Postcarburizing Mechanical Treatments

Carburizing ◽  
1999 ◽  
pp. 199-225
Keyword(s):  
High Temperature ◽  
Stress State ◽  
Fatigue Resistance ◽  
Internal Oxidation ◽  
Shot Peening ◽  
Transformation Products ◽  
Roller Burnishing ◽  
Temperature Transformation ◽  
And Behaviors

Abstract Mechanical treatments such as grinding and shot peening are often employed in the production of case-carburized parts. Grinding, besides restoring precision, removes carbide films, internal oxidation, and high-temperature transformation products. Shot peening strengthens component surfaces and induces a stress state that increases fatigue resistance. This chapter describes both processes as well as roller burnishing. It explains how these treatments are applied and how they influence the microstructure, properties, and behaviors of case-hardened components. It also addresses process challenges, particularly in regard to grinding.

Internal Oxidation

Carburizing ◽  
1999 ◽  
pp. 11-36
Keyword(s):  
Carbon Dioxide ◽  
Internal Oxidation ◽  
Material Design ◽  
Transformation Products ◽  
Fracture Behaviors ◽  
Gas Carburizing ◽  
Fatigue And Fracture ◽  
Temperature Transformation ◽  
And Performance ◽  
Composition Gradients

Abstract Gas carburizing is known to promote internal oxidation in steel which can adversely affect certain properties. This chapter discusses the root of the problem and its effect on component lifetime and performance. It explains that gas-carburizing atmospheres contain water vapor and carbon dioxide, providing oxygen that reacts with alloying elements, particularly manganese, chromium, and silicon. It examines the composition and distribution of oxides produced in different steels and assesses the resulting composition gradients. It describes how these changes influence the development of high-temperature transformation products as well as microstructure, hardenability, and carbon content and properties such as fatigue and fracture behaviors, hardness, and wear resistance. It also explains how to manage internal oxidation through material design, process control, and other measures.

Identification of non-martensitic transformation products(NMTP) in a carburized 8620 steel

1995 ◽  
Vol 53 ◽  
pp. 526-527
Author(s):  
William T. Donlon ◽  
William E. Dowling
Keyword(s):  
Mechanical Properties ◽  
Martensitic Transformation ◽  
Fatigue Resistance ◽  
Internal Oxidation ◽  
Oxygen Potential ◽  
Transformation Products ◽  
Alloy Steels ◽  
Machining Operations ◽  
Alloy Depletion

Additions of Cr and Mn to steel are intended to increase hardenability (the ability to form martensite on cooling from austenite) and thereby improve the mechanical properties. However, conventional gas carburization of alloy steels containing Cr and Mn as well as Si will produce oxides of these elements (internal oxidation) near the surface (due to the oxygen potential of the carburizing atmosphere). Additionally, the oxidation of these elements locally reduces the hardenability of the alloy, creating the potential to produce non-martensitic transformation products (NMTP) near the surface. These oxides and the associated NMTP have been shown to decrease the fatigue resistance of carburized steels if they are not removed by subsequent machining operations. The objective of this study is to characterize the oxides, identify the NMTP and assess the degree of local alloy depletion in a carburized 8620 steel (0.21 C, 0.93 Mn, 0.023 S, 0.12 Si, 0.49 Cr, 0.38 Ni and 0.17 Mo).

HAYNES ALLOY No. 625SQ

Alloy Digest ◽  
2003 ◽  
Vol 52 (8) ◽  
Keyword(s):  
Grain Size ◽  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Fatigue Resistance ◽  
Heat Treating ◽  
Temperature Performance ◽  
Haynes Alloy

Abstract Haynes 625SQ alloy is a modification of Haynes 625 alloy (see Alloy Digest Ni-354, January 1988) with tighter controls on chemistry and a finer grain size for fatigue resistance up to 680 deg C (1250 deg F). This datasheet provides information on composition, physical properties, microstructure, elasticity, and tensile properties as well as fatigue. It also includes information on high temperature performance as well as heat treating. Filing Code: Ni-612. Producer or source: Haynes International Inc.

Research on a Surface Shot Peeling Process for Increasing the Anti-Oxidation Property of Super304H Steel in High-Temperature Steam

2014 ◽  
Vol 908 ◽  
pp. 77-80 ◽  
Author(s):  
Yan Hui Li ◽  
Shu Zhong Wang ◽  
Pan Pan Sun ◽  
Xue Dong Li
Keyword(s):  
High Temperature ◽  
Shot Peening ◽  
Austenitic Steels ◽  
Detailed Surface ◽  
Before And After ◽  
Main Chemical Composition ◽  
Oxidation Properties ◽  
High Temperature Steam ◽  
Super304h Steel ◽  
Generation Unit

At present, the superheater and reheater pipes in supercritical and ultra-supercritical boilers have encountered with widespread problems of high temperature steam oxidation, seriously affecting the operation safety and economy of the power generation unit. After several tests and contrastive analysis on the main chemical composition and microstructure of specimens before and after shot peening treatment, this paper developed a set of detailed surface shot peening process with specific process parameters, and finds that for the Super304H oxide film, the relative content of Cr element increases by shot peening treatment, with the relative Cr content of the treated specimen being 2.65% higher than that of the untreated, displaying that the anti-oxidation properties of high chromium austenitic steels in high temperature steam is effectively increased.

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