Transforming foundation industries ISCF challenge - 2nd deep dive workshop

The workshop was intended to scope key areas of interest from the industrial and academic community for cross-sector collaboration and to inform targetting of funding calls for the Transforming Foundation Industries Challenge (up to £66M available) of the Industrial Strategy Challenge Fund (ISCF). The morning consisted of an introduction from Dr Robert Quarshie, an overview of the ISCF challenges from Dr Ben Walsh (Lead Technologist in Advanced Materials at Innovate UK) and then short summary presentations from representatives of the 6 foundation industries, Ceramics, Cements, Chemicals, Glass, Metals and Paper. The afternoon consisted of break out sessions based around 7 tables of 11 people with a facilitator for each group. The first session was an initial brain storming focused on the key challenges affecting the foundation industries and opportunities for cross-sector collaborations, followed by a feedback session. After the feedback, the groups were asked to prioritise three key challenges. The common themes identified across the 7 tables were, (i) Energy efficiency, (ii) Digitalisation, (iii) Efficient and sustainable use of materials including reuse of waste and (iv) Skill shortages. Attendees were then asked to vote on how important each challenge/opportunity was and when these would be expected to benefit the industries. The outputs from the day will be collated into a report to be circulated at a later date

High-temperature microstructural evolution and quantification for alloys IN740 and IN740H: comparative study

In ultra-supercritical power plants, Ni-base alloys are candidate materials for long-term, high-temperature applications, operating at temperatures and pressures as high as 750°C and 35 MPa. Alloy IN740 and its modification, alloy IN740H, are considered for such applications. Their microstructural evolution, at 750°C for times ranging between 3000 and 5000 hours, has been investigated by means of scanning electron microscopy, electron back-scattered diffraction, energy dispersive X-ray analysis and phase quantification. All phases were identified and quantified allowing comparison between the two microstructures, their evolution and stability. Particular attention was paid to γ′, η and G phases. The results are used within a broader investigation aimed at improving and further developing a predictive creep model based on continuous damage mechanics

Synthesis and structural characterisation of new ettringite and thaumasite type phases: Ca6[Ga(OH)6•12H2O]2(SO4)3•2H2O and Ca6[M(OH)6•12H2O]2(SO4)2(CO3)2, M = Mn, Sn

Investigations into the formation of new ettringite-type phases with a range of trivalent and tetravalent cations were carried out to further study the potential this structure type has to incorporate cations covering a range of ionic radii (0.53–0.69 Å). We report the synthesis and structural characterisation of a new ettringite-type phase, Ca6[Ga(OH)6•12H2O]2(SO4)3•2H2O, which was indexed in space group P31c with the unit cell parameters a = 11.202(2) Å, c = 21.797(3) Å and two new thaumasite-type phases Ca6[M(OH)6•12H2O]2(SO4)2(CO3)2, M = Mn, Sn which were indexed in space group P63 with the unit cell parameters a = 11.071(5) Å, c = 21.156(8) Å and a = 11.066(1) Å, c = 22.420(1) Å respectively. These new phases show the versatility of the ettringite family of structures to tolerate a large range of cation sizes on the octahedral M site and highlights the preference of tetravalent cations to crystallise with the thaumasite structure over the ettringite structure

Modelling of creep and fracture properties of nickel based alloys

This paper reviews the differences between two nickel based alloys, Alloy 740 and Alloy 740H. Microstructural evolution models are used to forecast the changes in volume fraction and interparticle spacing of both grain boundary and intra-granular precipitates in the alloys. These data are then employed in continuum damage mechanics models to forecast creep curves, and in fracture mechanics models to forecast Charpy impact energies/energy. The results reveal the key microstructural features that control secondary and tertiary creep rate as well as the time dependence of Charpy impact energy after high temperature exposure

Evolution of sigma phase in 321 grade austenitic stainless steel parent and weld metal with duplex microstructure

Samples of 321 stainless steel from both the parent and welded section of a thin section tube were subjected to accelerated ageing to simulate long term service conditions in an advanced gas cooled reactor (AGR) power plant. The initial condition of the parent metal showed a duplex microstructure with approximately 50% ferrite and 50% austenite. The weld metal showed three distinct matrix phases, austenite, delta ferrite and ferrite. This result was surprising as the initial condition of the parent metal was expected to be fully austenitic and austenite+delta ferrite in the weldment. The intermetallic sigma phase formed during the accelerated ageing was imaged using ion beam induced secondary electrons then measured using computer software which gave the particle size as a function of aging time. The measurements were used to plot particle size, area coverage against aging time and minimum particle spacing for the parent metal. During aging the amount of ferrite in the parent metal actually increased from ∼50 to ∼80% after aging for 15 000 h at 750°C. Sigma has been observed to form on the austenite/ferrite boundaries as they may provide new nucleation sites for sigma phase precipitation. This has resulted in small sigma phase particles forming on the austenite/ferrite boundaries in the parent metal as the ferrite transforms from the austenite

Analysis of deposits formed during biomass co-firing on 15Mo3 under different gas and temperature conditions

This paper reports on the analysis of fly ash and oxides on 15Mo3 after the co-firing of eucalyptus and a Russian coal at various temperatures and gas conditions for 50 hours. The loose deposits present have been characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Results show that under reducing conditions KCl deposition is increased and a variation in oxide scale composition is observed. Complex silicates, often present as spheres are imaged through SEM

The microstructural development of type 321 Austenitic Stainless Steel with long term ageing

Austenitic stainless steel is important in the power generation industry where it is expected to be in service at high temperatures for extended periods of time. Work carried out on the microstructural development of two 321 stainless steel samples has shown that there are complex phase changes that can take place in this alloy. Although the alloy is expected to be fully austenitic at room temperature there is a fraction of ferrite present in the as-received materials. High temperature XRD has shown that this ferrite phase can be dissolved at temperatures between 800 and 900°C but precipitates on cooling at temperatures below 200°C. Due to the low temperature of formation, similarities in chemistry and orientations relationships indicate that the ferrite is forming in a displacive manor from the austenite grains. Thermal ageing at 750°C has been carried out up to times of 15,000 hours and the microstructural changes quantified. The fraction of sigma phase and ferrite increases with ageing time with a corresponding decrease in austenite fraction. This change in the microstructure is postulated to be caused by the changes in the matrix chemistry due to the formation of second phases particles

Characterisation, analysis and comparison of multiple biomass fuels used in co-firing trials

The co-firing of biomass and coal is one method proposed for the reduction of CO2 emissions. This paper compares synthetic laboratory ash of hemp, coal and eucalyptus and their co-ashed blends with deposits formed during the co-combustion of hemp and coal and eucalyptus and coal. Results show that whilst the results are not in complete agreement a trend towards the formation of Ca-silicates, Ca-Mg silicates and K-Al-Silicates at high temperatures is present in both laboratory ashed samples. The morphology of the particles formed through the different methods differs with larger spherical agglomerates present in the deposits

Characterisation of microstructure and creep properties of alloy 617 for high-temperature applications

Current energy drivers are pushing research in power generation materials towards improved efficiency and improved environmental impact. In the context of new generation ultra-supercritical (USC) power plant, this is represented by increased efficiency, service temperature reaching 750. °C, pressures in the range of 35-37.5. MPa and associated carbon capture technology. Ni base alloys are primary candidate materials for long term high temperature applications such as boilers. The transition from their current applications, which have required lower exposure times and milder corrosive environments, requires the investigation of their microstructural evolution as a function of thermo-mechanical treatment and simulated service conditions, coupled with modelling activities that are able to forecast such microstructural changes. The lack of widespread microstructural data in this context for most nickel base alloys makes this type of investigation necessary and novel. Alloy INCONEL 617 is one of the Ni-base candidate materials. The microstructures of four specimens of this material crept at temperatures in the 650-750. °C range for up to 20,000. h have been characterised and quantified. Grain structure, precipitate type and location, precipitate volume fraction, size and inter-particle spacing have been determined. The data obtained are used both as input for and validation of a microstructurally-based CDM model for forecasting creep properties

Analysis of ferrite formed in 321 grade austenitic stainless steel

A significant fraction of ferrite has been identified in a 321 grade austenitic stainless steel in the solution heat treated condition. The microstructures were analysed using electron backscatter diffraction, energy dispersive X-ray spectroscopy and X-ray diffraction (XRD) and the stability of the ferrite investigated using heat treatments in a tube furnace, dilatometry and high temperature XRD. The ferrite dissolved ,800uC, then formed again on cooling at temperatures under 200uC. Thermodynamic predictions showed a significant ferrite content at room temperature under equilibrium conditions, and the DeLong diagrams predict an austenitezmartensite microstructure in the cast condition. Sensitivity analysis on the DeLong diagram has shown that the nitrogen content had a large effect on the austenite stability. The instability of the austenite and the subsequent transformation to ferrite on cooling can be attributed to low nitrogen content measured in the as received material. It was found that thermal aging of the material caused further transformation of austenite to ferrite as well as the formation of sigma phase that appears higher in nitrogen than the matrix phases. The diffusion of nitrogen into sigma phase may cause instability of the austenite, which could cause further transformation of austenite to ferrite on cooling from the aging temperature. The transformation of austenite to ferrite is known to be accompanied by an increase in volume, which may be of relevance to components made with tight dimensional tolerances