MICROSTRUCTURE CHARACTERIZATION OF( Ni-PAL2O3) ELECTROLESS COATING OF LOW ALLOY STEEL (AISI 4140)

Abstract

In This paper investing micro hardness, surface roughness measurements of electro less composite of coatings (Ni-P-AL2O3). deposited in electro less immersion on low alloy steel. All Specimens (20 mm diameter × 10 mm height) were used as the substrates for low alloy steel (AISI 4041). were grinded and polished as ASTM by emery paper (tungsten oxide paper) no (400–2500). then samples were washed by distilled water and ethanol and dried by using an electrical dryer. Polishing was conducted by diamond paste, specimens were immersed in acetone for (60 min). Before coating, specimens were immersed in solution including materials (30 g/L NaOH, 60 g/L NaCO3 and 60 g/L NaPbo4) for two-minute period at( 75°C) temperature moving the electrolyte using magnetic stirring by supply power (3 volts) to remove oil and any dust from metal surface. After that, the specimens were washed with distilled water, and Placed in sulfuric acid solution (20%) for (10 sec).after that it directed immersion in coating solution. The electro less (Ni-P-AL2O3) coatings were prepared by using nickel chloride as a source of nickel in alkaline baths, using (alpha alumina).The formulas were characterized by means of measurements of micro hardness, surface roughness. Our the results revealed that the heat-treated sample (Ni-P-AL2O3) showed higher hardness (2061HV). Increasing in the concentration was noted of (AL2O3) induced as-coated(Ni-P) conversion structure from amorphous to crystalline. The composite coating (Ni-P-AL2O3) is better compared to the Ni-P coating, and they get even better with heat treatment increased. The addition of (AL2O3) makes the coating denser and the grain size to decrease according to the formulae being heat treated.