The convection coefficient is an important thermal property. In this study, using an infrared thermometer, the convection coefficient of still air is estimated. First, the sample is heated in a sintering oven, then placed on a wood table for obtaining an almost adiabatic boundary, finally its temperature is recorded with respect to time using an infrared thermometer. The data is curve-fitted to find the sample temperature as a function of time. Using the sample’s physical dimensions, the specific heat capacity and the mass of the sample, the convection coefficient of still air is estimated.

The aim of this study was to investigate the effect of low temperature aluminizing process on microstructure and dry sliding wear properties of Mirrax steel. Low temperature aluminizing process was applied on Mirrax steel at 600, 650 and 700°C for 2, 4, 6 hours. The packs for process were prepared using pure aluminum powder as aluminum deposition source. Ammonium chloride NH₄Cl and Seydisehir Al₂O₃ powder were used as activator and inert filler, respectively. SEM/EDS and XRD analysis were applied for characterization of the coating surfaces. Variation on layer was determined from the surface to the inner and varied between 1µ to 50 µm which was increased with higher process temperature and time. After deposition process coating layer hardness value increased to 1000 HVN whereas the hardness of the matrix was 250 HVN. The wear tests were performed using a ball-on disc tribometer under 5N load at room temperature and 500°C on aluminized and untreated mirrax steel. In both room temperature and high temperature wear tests, it was determined that aluminizing process increased the wear resistance of mirrax steel. Elongated aluminizing time and temperature were also increased wear resistance. Uncoated and thin-coated samples generally exhibited wear in the form of plastic deformation and adhesion related ruptures. A high degree of tribological layer was observed on the wear trace on samples with high coating thickness, especially in high temperature tests. Therefore, the volume losses in these samples were caused by fatigue crack formation and delamination.