AN INVESTIGATION OF THE EFFECT OF HEAT TREATMENT ON SURFACE ROUGHNESS IN MACHINING BY USING STATISTICAL ANALYSIS

In the present paper, the effect of heat treatment on the surface roughness of AISI 4140 steel has been investigated by use of paired t-test and one way analysis of variance (ANOVA). The paired t-test was performed to determine the differences between the means before and after heat treatment. One way ANOVA was used to further evaluate the effect of heat treatment on the difference in variances between two groups. According to the statistical analysis, it was concluded that heat treatment has decreased the surface roughness at the 95% confidence level. The improvement of surface roughness varies from 37% to 45% with various combinations of experimental parameters.