1、 ENGINEERING MATERIAL SPECIFICATIONDate Action Revisions 2005 02 04 Revised Inserted 3.0; Deleted 3.1, 3.4, 4 1996 08 05 Revised Completely Revised and Updated W. Janssen, EAO 1995 05 10 Released EP00E10517874000 W. Janssen, EAO Printed copies are uncontrolled Copyright 2005, Ford Global Technologie
2、s, LLC Page 1 of 3 BORONIZING OF GEARS WSS-M99A5-A 1. SCOPE This specification outlines the approved process for producing a wear resistant surface based on a phase compound, which consists of Fe2B mainly. This process standard defines the method of boronizing and the subsequent hardening and temper
3、ing of ferrous parts. The boronizing process is a diffusion process by which one or more intermetallic phases are obtained by diffusing Boron into the surface of metallic materials. The Boron can be diffused into the surface of a material by means of a paste or powder. 2. APPLICATION This process is
4、 used on components, such as gears, for gasoline and diesel engines produced from unalloyed/low alloyed steel with the exception of Si-alloyed steel, where the wear resistance shall be solved mainly. 3. REQUIREMENTS 3.0 STANDARD REQUIREMENTS FOR PRODUCTION MATERIALS Material suppliers and part produ
5、cers must conform to the Companys Standard Requirements For Production Materials (WSS-M99P1111-A). 3.2 BORIDE LAYER 3.2.1 Structure of Layer The structure of the layer should consist of a single compound of Fe2B, continuous compounds of FeB are not permissible. 3.2.2 Thickness The thickness of the b
6、oride layer shall be 0.03 - 0.06, unless otherwise specified on the engineering drawing. The thickness of the boride layer shall be measured perpendicular to the surface where the boride zone contrasts with the matrix. The measurement of thickness shall be determined by metallographical method. The
7、value of the layer thickness is defined as the mean depth which is calculated from the average of the teeth penetration and the minimum distance of the matrix from the surface. (Etching with 2 - 3% nitric acid, recommended magnification 200x) ENGINEERING MATERIAL SPECIFICATIONWSS-M99A5-APrinted copi
8、es are uncontrolled Copyright 2005, Ford Global Technologies, LLC Page 2 of 3 3.3 HARDNESS (ISO 4545/ISO 6507) Unless otherwise specified, the hardness shall be checked in the cross section as following: According to ISO 6507 1500 - 2000 HV 0.025 According to ISO 4545 1500 - 2000 HV 0.025 5. GENERAL
9、 INFORMATION The information given below is provided for clarification and assistance in meeting the requirements of this specification. 5.1 RECOMMENDED PROCESS 5.1.1 Prior Microstructure Prior to boronizing, the parts have to be normalized in a controlled atmosphere. The normalizing temperature sho
10、uld be in agreement with the boronizing temperature. 5.1.2 Surface Condition Parts to be boronized must be completely dry, free of oil, grease, rust and scale and must not be plated with copper, zinc, or tin. 5.1.3 Furnace Atmosphere The boronizing process has to be carried out in a protective atmos
11、phere. As a protective atmosphere the inert gas like Argon, NH3-cracked gas or N2-gas has to be used. The using of an oxygen-containing compound such as CO-, CO2-gas, endo- or exogas or methanol-cracked gas is not allowed, caused by reaction with boron responsive ferricboride. 5.1.4 Temperature The
12、temperature shall be controlled within +/- 5 C of set point, as evidenced by continuous recording pyrometers. Also, the mean isothermal shall not differ by more than 15 C from one part of the load and another as measured by use of thermocouple within the load. 5.2 PROCESS: BORONIZING 5.2.1 Boronizin
13、g Medium The process is such that the boronizing shall be carried out with Boron-paste or Boron-powder being composed of Silicon- and Boroncarbids and suitable activators. The application of used powder is not allowed. 5.2.2 Loading of Charge The parts must be bedded in a boronizing powder or coated
14、 by boronizing paste in such a way that the area, which has to be boronized, is guaranteed. ENGINEERING MATERIAL SPECIFICATIONWSS-M99A5-APrinted copies are uncontrolled Copyright 2005, Ford Global Technologies, LLC Page 3 of 3 5.2.3 Heat Treat Cycles The required heat treatment process is carried ou
15、t in the following stages: Preheating: To minimize the building of the FeB-layer, the parts shall be past the critical temperature range between 700 C and 800 C with the greatest speed. It is recommended to preheat the charging devices at approximately 600 C. Boronizing: The preheated charge has to
16、be heated up to the boronizing temperature between 850 C and 1,000 C. The holding time depends on the drawing requirements. Cooling: The parts must be cooled down under controlled conditions to 200 C or less. 5.3 POST TREATMENT To improve the mechanical properties of the boronized component, a heat treatment such as hardening and tempering should be performed. The use of a salt bath containing cyanide is not allowed due to damage of the boride layer by dissolution.
