Efficiency of using MODENGY solid-film coatings for hydraulic cylinders

INTRODUCTION

Hydraulic cylinders are an important heavy-loaded part of the machine tools, hydraulic pressed, specialty equipment as well as a great deal of special machinery (such as excavators, loaders, tractors, lifting devices and mechanisms).

Manufacturers of hydraulic drives actively use MODENGY anti-friction solid-film coatings of the Russian development. These materials are applied onto the internal surfaces of the hydraulic cylinders liners (see Fig.1), onto the threaded connections of double hydraulic cylinders (see Fig.4), rod bushings, D-valves of hydraulic distributors and hydraulic pumps.

Figure 1 – Hydraulic cylinder before and after applying MODENGY 1066 coating

Despite its small thickness (20 ± 5 µm), a separating layer of the coatings has resistance to hydraulic oils, prevents stick-slip motion, reduces losses for friction as much as possible, and significantly extends service lifetime of the equipment.

ISSUES AT OPERATING HYDRAULIC CYLINDERS

Manufacturers and the organization operating hydraulic drives face the issue of corrosion appearing on the internal surface of the hydraulic cylinders liners. This relates to condensate forming in the hydraulic fluid.

At running under conditions of subzero temperatures, oil viscosity increases what causes forming dry friction zone in the contact zone of the liner internal surface and the cup, and this affects adversely operability of the unit.

Wear of the liner reveals in the form of scores and scratches on its surface, and as a result hydraulic fluid ‘restart’ (flow) from one chamber to the other forms, what causes improper functioning of the hydraulic cylinder. The particles of the worn liner surface not always can be caught by the filters, and can get into the hydraulic distributor what causes system failure, and necessity of expensive repairs.

EFFICIENT SOLUTION IS MODENGY 1066 COATING

To improve reliability, and extend service lifetime of the hydraulic cylinders, MODENGY 1066 product (see Fig.2) based on molybdenum disulfide and graphite from the Russian Modengy comany is used.

MODENGY 1066 solve the following tasks:

• Corrosion protection for the liner internal surface
• Preventing scuffing forming
• Providing smooth going

This coating has high adhesion and strongly holds on the surface of the treated parts, keeps its operability under conditions of negative temperatures (down to -70 °С).

Figure 2 - MODENGY 1066 coating

MODENGY 1066 is a coating with high load-carrying capacity, and significant anti-corrosive properties (more than 300 hours, according to the results of the accelerated tests in neutral salt mist chamber on ISO 9227 standard). The basic performances of MODENGY 1066 are given in Table 1.

Table 1

1. Prior preparation, cleaning, and activation of the part surface
2. Applying solid-film coating by the spraying-out method
3. Coating curing by the method of heating the part in a kiln

TESTS RESULTS

The tests of the hydraulic cylinder with MODENGY 1066 coating on its liner internal surface have been held at the site of the industrial equipment manufacturer. They were performed on a special stand for up to 10,000 cycles what meets the full functioning term of the equipment.

After the tests has been completed disassembly of the drive was done. At visual examination, no scores on the liner internal surface were observed. The coating had neither peeled off, nor destroyed.

Measuring the coating thickness after the drive had completely worked-out its lifecycle showed minimal abrasion: 2 to 3 µm. Based on the tests results, the manufacturer has recommended use of MODENGY 1066 coating on the hydraulic cylinders liners internal surfaces (see Fig. 3).

Figure 3 - MODENGY 1066 coating on the hydraulic cylinder liner

Use of MODELING 1005 anti-friction solid-film coating in the threaded connections of double (tandem) hydraulic cylinders has also demonstrated successful result.

Double hydraulic cylinders elements are subjected to very high loads (tensile load reaches 35 tonnes). To prevent thread galling and sticking under such conditions, MODENGY 1005 wear-resistant coating based on molybdenum disulfide is applied onto external and internal threaded parts of the parts (see Fig.4).

Figure 4 – Threaded connections of the double hydraulic cylinders treated with MODENGY 1005 coating

This coating is not squeezed out of the contact zone even at high contact pressures providing lubricating-and-separating layer between the conjugated elements.

CONCLUSION

MODENGY anti-friction solid-film coatings have low friction coefficient, high load-carrying capacity, high anti-corrosive and anti-scuffing properties.

This enables to use these products successfully in such heavy-loaded units like hydraulic cylinders.