|Content Type||Conference Paper|
|Title||Proposed Standard Carburization Test Method|
|Authors||George Y. Lai, Corrosion & Metallurgical Consulting; Brian Gleeson and Bingtao Li, Iowa State University; H. Lee Craig, Materials Technology Institute of the Chemical Process Industries|
|Source||CORROSION 2003, March, 2003 , San Diego Ca|
|Copyright||2003. NACE International|
|Keywords||carburization, standard test method, test procedures, performance ranking, Fe-base alloys, Ni-base alloys|
A standard carburization test method has been developed that will allow investigators to generate carburization data under the same test parameters and procedures. By using such a standardized test, users can cross-check and compare data from different sources when selecting a candidate alloy or alloys. The test method is simple, and can be performed reliably and consistently by laboratories without such equipment as gas chromatograph, dew point hygrometer or oxygen probe. The test is conducted at 982° C (1800° F) for 96 hours in H2 containing 2% CH4. A given test involves a total of twelve (12) specimens, i.e., four (4) rows of three, with the test specimens cycling to room temperature every 24 hours in order to rotate positions. With strict recommended procedures, along with specimen rotation and a control specimen at each row, the tests can be performed reliably and consistently in a normal tube furnace. Methods of sample evaluation are also recommended for assessing the degree of carburization. Test results are discussed with particular reference to test parameters and procedures, as well as the methods of sample evaluation.
Carburization is an important high-temperature corrosion phenomenon that significantly affects materials performance in a number of industrial processes1,2. Selection of proper alloys for process equipment is critical in minimizing the equipment failures, thus unscheduled shutdowns, and maximizing operation efficiency. An informed alloy selection requires an adequate and reliable database from a large group of candidate alloys. A review of the literature shows that it is almost impossible to compare various sets of data generated from different laboratories. This is primarily due to the fact that no standard test method was available and, hence, the testing and assessment of results were highly varied. Furthermore, previous investigations used different test parameters and conditions for data generation. Test environments, temperatures and exposure times, for examples, were different from different investigators. Matters are further complicated by the fact that the data were reported in different ways. Some reported bulk carbon content, while others reported weight gain per unit surface area of the test specimen. Still others reported the depth of carburization. Basically, there has not been a standard test method that investigators from different laboratories and different alloy producers can follow when generating carburization data.
A program* was set up to address this long-recognized need for developing a common test method and to perform a state-of-the-art review on carburization and develop best practices for testing alloys in carburizing environments. As a result of this program, a report entitled Carburization ? A High Temperature Corrosion Phenomenon, which documents the state-of-the-art review and best practices for testing alloys, was prepared by Grabke2. The program* also included the development of an ASTM Specification on a standard test method for gas carburization. This part of the program was championed by George Lai and managed by Lee Craig. During the course of developing this standard test method for gas carburization, experimental tests were carried out by Bingtao Li and Brian Gleeson. The tests were intended to verify the test parameters and procedures.
The present paper discusses the proposed test method for gas carburization with emphasis on the test results related to test parameters, procedures and evaluation methods.
PRIMARY TEST PARAMETERS
Major test parameters were discussed in detail by Grabke2. A test environment consisting of H2 and 2 % (vol.%) CH4 was recommended. This test environmen
|File Size||233 KB||13|