Low-pressure Accessible Gas-quenching for Absolute Methylammonium-free Perovskite Solar Cells

Gas-quenching is a promising technique for the up-scalable fabrication of metal halide perovskite solar cells (PSCs). However, it has been challenging to produce high-quality gas-quenched perovskite film without the use...

Influence of Combined Mechanical Processes on Tribological Properties of Tool Steels Vanadis 8 and Vancron 40 With a Similar Hardness

Surface integrity is important factor for components exposed to wear, like cold working tools, which need to possess high hardness combined with high wear resistance. Surface treatments such as grinding, hard turning, and hard turning with slide burnishing have been developed for its improvement. Vancron 40 and Vanadis 8 tool steels, of different chemical composition and different types and amounts of carbides, were now investigated. Heat treatment was carried out in vacuum furnaces with gas quenching to hardness of Vancron 64 ± 1 HRC and of Vanadis 65 ± 1 HRC. 3D topography, optical and scanning electron microscopy, X-ray diffraction and ball-on-disc tribological tests against Al2O3 and 100Cr6 balls as counterparts were used to examine wear and friction. For both steels, the lowest values of dynamic frictions and wear rates against Al2O3 counterbodies were achieved after sequential process of hard turning with slide burnishing with a burnishing force of 180 N. For alumina balls, the increase of wear resistance, achieved after hard turning plus burnishing in comparison to grinding exceeds 50 and 60%, respectively for Vanadis 8 and Vancron 40 steels.

Beading Mechanism and Performance of Porous Steel Slag Microbead Abrasive

The use of the gas-quenching process for preparing porous bead slag abrasive was investigated in this paper. An X-ray diffractometer, field emission scanning electron microscope, mercury intrusion porosimetry, and stereo microscope were used to analyze the microbead forming mechanism, pore structure, acid–alkali resistance, and polishing properties of porous steel slag microbead abrasives. Results show that the porous steel slag abrasives present a mono-disperse spherical shape with a hard shell and the porosity is 42.36%. The thermodynamic fractal model indicates that the fractal dimension of the abrasive is 2.226, which shows its simple pore structure. The sample has better chemical stability in the polishing fluid than in water, acid, and alkali solution. Therefore, aluminum and copper alloys are used as substrates for polishing tests. The results indicate that the abrasives could effectively improve the quality of the workpiece surface and the polishing efficiency for aluminum alloy was higher than that for copper alloy.

Advances in Low Pressure Carburizing and High-Pressure Gas Quenching

Low Pressure Carburizing (LPC) in combination with High Pressure Gas Quenching (HPGQ) has been established as an advanced and robust technology for case hardening. The process can be applied with batches consisting of multiple layers as well as batches consisting of single-layers. The paper shows the latest progress in LPC and HPGQ for the heat treatment of automotive and aerospace components. Significant progress has been made by continuous improvements in the fields of- Fixturing / load densities,- Reduction of cycle times,- Control of distortion,- Digitalization / Automation,- Quality control and- Integration of heat treatment into the manufacturing line. Practical applications are shown for both multiple- and single layer treatment.

Gas Cooling – Is Pressure or Velocity Most Important?

This paper will debunk the age-old theory that the smaller the vacuum furnace, the faster it will quench supposition. Our study compared the cooling rates of two vacuum high pressure gas quenching furnaces - a large 10-bar vacuum furnace equipped with a 600 HP blower motor to a smaller 10-bar vacuum furnace equipped with a 300 HP motor. In comparing the critical cooling temperatures for H13 in the 1850°F to 1300°F range, the furnace that is almost three times larger in volume (110 cubic feet versus a 40 cubic feet of hot zone) cooled the same workload almost identically to its smaller counterpart. These tests prove a very important fact - that the gas flow or velocity is more meaningful than pressure (bar) when it relates to cooling rates.

Process to Minimize Distortion during High Pressure Gas Quenching Processes

A gas quenching method was developed by DANTE Solutions, in conjunction with the U.S. Army Combat Capabilities Development Command Aviation & Missile Center (DEVCOM AvMC), to control distortion in difficult to quench geometries. This new method addresses the nonuniform cooling inherent in most gas quenching processes. A prototype unit was constructed and tested with the aim of controlling the martensite formation rate uniformity in the component being quenched. With the ability of the DANTE Controlled Gas Quenching (DCGQ) unit to control the temperature of the quench gas entering the quench chamber, thermal and phase transformation gradients are significantly reduced. This reduction in gradients yields a more uniform phase transformation, resulting in reduced and predictable distortion. Being able to minimize and predict distortion during gas quenching, post heat treatment finishing operations can be reduced or eliminated, and as such, fatigue performance can be improved. This paper will discuss the prototype unit performance. Mechanical testing and metallographic analysis were also performed on Ferrium C64 alloy steel coupons and will be discussed. The results obtained showed that the slower cooling rate provided by the prototype did not alter the microstructure, hardness, strength, ductility, toughness, or residual stress of the alloy.

Applying the Masteralloy Concept for Manufacturing of Sinter Hardening PM Steel Grades

Sinter hardening is a powder metallurgy processing route that combines the sintering and the heat treating processes in one step by gas quenching the components immediately after they have left the high temperature zone of the furnace. It is both economically attractive and ecologically beneficial since it renders deoiling processes unnecessary. The slower cooling rates associated with gas compared to oil quenching however requires special alloy concepts different to those known from wrought steels. In the present study it is shown that by admixing atomized masteralloy powders consisting of suitable combinations of Mn, Cr, Si, Fe and C to base iron or pre-alloyed steel powders, sinter hardening PM steel grades can be produced that transform to martensitic microstructure at cooling rates of 2-3 K/s as typical for industrial sinter hardening. This is confirmed by CCT diagrams and hardness measurements. However, metallographic investigations are also necessary because in sintered steels, the cores of the largest base powder particles are alloyed very slowly during sintering and therefore tend to result in soft spots in the sinter hardened microstructure which are mostly not discernible in the CCT diagrams. Here, even slight pre-alloying of the base powder with Mo and/or Cr is helpful, both increasing the hardenability of the steels compared to base plain iron and avoiding soft spots in the microstructure.