperial College London (GB)
Politis D.J. - Imperial College London (GB)
Wang Y. - Beijing Aeronautical Manufacturing Technology Research Institute (CN)
Wang L. - Imperial College London (GB)
Lin J. - Imperial College London (GB)
35p.

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