Research On The Wear Resistance Of Micro-structure Of Alloy-cast-iron Cylinders And Wear Mechanism Analysis

Alloy cast iron cylinders are still the mainstream products used in diesel engines today, the reason is their excellent wear resistance, low cost, high price performance ratio and good processing techniques. The hard phases in alloy cast irons are mainly phosphor eutectics, alloy carbide and alloy nitride according to different component of the cylinders. Wear testing method is the main method that researchers used to investigate wear mechanism. These methods can indicate the different wear resistance of different cast irons, when the actions of the phases in the materials of cylinders are mentioned, they are not the effective method. The micro structure of the cylinders is mainly pearlite or bainite, which is always called cylinder Matrix. Because hardness is higher, the hard phase is higher in the contacting surface than the matrix in the process of wear. So hard phases have to bear mostly of the contacting stress and the matrix is protected accordingly. That is the double-contacting-surfaces theory people used to explain the wear mechanism of the cast cylinders which contain the hard phases. It is obviously that the theory did not show us the dynamic process of the wear, and the action of the hard phases is not very clear due to their different size, locality and contacting mode. In this paper, FEM (Finite Element Method) and wear testing method are combined to investigate its mechanism further, the results are as follow:1 The dynamic processes of friction were gained between the asperity of the piston ring and the cylinder matrix which contain or not contain hard phase, including the dynamic transformation of stress, plastic strain and topography of the contacting surface. And the better the material characteristics is, the wear properties are better.2 The influences of the existence of the hard phases in martrix on the wear were: preventing the expand of the plastic areas of the matrix; detaching the plastic areas; thereby preventing the slippage of dislocation and the stream of the martrix. That was the reason of good wear property of the alloy cast cylinders. In another aspect, the existence of hard phases makes some area of the matrix stress concentrate. So the probability of adhere and destroy became large, that is the adverse side.3. Wear testing of three kinds of cylinders proved that: the wear properties of cylinder BNb and the cylinder Nb which include the hard phases are better than the cylinder F which owned not hard phases.