TEST. Hardness Control of Coating on Steel Discs with Diameters of 50 and 65 mm

Customer. LLC "Hydrotechmash" (Belgorod Region, Stary Oskol) is one of Russia's leading enterprises in the production of hydraulic cylinders and industrial equipment.

Control Object. Samples of steel discs in the form of rods with different types of coatings, with diameters of 50 and 65 mm.

Task. Selection of optimal equipment for controlling the hardness of the coating on steel discs.

Hypothesis and Test Preparation. The customer did not specify the steel grade and type of coating for the samples. The 50 mm diameter sample has a matte coating, while the 65 mm diameter sample has a mirror-like coating. The surface in both cases is smooth (does not require cleaning).

Considering the specifics and dimensions of the rods, our laboratory staff decided to use a ultrasonic hardness tester TKM-459C with a type "A" standard probe. For convenience in taking measurements, the samples were clamped in large metal vises.

Results. Each object underwent 5 Rockwell C hardness measurements; the average value was calculated.

Sample Diameter, mm	Mass, kg	Measurement Results Series, HRC	Average Value, HRC
50	2.3	71.6 / 70.6 / 70.5 / 70.8 / 69.4	70.6 (Fig. 1)
65	4.18	55.0 / 54.9 / 55.6 / 56.1 / 55.8	55.5 (Fig. 2)

The customer was satisfied with the hardness measurement results of the steel disc coatings and purchased a ultrasonic hardness tester TKM-459C; a U-459 positioning attachment for comfortable work on the round surfaces of rods; and a set of Rockwell hardness reference samples.

Our Recommendations. For controlling similar products, it is necessary to:

• Clean the control area if the roughness is high;
• Use vises to secure the objects;
• Ensure the probe is positioned perpendicular to the measured surface (it is advisable to use the "U-459" positioning attachment);
• Maintain the recommended distance between indenter impressions - at least 1 mm.

Contact the specialists at NPP "Mashproekt" to select equipment for solving your specific tasks.