Stainless Steel Powder Metrology - Thesis Example

? and Section # of Two mixtures of powder are used to form stainless steel alloys. Mixture one, which will be termed as “A” is 99 grams 316L 1gram of Si and the second mixture, which is termed as “B” is 95 grams of 316L, 1 gram of Si and 4 grams of Boron G683. All mixtures are pressurized at 600 MPa. 6 parts of mixture A and 7 of mixture B have been taken and processes at different temperatures in the furnace, the temperatures are 1220, 1230, 1235, 1240, 1280, and 1295o C. The report will analyze the various outcomes of the different experiments carried out under different conditions. PROCEDURE The mixtures underwent a complete procedure to obtain the results and compare them according to different standards. The procedure of the experiment is explained in detail in this part of the report. Preparation of the Mixture The powder mixture, each specimen separately, is weighed and the weight recorded. The process is initiated after the weighing. The powder is properly mixed using tubes and revolving machine. In these experiments, two different mixtures, ferrous 316L with 1 gram silicon and the same mixture with the addition of 1gm boron is used. The mixtures were then sintered and quenched under different temperature conditions. The sintering has to be discussed briefly to be understood. Sintering and Quenching The specimens prepared are pressurized at 700 MPa and made into round discs as shown in the picture below. . The specimen is heated inside a closed container, to different temperature. As recorded before, there are in total 13 specimens which are used in the experiment. Each specimen is labeled properly before any kind of experiment us conducted on it. The two mixtures samples of “A” and “B” are heated at 1220, 1230, 1235, 1240, 1280, and 1295o C respectively. Each sample was then sectioned, mounted and polished for microscopical examination. These methods are explained in detail in the following part of the report. Sectioning It is essential for maximizing the working parameters since incorrect cutting can waste small samples, which are very difficult to make. The sample with deformation should be given maximum support to un-clamp them (German, 1990). Mounting The samples are too little in size to handle the different steps of the procedure. It is essential for maximizing the working parameters. Therefore a uniform and rounded surface is given to the specimen so that the damage is prevented during grinding and polishing procedures (German, 1990). Grinding The samples are grounded to reach finer surfaces. Grinding is done under stream of water to remove any free particles that are being cut out of the sample and to minimize the eroding effect on the sample and to save its surface from rash cuts. The specimen is then dried out as there was water on it (German, 1990). Polishing It is also a very important part of the experiment. Since for the photography the best surface is required. It is done by rotating a cloth over the surface with the help of a polishing machine. A polishing liquid is also used (German, 1990). Etching The samples need to be etched as the last part of the procedure. But before etching is done, the surface has to be cleaned and free of any impurity. The samples have to be etched with a proper liquid to prevent damage. During the process, the sample is removed from the sample when the first blooms of grains are observed. After etching, the samples are washed ruinously with washing material, either water or alcohol. Warm air is then passed over it. If the material is of soft nature, it must be covered so the surface can be saved (German, 1990). Microscopic examination This is a very important process since the examination with naked eye would not reveal the required results. Special method of illumination is used between the two controlling diaphragms to enlighten the eye piece where the results can be seen and photographed (German, 1990). Recording before the Procedure The two mixtures, as said before were measured in all possible dimensions before conducting the procedure on the samples like quenching and sintering. The mixture “A” has six samples named A1, A2, A3, A4, A5 and A6. Similarly the samples of mixture B are labeled B1, B2, B3, B4, B5, B6 and B7. The initial results are shown in the table. Table for mixture “A” sample Thickness Length Width weight Volume Volume green density mm mm mm g mm^3 cm^3 g/cm^3 A1 4.88 15.28 15.29 6.9605 1140.12 1.1401 6.1051 A2 4.9 15.28 15.31 6.4602 1146.29 1.1463 5.6357 A3 4.19 15.09 15.09 6.1 954.0969 0.9541 6.3935 A4 4.2 15.1 15.1 6.3 957.642 0.9576 6.5787 A5 5.11 15.2 15.2 6.992 1180.614 1.1806 5.9223 A6 5.02 15.01 15.1 6.9911 1137.788 1.1378 6.1445 Table for mixture “B” sample Thickness Length Width weight Volume Volume green density mm mm mm g mm^3 cm^3 g/cm^3 B1 4.82 15.3 15.3 6.9927 1128.314 1.1283 6.1975 B2 5.01 15.31 15.29 6.9882 1172.79 1.1728 5.9586 B3 4.95 15.27 15.27 6.99 1154.206 1.1542 6.0561 B4 4.94 15.19 15.17 6.9917 1138.336 1.1383 6.142 B5 4.94 15.27 15.27 6.9882 1151.874 1.1519 6.0668 B6 4.94 15.2 15.19 6.9857 1140.587 1.1406 6.1247 B7 4.92 15.25 15.27 6.9802 1145.708 1.1457 6.0925 RESULTS AND ANALYSIS Some of the things that are being looked for are 1. The effect of temperature 2. The effect of boron in a similar mixture, under same experiments. The fact should be kept in mind that the boron has been added in mixture “A” sample to make it mixture “B”. Now we see the results and analyze them. The results are shown after the mixtures have undergone the heat treatment process. sample temperature Weight in the air density Hardness degree g g/cm^3       A1 1295 6.9526 6.824 65.4667 A3 1285 6.0053 6.7889 66.1333 A4 1220 6.0875 6.338 66.5333 A5 1230 6.94 6.6662 66.325 A6 1240 6.99 6.6606 66.32 sample temperature Weight in the air density Hardness   degree g g/cm^3         B1 1295 6.9335 7.9008 137.3333 B3 1285 6.9261 7.6694 139 B4 1220 6.9353 7.2242 144.4 B5 1230 6.9364 7.3636 144 B6 1240 6.9145 7.491 142.6667 B7 1235 6.9862 7.4441 142.8 Both tables for mixtures after the heating process; showing weight, density and hardness. For the first analysis about the effect of temperature, we see mixture “A”. The temperature has not brought a lot of effect on the density on any sample in a huge manner. Even if the hardness is compared of all the samples in mixture A, the raise in heat at the time of process has not varied the level of hardness in any sample. There are some differences but they are more due to the difference in size rather than anything else. Now, coming to mixture “B”, in which boron was added in minute quantity. It can be seen very clearly from the tables that the density of all the samples has jumped from the range of 6 to a value near 8 g/cm3. The effect of temperature on the hardness of boron added steel can also seen by the table at the last. It is very clear that when the temperature has been increased, the hardness goes to an average value of about 144, when compared to the average value of 66 seen in the mixture without boron (mixture A). PICTORIAL RESULTS AND ANALYSIS In this last part of the report, the photographs taken under microscopes will be shown. A1: The figure above shows mixture A1, smoother edges and rough parts. A3: The figure above shows mixture A3, the whole surface is rough, less burned because of lower temperature than A1. A4: The figure above shows mixture A4, with less rigidness due to very low temperature effect as compared to A1 and A2. A6: The picture shows the result of mixture A6 which gives a comparatively smoother surface. B1: The picture shows boron added mixture with temperature applied, shows a very smooth surface B3: The picture shows the edge of mixture B3, which depicts smoothness at high temperature. B4: the picture shows the edge of mixture B4, which was exposed to the lowest temperature, hence the most abrasive surface compare to B1 and B3. The picture on the left shows mixture B6, with a lot of surface cracks and the picture on the right shows B7, with the smoothest surfaces of all. This means that the best temperature to produce the alloy is 1240 degree Celsius. POWDER METALLURGY Powder metallurgy is a way to form and fabricate alloys of metal. For this purpose, over the years, two methods have been devised. The first one is called sintering and the other one is known as metal injection molding. In the experiment conducted, two mixtures were used, A and B. their results have been discussed in detail in this report. This part of the report deals with a generic form of powder metallurgy. It focuses upon the forming of metal alloy in which boron has been added into with some quantity. The advantages and other effects of boron added steel will be discussed in this part of the report. This part also like in the experiment will tell about the effects of high temperature on the mixture when it is applied to the process when it is being made. Some key research papers will be read and reflected in this important part of the report to understand the phenomenon of boron added steel under high temperature process (German, 1990) EFFECTS OF BORON ADDITION IN STEEL Boron is a good element when it gets added in steel because it provides more hardness to the steel, as shown in the experiment conducted in class and the analysis that has been explain in the earlier part of this report. When boron is added to any type of low grade steel, it gets more hard than usual. The products of such mixture, the steel, are more hard and high quality in nature. These steels are used as construction material due to their hard nature and also forming cold steels such as in screws (Adam, 2000). The change of property will be discussed in this paper, which happens with the change of temperature applied and the quantity of boron added Boron is also known for another quality. It activates liquid phase sintering and lowering the sintering temperature that is required to make a very high dense metal (Raymond, 1994). The liquid phase comes from the presence of low melting-point eutectic reaction that happens when boron reacts with the metal with which it is being processed. Both forms a reaction at 1174o C when reacting with pure iron but at times forms a better boride phase when chromium is also present (Adam, 2000). Effect on the Mechanical Properties and Harden-ability of Sintered P/M by addition of Small amounts of Boron Minute quantity of boron, about 0.1 to 0.15 %, can bring enough hardness and strength in the upgraded steel. It lowers the level of the alloying element and increases the compact property of the powder. These minute quantities may be good enough to bring a lot of hardness in the steel, keeping in check that the right amount of temperature is applied. The terms that are constantly being used are sintering and hardenability. Sintering is known as the amount of which the martensite is formed when a required cooling rate is provided to the steel. Hardenability of steel, or any metal, is considered to be the diameter (maximum) of a cylinder that has a microstructure that is in the half of its centre after it has been quenched from the austinizing temperature (Reed, pp. 35) Temperature Effects on the Mixture For finding the correct answers related to the effect of temperature on the process of making PM steel with boron added, we need to study a lot of previous research done on this particular topic. The results will be described with the help of graphics and along with the description of the graph. Some of the results will be from previously conducted experiments and not this one. The general feeling about the PM alloy of boron is that it has higher quality finish and a superior sintering value. The proof of this statement will be provided by the effects of the addition of boron in low level steels, also increasing temperature to prove yet another fact described before. INVESTIGATION As said before, graph and references will be utilized to explain the phenomenon that is under consideration in this report. The figure shown is a very easy to understand the factors and effects that are being discussed. Furthermore, detailed description of the figure is proved for better understanding. The graph above, shows on the x-axis, the amount of boron added and the sintered density on the y-axis. There are three different temperatures that have been applied to the mixture. Different results are shown on the graph. It can be seen very distinctively that the addition of boron from a level of being zero to a 15 % quantity makes the sintered density increases, which means that the hardenability has also increased gradually with the increase in boron quantity, as the sintered density has been raised. At 0% addition of boron in the allow, the sintered density is about 7.14 g/cm3, which can be seen in the diagram. The graph shows very clearly, that the sintered density increases till the boron reaches 0.15 W/oB to 7.2 g/cm3. Another feature of this study and analysis includes the effect of temperature on such a mixture, which is of PM steel. There are three temperatures used, as shown in the graph (of a previous research, with ideal conditions). The three temperatures are 1120, 1175 and 1230 degree Celsius, which can be differentiated by the color coding described in the legend on the graph. Extreme temperatures are essential for forming high quality and sintered alloys. The increase of temperature applied in an alloy with boron already added will certainly increase the sintered density of the alloy. This has been proved by the analysis of the experiment conducted in the class and also will be described by the extracted graph and research. As it can been seen on the graph that even without the addition of boron, increasing the temperature will in turn increase the sintered density of the alloy that is being formed. In the shown graph, there is only one exception at the time of 0.05 boron addition that the temperature does not increase the sintered density. Other than that one instance, it can be seen that the increase in temperature with or without boron addition, will increase the sintered density and hardness quite handsomely CONCLUSION AND RECOMMENDATIONS The report, theoretically and practically both proves some findings. One that the temperature has a good effect on the alloy properties but especially when boron is added to the mixture that will make the alloy. Many scientists have proved the fact and it also registered in our experiment. There are some recommendations that should be made here. The first one is the use of the right temperature when sintering an alloy. More temperature can rough the surface and less can lower its positive properties. The second and most important recommendation is using boron in steel alloys to improve their strength. This feat can also be performed by adding chromium or nickel but both of those elements are very expensive. Boron is cheaper than both of them and brings almost the same results. Even if the results are not the same, it gives a lot of strength and good properties to the alloy. BIBLIOGRAPHY Fuhrer, Adam J. (2000) Hardenability of Sintered Fe-Ni-C-B Alloys, Senior Design Final Report, Drexel University, Philadelphia, PA. German, Raymond M. (1994) Power Metallurgy Science, Metal Powder Industry Federation, Princeton, NJ Hill, Reed E. (1994) Physical Metallurgy Principles. Boston. PWS Publishing Company James, Walter B. Ferrous Powder Metallurgy, Hoeganaes Corporation Training Manual. Randall, German M. (1990) Super solidus Liquid Phase Sintering Part I: Process Review, International Journal of Powder Metallurgy . Read More