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Discussion of Results:

There were a series of labs performed to find out the changes in properties of the metals

and different kinds of steels having different properties, after passing through different

treatments that were supposed to induce changes in their physical properties while the major

focus was developed on the hardness and tensile strength of these metals. In the first lab we

studies about the hardness of different samples of the steel that included 1018, 1090, 1045 and

4041 steel samples. All these specimen were tested for their harness factor which measured on

the HRC harness scale after experimenting with the harness tester. Three test were performed for

the three samples and recorded values showed that 1018 had values 28, 30, 29 and 29 for the

test1, test2, test3 and average respectively. Similarly 1045 had these values as 15, 15, 14 and

14.6 respectively and for the 4140 these values were 26, 29, 29 and 28 respectively. The results

showed that 1018 was the most hardest among these samples.

The next lab was then performed to find out the effect of different heat treatments on the

hardness factor of these tested samples. Two of the samples were fully annealed and two of them

were quenched. The only different in these two heating processes was among their method of

cooling the samples once they were heated to the required temperature to reach the Austenite

range in equilibrium diagram. The quenched samples were directly cooled by putting the baked

samples into the water at room temperature whereas the annealed samples were allowed to cool

slowly over the period of a night. The samples 1045 and 1090 that were quench hardened.

Results showed that their hardness values reached 40, 42 42 and 41.33 for the test1, test2, test3

and average respectively for the 1045. Similarly the values went at 64, 65, 66 and 65 for the

sample 1090. All the hardness values were measured on the HRC scale. The values of the

approximate tensile strength were 188 Ksi and 385.38 Ksi for the 1054 and 1090 respectively.

The values of the annealed samples for the three test and their average was 59, 66, 58 and 61 for

the sample 1018 while its tensile strength ranged was found to be 346 Ksi. The harness of the

annealed samples was measured on the HRB scale. The tensile strength of the sample 4140 was

found to be 64 Ksi.

The next lab was then performed to create the mounts of the Bakelite for the polishing of

these samples. This is done by treating the Bakelite powder at a very high temperature and

pressure that melts it and converts it into a thermosetting plastic that once formed cannot be

recreated. Then all the samples were grinded and polished to find out their microscopic

structures. The steps included in the grinding were rubbing the samples with silicon carbide

papers of grit size 180, 320 and 600 with the wheel speed and pressure of 300 rpm and 45 Ksi

respectively. Then the polishing was performed with the help of the red felt cloth and Al2O3 and

water. The surfaces achieved after the polish were very reflective.

6% nitric acid solution will be used for the etching of the sample’s surfaces to makes

them readable under the microscope. The nitric acid is a very strong chemical agent used for

etching because of its corrosive properties. The images gathered after the etching showed that the

sample 1018 and 4140 that were annealed had now a grain structure similar to pearlite and

cementite having a mix of different layers of these two compounds. The sample 1045 and 1090

that were quenched had transformed their structure into Martensite and had undergone changes

in their structural properties from BCC to FCC and FCC to BCT.

These labs were a great learning experience as all that was studied in the text and covered

in the lectures was seen actually happening after performing the experiments.