Summary The highest impact toughness was exhibited

Summary of JournalThe purpose of the study was to determine the effects of different heat treatments on microstructure, wear, hardness and toughness behavior of GX 10CrNiMoNb 18-10 austenitic stainless-steel in order to find alternative usage possibilities of the alloy. This study experimentally showed that increasing grain size was observed with decreasing cooling rates of the alloy. In addition to this, there is a gradual decrease of alloy toughness with increasing cooling rates during the quenching stage of the specimens. The highest impact toughness was exhibited by the furnace cooled specimen while the lowest was of the water-cooled sample. Moreover, the furnace cooled specimen was also found to be the most wear resistant alloy with the air-cooled sample as the second most wear resistant alloy.Samples of sand mold cast GX 10CrNiMoNb 18-10 (316Cb, 1.4580) grade austenitic stainless steel –5 identical samples of Charpy notched-impact test appropriate dimensions and 5 identical samples of wear test appropriate dimensions–  were used to observe the effects of different heat treatments on the alloy of interest. For each alloy behavior test, one of the specimens served as the control sample in cast condition. The remaining four specimens were subjected to heat treatment; each with a different cooling condition. The chemical composition of the alloy was determined using Optical Emission Spectroscopy. The 4 samples were subjected to Charpy notched-impact test to measure the toughness of the samples.Wear tests were also done using a ball-on-disc tribometer under dry sliding conditions at room temperature. Subsequently, the samples were subjected to microanalysis with FEI Quanta 50 Scanning Electron Microscope with Energy Dispersive X-ray Analysis (SEM/EDX) equipment.From the SEM/EDX Analysis, the composition of the alloy has been identified and was able to see the formed niobium carbide and chromium carbide. The size of the grains and its relation to the different heat treatment procedures were also discussed. It showed that samples that were slowly cooled (furnace cooled and air cooled) formed coarser grain sizes while the ones quenched with water and oil yielded finer grain sizes.These cooling media also influence the geometry of the precipitates. Ferrite content was also determined using Schaeffler-Delong diagram and was found to be about 2%, and was later concluded that the ferrite ratio does not affect the heat treatment results. Among the samples, the one cooled in a furnace possessed the highest impact toughness while the as-cast sample showed the lowest. In the wear test, results show that the furnace cooled sample has the highest wear resistance, followed by the air cooled.Review and Evaluation Austenitic stainless steels (ASSs) are one of the common types of stainless steel that are widely used because of their high weldability and formability, 6 and also their ability to withstand very high and very low temperatures 6.  Since GX 10CrNiMoNb 18-10 is a variety of ASS, the topic is significant and interesting because there are only a few studies conducted for this alloy. 7 Also, the research helps in determining an appropriate heat treatment for such metal for it to be incredibly tough and wear resistant which can be used for industrial applications 8. The title is appropriate since it could already tell what will be tested in the experiment just by reading it. However, there are some points in the paper which need further clarification with regards to the background of the experiment, methodology, and the discussion parts. In the introduction, the concepts behind the mechanical properties of the alloy were explained well. The rationale for the addition of other alloying components such as Niobium was presented and the applications and significance of the study were stated. However, it should be necessary to do a citation to support the authors’ argument about ferrite. In the paper, the authors tell that ferrite is used to reduce the stress corrosion cracking of a material but based on further readings, increasing the amount of ferrite also increases the chance of the metal to corrosion cracking 9. In the experiment, the ferrite amount was small which made them arrive at the conclusion that it will not affect the heat treatments of the specimen, which means that the effect of the cooling rate to the resulting microstructures can be easily observed 10. Mechanisms behind the used tests as well as pertinent equations used in the experiment such as wear rate should also be presented in the introduction. The methods which the authors used for determining microstructures (SEM/EDX), determining the value for toughness (V-notch impact tests) and in measuring the wear rate (ball-on-disc tribometer) were appropriate since these tests are standard and are widely used. Since this is the first time the study was made, this could be considered as a preliminary test and a very high level of accuracy is not necessary.Inconsistencies were also found in the other parts of the paper. In the methodology, the determination of the wear rate is by weighing the amount of the sample that was lost in the dry sliding with constant force and distance. However, in the results and discussion, the units for the wear rate were in terms of volume and distance. It would have been easier if it were in mass/ distance (g/m) instead. Also, the conclusion stated that furnace has the highest ‘wear resistance’ whereas in the graphs and discussion furnace has the highest ‘wear rate’. The values were the same however these two terms have opposite meanings which would make readers confused. Overall, the presentation of the paper was okay. Though it can still be improved by rephrasing some sentences in a clearer way. Placement of tables and graphs can also be arranged in a manner which it can be seen on the same page as where it is being discussed. The shapes used in the graphs could also be replaced by smaller ones in order for it to point to a more accurate value. ConclusionIt is commendable that the possible effect of the ferrite content of the alloy was properly addressed to have no significant relationship on the toughness and wear properties and ensured that only the effects of the different cooling rates are represented by the results.  While the study has its own merits, the interpretation of the experimental results should be re-evaluated. The inclusion of more replicates per cooling condition would be beneficial to the study as to ensure that the collected data is a proper result of the desired conditions. Further proofreading of the technical paper is also advised to eliminate errors in grammar or other possible inconsistencies and improve the overall presentation.