A hypoeutectoid steel was austenitized at 840 °C for one hour and cooled at two rates. Examination by optical and scanning electron microscopy showed a change in the pearlite microstructure. Cooling in air as compared to furnace cooling reduced the pearlite interlamellar spacing and increased the hardness. The slower cooling resulted in a lower tensile strength, higher tensile elongation, and different fracture appearance.

Ti-6Al-4V alloy is characterized to be sensitive to heat treatment and deformation. This paper focuses on microstructural evolution and variation in mechanical properties with respect to the deformation and change in the heat treatment cycle. Different heat treatment cycles such as mill annealing, solution treatment and beta solution treatment followed by annealing were carried out on deformed and undeformed Ti-6Al-4V samples. Heat treated samples were studied using optical and scanning electron microscopy. Also different mechanical tests (i.e. tensile test, fracture toughness test) were conducted and results were analyzed. Large variation in mechanical properties and microstructures were found out with different heat treatment cycles. Fracture toughness was found to be high for beta solution treatment samples than the mill annealed and solution treated samples and the reason for the same has been analyzed.

Temperature Processing Inc. has offered merchant heat treating in the northern NJ town of North Arlington for over 60 years. Their 10,000 sq ft facility, expanded in 1998, offers broad thermal processing capability in a compact plant. Diverse services offered include annealing, tempering, bright hardening, ageing and nitriding.

Nitrogen (N 2 ) atmospheres with different, not always optimized levels of reducing and carburizing gases are often used to prevent decarburizing and oxidation of steel parts during annealing in continuous furnaces. The type and concentration of these additives in N 2 should correlate to the extent of air leakage into furnace, entrainment of air with loaded parts, steel composition, and complex reaction kinetics in the gradients of oxygen (O 2 ) and temperature existing between the entrance and hot zones of the furnace. This study explores the effect of small, 0.1 vol.% - 0.4 vol.% propane (C 3 H 8 ) additions on composition of air-contaminated N 2 atmosphere in the temperature range of 500°C - 860°C. Microstructures are presented for AISI 1045 steel exposed to the atmospheres produced. Atmosphere compositions compared include those produced by a new type of plasma activated, in-situ reformer for N 2 -diluted C 3 H 8 . The latter method extends the atmosphere protection to the lower range of annealing temperatures. Present results may assist heat treaters in optimizing their neutral hardening operations.

This paper presents the results of an experimental investigation of the effect of three types of post-heat treatments: 1) solution treatment and aging, 2) stress relieving, and 3) annealing on the corrosion behavior of Ti-6Al-4V fabricated via direct metal laser sintering (DMLS). The microstructure and phase evolution as affected by heat treatment temperature were examined through scanning electron microscopy and via x-ray diffraction. The Vicker’s microhardness, as it was affected by various heat treatments, was compared. The corrosion behavior of the specimens was measured electrochemically in simulated body fluid at 37°C. It was found that the nonequilibrium α’ phase with a small amount of β nuclei was formed in the as-fabricated sample. Heat treatments allow the formation of the β phase and the agglomeration of β precipitates to occur at elevated temperatures. Transformed β phase with various morphologies was observed as a result of the heat treatments. Different degrees of improvement in the corrosion resistance were observed in the solution-treated and aged samples, 650 °C stress relieved, and annealed samples.

Case carburizing grade steel forgings are often normalized or iso-annealed to improve machinability. The aim here is to get a uniform ferrite-pearlite microstructure and controlled, uniform hardness. Since during forging material is above austenitizing temperature, controlled slow cooling after trimming can give similar results. In this work, the effect of forging temperature and cooling rate at different stages on microstructure is studied. Further the effect of this process on machinability and distortion behavior of gears during case carburizing is studied. It was observed that the controlled cooled gear blanks had coarse grain size resulting in superior machinability, and no change was observed in the distortion behavior of the gears during case carburizing.

Since the invention of the vacuum furnace in the 1950s and up until the 1970s, its primary use was for annealing aerospace components. In the 1980s, vacuum equipment began to be used for heat treating tools and dies. By the 1990s, the need for faster quenching of high-alloy steels led to the development of vacuum furnaces capable of quenching at pressures up to 20 bar. Prior to this, only certain hot-work steels and a few tool steels with small cross-sections could be satisfactorily hardened in vacuum furnaces. Today, it is understood that simply increasing quenching pressure does not necessarily yield optimal results. Modern vacuum furnace technology allows for the precise design of the entire quench curve to maximize material performance while minimizing distortion. Continuous advancements and new concepts, such as multi-directional cooling systems, separate quenching chambers, and integrated cryo-cooling systems, have led to oxidation-free and low-distortion vacuum heat treatment for a wide range of parts and materials. This paper demonstrates how modern vacuum furnace designs and processes can improve quenching and cooling. It includes proven heat treatment results and examples from the international tool and die industry, which has been utilizing this technology over the past 25 years.

The 2524 aluminum alloy was cold rolled to 70% reduction and then annealed at 500? for 0.5h in an air furnace with a heating rate of 5?/min and in a salt bath with a heating rate of 75?/s, respectively. The effect of heating rate on the microstructure, tensile properties and fatigue crack growth (FCG) rate of the alloy was investigated. The microstructure and mechanical properties of the alloy were studied by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical microscopy (OM), tensile and FCG rate tests. In the case of slow heating the alloy exhibited a coarse elongated grain structure (~75μm), while a fine equiaxed grain structure (~13μm) was obtained in the case of rapid heating. The sheet annealed with rapid heating has slightly higher tensile strength and yield strength, but a slightly lower elongation than the sheet annealed with slow heating. The FCG rate of the sheet annealed with slow heating is 20% lower than the sheet annealed with rapid heating.

Atmospheric pressure carburizing and neutral carbon potential annealing in nitrogen containing small additions of hydrocarbon gases can offer cost and steel surface quality alternatives to the comparable, endothermic atmosphere or vacuum operations. An experimental program was conducted for refining real-time process control methods in carburizing of AISI 8620 steel under N 2 -C 3 H 8 blends containing from 1 to 4 vol% of propane at 900°C and 930°C. Multiple types of gas analyzers were used to monitor residual concentrations of H 2 , CO, CO 2 , H 2 O, O 2 , CH 4 , C 3 H 8 , and other hydrocarbons inside furnace. A modified shim stock technique and the conventional oxygen probe (mV) were additionally evaluated for correlation with gas analysis and diffusional modeling using measured carbon mass flux values (g/cm 2 /s). Results of this evaluation work are presented.