Jan Sieniawski

The effect of microstructure on the mechanical properties of two-phase titanium alloys

Abstract This paper presents the results of investigations of the microstructure and mechanical properties of two-phase α+β titanium alloys after different heat treatment. The influence of the morphology of lamellar microstructure and phase composition on the tensile properties and fracture toughness of the alloys was studied. Static tensile, hardness and fracture toughness tests and microstructure investigations were performed. It was noticed that the cooling rate from the β-phase range and ageing conditions had an effect on the microstructure parameters, volume fraction and chemical composition of the β-phase, and has a significant effect on the mechanical properties of the alloys tested.

Development of the microstructure and fatigue strength of two phase titanium alloys in the processes of forging and heat treatment

Abstract The paper reports results of the studies on the influence of deformation degree and temperature in the die forging process and annealing temperature on the fatigue strength of forgings made of two phase martensitic titanium alloys Ti–6Al–4V and Ti–6Al–2Mo–2Cr. Dilatometric and metallographic studies have been carried out along with X-ray phase analysis and fatigue tests. The influence of the phase composition and microstructure obtained after cooling with different rates on the fatigue strength have been determined.

Modeling of Directional Solidification of Columnar Grain Structure in CMSX-4 Nickel-Based Superalloy Castings

The paper presents the analysis of numerical simulation of the Bridgman directional solidification process performed on CMSX-4 rods. The numerical simulation was studied applying the ProCAST software. The constitutive law parameters of the normal Gaussian distribution were used to describe the nucleation process. The coefficients of the equation were determined and used to calculate the growth rate of dendrite tip. The analysis of the as-cast microstructure was carried out with the use of Aphelion software in order to determine the average area of grains and their quantity. The experimental verification of both nucleation and grain growth coefficients used for the simulation of the directional solidification process confirmed that the model was correct and described well the investigated process of directional solidification using the Bridgman method.

Rapid prototyping in manufacturing of core models of aircraft engine blades

Purpose – The purpose of this paper is to present the advantages of computer-aided design/rapid prototyping (CAD/RP) usage in designing and manufacturing of the core models used for precise casting with direct and single solidification of aircraft engine turbine blade cores. Design/methodology/approach – The process of modelling three-dimensional CAD geometry of research blade in relation to the model of the core was presented with different wax types used in the RP technique. Findings – The geometry of the blade model has been designed in a way which allows making a silicon mould on the basis of a base prototype in the process of rapid tooling (RP/RT). Filing by different wax types was investigated in mean of the impact on filling accuracy of the mould cavity. Originality/value – The resulting models were used to make ceramic moulds and carry further work on the development of casting technology in the process of directional solidification and single crystal solidification of core blades of aircraft engines.

Correlation between SEM and X-Ray Diffraction Imaging of Defect Structure in Single-Crystal Ni-Based Superalloy

In the work the single-crystalline alloy CMSX-4 was studied. The main aim of the study was an attempt to find correlations between images of X-Ray topography, X-ray diffraction maps of lattice parameter and misorientation angle and Scanning Electron Microscopy (SEM) images obtained by back-scattered electron (BSE) technique. Topography images were obtained by Auleytner method with wide beam. Diffractometer provided by EFG company was used for obtaining orientation and lattice parameter maps. Material for research was produced in Research and Development Laboratory for Aerospace Materials of Rzeszów University of Technology. Casts were obtained in ALD furnace by the Bridgman technique. It was found that X-ray topograms were correlated with SEM images of microstructures as well as with orientation and lattice parameter maps. X-Ray topograms showed high contrast bands which corresponded to dendrite arms. There was a correlation between low angle boundary and lattice parameter map.

Microstructure and oxidation behaviour investigation of rhodium modified aluminide coating deposited on CMSX 4 superalloy

The CMSX 4 superalloy was coated with rhodium 0.5‐μm thick layer and next aluminized by the CVD method. The coating consisted of two layers: the additive and the interdiffusion one. The outward diffusion of nickel from the substrate turned out to be a coating growth dominating factor. The additive layer consists of the β‐NiAl phase, whereas the interdiffusion layer consists of the β‐NiAl phase with precipitates of σ and μ phases. Rhodium has dissolved in the coating up to the same level in the matrix and in the precipitates. The oxidation test proved that the rhodium modified aluminide coating showed about twice better oxidation resistance than the nonmodified one.

X-Ray Topography Study of the Nickel Superalloy CMSX-4 Single Crystals

The paper attempts to determine structural perfection of monocrystalline nickel superalloys using X-ray topography. Monocrystalline bars and turbine blades were manufactured in an ALD Vacuum Technologies furnace using the Bridgman method. Pulling out rates typical for CMSX-4 nickel superalloys were used. It has been found that in the case of monocrystalline bars the structural perfection determined based on X-ray topograms does not depend on the distance from the selector. Instead, for blades the structural perfection significantly decreases with increasing distance from the selector.

The Effect of Zirconium Addition on the Oxidation Resistance of Aluminide Coatings

Nickel, Mar M247, and Mar M200 superalloys were coated with zirconium-doped aluminide deposited by the chemical vapor deposition method. All coatings consisted of two layers: an additive one, comprising of the β-NiAl phase and the interdiffusion one. The interdiffusion layer on pure nickel consisted of the γ′-Ni3Al phase and β-NiAl phase on superalloys. Precipitations of zirconium-rich particles were found near the coating’s surface and at the interface between the additive and the interdiffusion layer. Zirconium doping of aluminide coating improved the oxidation resistance of aluminide coatings deposited both on the nickel substrate and on the Mar M200 superalloy. Precipitations of ZrO2 embedded by the Al2O3 oxide were formed during oxidation. It seems that the ZrO2 oxide increases adhesion of the Al2O3 oxide to the coating and decreases the propensity of the Al2O3 oxide rumpling and spalling.

The Unidirectional Crystallization of Metals and Alloys (Turbine Blades)

Abstract In the work, ceramics (zirconium silicate, aluminosilicates, mullite, zirconium dioxide), waxes, and binders used in investment casting of nickel-based superalloys have been characterized. Additionally, methodology of wax model pattern and ceramic molds for investment casting process have been discussed. The manufacturing methods (Bridgman, liquid metal cooling (LMC), gas cooling casting (GCC)) of single crystal and directionally solidified (DS) castings (mainly of aircraft engine and gas turbine blades) from nickel-based superalloys were presented. Moreover, the geometry of starter and selector in single crystal (SC) castings has been characterized. In the work, chemical composition of nickel-based superalloys (DS and SC), heat treatment technology, and test methods (macro-and microstructure, mechanical properties, crystalline perfection by Laue method, EBSD, and diffractometry) of nickel-based superalloys casting were shown and the principles of modeling the process of directional solidification (nucleation and grain growth) by finite element method (FEM) method has been described.

Phase Transformations and Characterization of α + β Titanium Alloys

Phase transformations the effects of which are used in manufacturing processes of structural elements made of two-phase titanium alloys are discussed in the chapter. In order to describe the effect of microstructure on mechanical properties of titanium alloys, phase constituents of microstructure and possible phase compositions too were characterized. Authors presented methods of developing of microstructure and analyzed factors determining technological properties of titanium alloys, like hot plasticity (including superplasticity).