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Functionally graded materials for erosion and wear resistance in downhole applications

IP.com Disclosure Number: IPCOM000103585D
Publication Date: 2005-Mar-18
Document File: 3 page(s) / 56K

Publishing Venue

The IP.com Prior Art Database

Abstract

Various types of coatings are applied to mechanical parts to handle hostile operating conditions downhole such as corrosion, erosion and wear resulting from numerous operations performed on a well. For example, excessive erosion is observed during hydraulic fracturing and gravel packing. Matrix acidizing imposes severe corrosion inhibition requirements. Hence coatings of various types are employed to achieve different functions; these include metallic allows, ceramics, plastics, and others. There are many ways to apply these coatings to mechanical parts such as physical or chemical deposition, thermal or plasma spray etc.

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Title of the invention: Functionally graded materials for erosion and wear resistance in downhole applications

Introduction

Various types of coatings are applied to mechanical parts to handle hostile operating conditions downhole such as corrosion, erosion and wear resulting from numerous operations performed on a well. For example, excessive erosion is observed during hydraulic fracturing and gravel packing. Matrix acidizing imposes severe corrosion inhibition requirements. Hence coatings of various types are employed to achieve different functions; these include metallic allows, ceramics, plastics, and others. There are many ways to apply these coatings to mechanical parts such as physical or chemical deposition, thermal or plasma spray etc.

Prior Art

The material coatings are generally thin (on the order of a few thousandths of an inch to about 118th of an inch) due to several reasons: (1) due to limitations of the coating application process, and (2) sometimes due to cost, Gold plating, for example, is generally cost controlled. Sometimes the material surface of a part is modified through a metallurgical process such as carburizing or nitriding. Again, these latter processes lead to fairly thin layers of materials of different properties than the substrate. The relatively small thickness of the modifying layers make them prone to mechanical damage due to scratching or presence of pin holes tend to compromise their corrosion protection capability.

Mechanical bonding of the coatings to the substrate is another factor that influences their performance. Typically the bonding strength is not very high due to various factors such as thermal stresses resulting from the different expansion rates of the coating and the substrate materials. The bond strength is also influenced by the chemical compatibility of the two materials.

A third factor influencing the performance of the coatings is the mechanical stress distribution in a part. Generally at the interface of the coating, higher stresses may be expected due to the abrupt changes in the mechanical properties (such as thermal expansion coefficients) of the two materials. For example if a part with tungsten carbide coating on a mild steel substrate is subjected to bending, we can expect a stress raiser effect at the coating interface (See Fig.l).

The present invention overcomes the above mentioned deficiencies of the coatings by providing a different method by creating a graded material through a laser-cladding process to achieve a desired functionality.

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Invention Description

The principle of laser cladding is to form a coating by melting the coating ma...