Control of microhardness of nickel-phosphorus coatings in amorphous and crystal states, taking into account requirements to quality of supplied products

The microhardness of a nickel-phosphorus coating 60 μm thick chemically applied to a steel substrate from an alkaline solution was determined at loads from 0,1 to 0,5 kgf. The control was carried out on preliminarily prepared samples of steel 09G2S, which passed the stage of crystallization annealing of the coating to the required hardness. The quality of the coating after the control and after 24 hours was evaluated with a reagent consisting of potassium synergistic and sodium chloride. It is established that the load is 0,2; 0,3 and 0,5 kgf are not suitable for reliable measurement of the microhardness of the coating due to a violation of its integrity and distortion of the microhardness indicators. A load of 0,05 kgf is unacceptable due to obtaining diagonals that are a multiple of the smaller confidence interval of 0,02 mm. The conducted studies and the revealed patterns made it possible to select the optimal load (0.1 kgf) used in determining the microhardness of a 60 μm thick coating, which guarantees the preservation of the quality of parts used in the oil and gas industry in the hardness range of 1000 HV and more.