DE2606439C3 - Running surface coating for reciprocating pistons of internal combustion engines - Google Patents

Description

The invention relates to a running surface cover for reciprocating pistons of internal combustion engines according to the Preamble of claim 1.

A tread cover serving as overload protection is already known from DE-OS 2154953. There the shaft part of the piston is surrounded by a sleeve, the connection between the sleeve and The piston skirt is such that if there is a risk of piston seizure, e.g. B. due to increased operating temperature, the sleeve can detach from the shaft. This is intended to prevent the piston from seizing up in the cylinder the associated consequential damage to the entire engine can be avoided. Are interesting such precautionary measures, for example, with ship engines. There is the avoidance of consequential damage In the case of piston seizures, it is particularly important to avoid the damage that occurs, if necessary, solely from Have on-board personnel remedied or be able to keep them within limits until the next port is called.

When serving as overload protection covers, an essential requirement is that they in Normal operation of the engine as highly wear-resistant as possible and, if possible, if the piston is threatened with seizing are compliant.

Tread coatings or coatings per se are of course already in the most varied Known variations. So shows z. B. GB-PS 448766 a so-called anti-friction coating made of an alloy containing, in particular, copper and lead. For the same purpose are in GB-PS 573 431 Tin alloys, zinc or cadmium or zinc-cadmium alloys as well as lead and bronze suggested. In DE-PS 594387 a metallic coating is also used for the running surface of a piston proposed that made of a friction-reducing and crushable metal such. B. Tin is supposed to exist. The aim there is aimed at To be able to install the piston in the cylinder with almost no play. From DE-Gbm 1914396 there is also one Coating of a sprayed-on mixture of white metal and molybdenum or tungsten disulfide is known.

However, all these coatings have the disadvantage that they are not wear-resistant in normal operating conditions to be enough.

To remedy this is the task of the present Invention.

It is achieved by a coating according to the characterizing part of claim 1.

Particularly advantageous alloy compositions are specified in the subclaims.

An embodiment of the invention is described below.

The pseudo-alloy representing the piston running surface coating is made according to that known per se Metal arc spray applied to the base material of the piston. Sprayed in an arc two wires, one made of Al Si 12 and the other made of 86 wt% Sn, 8 wt% Sb and 6% by weight Cu. They thus form the starting material for the pseudo-alloy coating. The pseudo-alloy produced itself has the following composition:

4.5 wt% Si

1.7 wt% Cu
32.0 wt% Sn

3.8 wt% Sb
Remainder Al

The particular advantage of the generated pseudo-alloy is that the wire materials fed in When molten, do not mix completely, only partially. This creates an imagination heterogeneous layer structure, in which structural components from the starting materials and mixtures (intermetallic compounds) are present from these. In the case of the coating according to the invention this has the advantage that, in the event of thermal overload, the softer alloy components first yield, while the firmer ones give the coating a certain strength as a kind of grid. For example, the specified coating exhibits compressive strength behavior at temperatures from 20 to 80 ° C which is around 50% higher than with conventional Sn or Pb alloys. Likewise, the adhesive wear resistance is increased by about 70% and the hot hardness by about 100%. improved in a temperature range between 20 to 150 ° C. As with overloads in the critical

3 4

Temperature range contained in the coating. The layer thickness is chosen so that

Sn structure areas can be melted or melted for certain predetermined overload temperatures

As with conventional Sn alloys, the piston with its base material is almost

Layer can be defined and with increasing load the coating is still completely pushed off

also pushable. *> does not eat in the cylinder.

Claims (1)

Patent claims: 1. running surface coating for reciprocating pistons of internal combustion engines, especially large> internal combustion engines, which act as a kind of overload protection acts and is highly wear-resistant in the normal operating state of the engine and in thermal Overstressing is deformable, characterized in that it consists of a '«' So-called pseudo-alloy of the composition which is thermally sprayed on in a manner known per se 2.5 to 5.5 wt% Si
1 to 2.5 wt% Cu i ^r > 25 to 40 wt% Sn
2.5 to 4.5 wt% Sb
Remainder Al consists, whose starting materials are two alloys of the compositions Al Si on the one hand μ and Sn Sb Cu on the other hand. 2. tread cover according to claim 1, characterized by a composition of Pseudo alloy with 4 to 5 wt% Si - >> 1.5 to 2 wt% Cu
30 to 35 wt% Sn
3.5 to 4 wt% Sb
Remainder Al 2. Tread coating according to claim 2 with i »alloys of the starting materials of the composition of 5 to 12 wt .-% Si, remainder Al for one and 80 to 90 wt .-% Sn, 6 to 10 wt .- % Sb, 4 to 8 wt% Cu for the other. 4. Tread coating according to claim 3 with π alloys of the starting materials of the composition of about Al Si 12 for one and about 86 wt% Sn, 8 wt% Sb, 6 wt% Cu for the other. 5. tread coating before and after a four-w previous claims, characterized in that the pseudo-alloy is composed of the same amounts of the starting materials.