GMW17928

Description / Abstract: Introduction

Note: Nothing in this standard supercedes applicable laws and regulations.

Note: In the event of conflict between the English and domestic language, the English language shall take precedence.

Purpose. This is a material test procedure to evaluate wear of materials during oscillating sliding using a pin-on-plate apparatus. Effects taken into consideration are loading, frequency, stroke, temperature and environment. Materials are tested in pairs under nominally non-abrasive, unlubricated conditions. The principal areas of experimental attention in using this type of apparatus to measure wear are described. The coefficient of friction, wear volume and wear depth may also be determined.

Applicability. This test procedure was developed to help evaluate wear on turbo charger waste gate linkage components but could potentially be applied to other components if test conditions are modified to reflect the particular conditions of that component. This test allows for relative comparisons between different linkage systems including materials and material conditions to evaluate wear mechanisms and their rate of progression, including the effects of temperature, corrosive environments and generated third body particles. This validation procedure is not intended to replace engine or vehicle durability testing. Instead, it is intended to evaluate the linkage subsystem in a controlled and repeatable environment in advance of engine and vehicle availability. Therefore, the objective is to bench test candidate linkage materials in a fixture in a laboratory environment.

Remarks. This specification is based off of ASTM G99, which was modified specifically for the turbo charger. There are various wear mechanisms. Some of the more common ways that wear can occur in the linkage interfaces are listed in Table 1. This accelerated test procedure is intended to expose the candidate linkage materials to these types of wear mechanisms to the extent that the linkage is expected to be exposed to them in the vehicle application. A rigorous process of cyclic loading under typical and high temperature conditions combined with corrosive environment exposure is utilized to provide an accelerated test approach.

Summary of Test Procedure. Two specimens are required; one, a pin with a radiused tip, is position perpendicular to the other, a flat plate. The test machine causes the pin specimen to slide in an oscillating fashion across the plate. The pin specimen is pressed against the plate at a specified load by an arm or lever via spring, hydraulic or pneumatic means. A heating method is applied.

Measuring Wear. Wear results are reported as both wear depth in millimeters and volume loss in cubic millimeters for the pin and plate separately. The amount of wear is determined by measuring appropriate linear dimensions of both specimens before and after test. This can be determined by any suitable metrological technique, such as electronic distance gaging or stylus profiling. Mass loss is often too small to measure precisely. Note that wear volume plots may display non-linear relationships between wear volume and distance over certain portions of the total sliding distance and linear relationships over other portions. Causes for such differing relationships include initial break in processes, transitions between regions of different dominant wear mechanisms, wearing through heat treated areas, and so forth. The extent of such non-linear periods depends on the details of the test system, materials, and test conditions. It is not recommended that continuous wear depth data obtained from position-sensing gages be used because of the complicated effects of wear debris and transfer films present in the contact gap, and interferences from thermal expansion or contraction.