Recently, deep cryogenic treatment is performed to improve the mechanical responses (wear, hardness, fatigue, and thermal conductivity) of various steel components. Researchers have tried to evaluate the eco-friendly and nontoxic process to optimize the parameters. Cold-shearing punches used to manufacture various holes that undergo severe impact loading and wear in the metal forming process. This study concerns the effect of soaking time (24 hr, 36 hr) at liquid nitrogen temperature (−145 °C) during the deep cryogenic treatment on the microstructural changes which are carbide distribution and retained austenite percentage of AISI D3 tool steel punches. It was shown that the deep cryogenic treatment reduces retained austenite and enhanced uniform distribution of carbide particles. It is concluded that for significantly improved punch life and performance, it is an advisable application of 36 hr deep cryogenic treatment.
It is well known that cryogenic treatment is used to improve the mechanical properties of a material. Consequently, the use of cryogenic treatment has grown beyond its successful application on tool steels. In this research, the effects of cryogenic treatment on the corrosion of AISI D3 steel in 3.5% NaCl solution were examined by electrochemical impedance spectroscopy (EIS). The surface structure of the AISI D3 steel was examined by scanning electron microscopy (SEM) after the EIS investigations. Results clearly indicated that the pre-treatment of the steel was responsible for a significant effect on corrosion. The heat treatment process prior to the cryogenic treatment and the tempering process after were shown to decrease corrosion resistance. Uygur et al. 570 Materials Research
Keywords: corrosion, cryogenic treatment, electrochemical impedance spectroscopy, AISI D3 steel
Material and MethodsElectrochemical measurements were carried out in a three-electrode type cell with separate compartments for the reference electrode (Ag/AgCl), the counter (Pt) and the working (AISI D3 steel) electrodes having an area of 0.5 cm². The surfaces of the working electrode were prepared by grinding with 400-1800 grade abrasive paper, rinsing with distilled water and then degreasing with acetone. During the measurements, the solution was stirred with a magnetic stirrer (500 rot/min). The composition of AISI D3 steel is given in Table 1.Four types of uncoated AISI D3 steel samples were used: conventionally heat treated, 24 h cryogenically treated, 36 h cryogenically treated and 36 h cryogenically treated and then 2 h tempered at 150 °C. The cryogenic treatment for the AISI D3 samples was achieved by gradually lowering them from room temperature to -145 °C at the cooling rate of about 5 °C/min and holding at this cryogenic temperature for 24 h or 36 h, then gradually bringing them back to room temperature at the heating rate of 5 °C/min. The scheme in Figure 1 shows the various treatments and treatment cycles applied to the samples. The tempering of the AISI D3 steel was performed in a muffle furnace with the capacity of 9 kW, 380 V and 1200 °C.After the AISI D3 steel samples were prepared as described above (Figure 1), their corrosion behaviour in a 3.5% NaCl medium was then examined. For the investigation, abridged labels were used for the AISI D3 steel sample qualifications (Table 2). Thus, the following discussion will be made easier by referring to these codes.
Electrochemical measurementsThe electrochemical impedance spectroscopy (EIS) measurements were performed using a Reference 600 Gamry Potentiostat/Galvanostat/ZRA (M/S Gamry Instruments, USA). Before EIS measurement, each sample was immersed in the corrosion cell and allowed to stabilise for 2 h. The EIS studies were performed by imposing a sinusoidal voltage of 10 mV amplitude as the open circuit potential of the working electrode. The frequency was varied between 100 kHz and 1 mHz.
Surface morphology studiesAfter the EIS measurements, surface analyses of the worki...
In this study, not only the effects of cryogenic processing on the wear of AISI M2 punches but also the effects of punch wear on the hole edge geometry of DIN EN 10111-98 sheet metal control arm parts were investigated. The hole geometry changes are generally associated with punch wear and process parameters. Piercing operations were performed using eccentric press on 2.5-mm-thick sheet metal control arm parts with circular and slot AISI M2 tool steel punches. The punches were traditionally heat treated. The others were cryogenically treated at −145°C in addition to the conventional heat treatment. Weight losses were measured for punch wear assessments; furthermore, SEM and OM images were analyzed. The hole edge geometries of the selected parts were measured with a contour measuring machine in the specified number of blanks. So, no damage was done to the products for measurements. The cryogenic process resulted in a significantly low amount of retained austenite and caused uniformly distributed thin carbide precipitates. Reduction of retained austenite and formation of fine carbide particles led to increase in hardness values. It was found that untreated circular punch wear weight losses were approximately 40% higher than those of cryogenically treated samples. The untreated slot punch change rate was about 106% higher than that of the cryogenically treated samples. The wear process during the punching was faster and greater for the untreated punches. Fatigue microcracks were more common at the cutting edge of the untreated punches. However, abrasive wear was generally observed in cryogenically treated punches. The edge geometry values in the circular holes were at least two times higher than those in the slot holes of untreated samples. At the end of the industrial piercing process, it was determined that the M2 tool steel punch wear rates were decreased by cryogenic treatment, and the size changes of the hole geometry of the punches of the DIN EN 10111-98 control arm parts were more economic and with a better quality.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.