YY/T 0988.2-2016Coatings of surgical implants - Part 2: Titanium and titanium-6 aluminum-4 vanadium alloy powders (English PDF)

Foreword

YY/T 0988 Coatings of Surgical Implants consists of the following parts:

--- Part 1: Cobalt-28 Chromium-6 Molybdenum Powder;

--- Part 2: Titanium and Titanium-6 Aluminum-4 Vanadium Alloy Powders;

--- Part 3 ~ Part 10 (Reserved);

--- Part 11: Tension Testing Method of Calcium Phosphate Coating and Metallic Coatings;

--- Part 12: Shear Testing Method of Calcium Phosphate Coating and Metallic Coatings;

--- Part 13: Test Method for Shear and Bending Fatigue Testing of Calcium Phosphate and Metallic and Calcium Phosphate/Metallic Coating;

--- Part 14: Stereological Evaluation Method of Porous Coatings;

--- Part 15: Test Method for Abrasion Resistance Testing of Metallic Thermal Spray Coatings. This Part is Part 2 of YY/T 0988.

This Part was drafted as per the rules specified in GB/T 1.1-2009.

This Part uses redrafting method to be drafted by reference of ASTM F 1580-2007 Standard Specification for Titanium and Titanium-6 Aluminum-4 Vanadium Alloy Powders for Coatings of Surgical Implants.

Technical differences between this Part and ASTM F 1580-2007 are as follows:

--- Regarding the normative references, this Part has made adjustments with technical differences; and delete 2.2 and 2.3 to adapt to the technical conditions of China.

--- Delete Clauses 8, 9, 10, and 11 of ASTM F 1580-2007.

Please note some contents of this Document may involve patents. The issuing agency of this Document shall not assume the responsibility to identify these patents.

1 Scope

This Part of YY/T 0988 specifies the requirements for pure titanium powder and titanium-6 aluminum-4 vanadium alloy powder used to form coatings on titanium alloy implants.

The powders specified in this Part can be coated by sintering process or thermal spraying process.

This Part specifies the requirements for powders and does not apply to the properties of coatings made of powders.

NOTE: Fine titanium powder may cause spontaneous combustion and shall be treated in accordance with relevant guidelines.

2 Normative References

The following documents are essential to the application of this Document. For the dated documents, only the versions with the dates indicated are applicable to this Document; for the undated documents, only the latest version (including all the amendments) is applicable to this Document.

ASTM B 214 Test method for sieve analysis of metal powders ASTM B 215 Practices for sampling metal powders ASTM B 299 Specification for titanium sponge ASTM E 11 Specification for wire cloth and sieve for testing purposes ASTM E 2371 Test method for analysis of titanium and titanium alloys by atomic emission plasma spectrometry ASTM F 67 Specification for unalloyed titanium, for surgical implant applications ASTM F 1472 Specification for wrought titanium-6 aluminum-4 vanadium alloy for surgical implant applications

AMS 2249 Chemical check analysis limits, titanium and titanium alloys

AMS 4998 Powder, 6-Al-4V

3 Significance and Application

Coatings made of metal powders are widely used to improve the adhesion between tissue and non-bone-cemented joint prosthesis. Such coatings also improve the adhesion of the acrylic bone cement to the prosthesis. This Part specifies specific requirements for metal powders used for coatings. See Appendixes A and B for principles and biocompatibility.

4 Manufacturing Method

The powder can be obtained by plasma rotating electrode method, inert gas atomization method, hydrogenation-dehydrogenation method or other methods that can produce powders meeting the requirements of this Part.

5 Chemical Requirements

5.1 The chemical composition of the powder shall meet the requirements in Table 1.

Table 1 lists the content requirements of major elements and minor elements for pure titanium powder and titanium-6 aluminum-4 vanadium alloy powder; and also lists the requirements of all important residual elements. Elemental compositions not listed in Table 1 do not require verification of compliance with this Part.

Appendix A (Informative)

Basic Principles Coatings made of metal powders are widely used to improve tissue adhesion to implants. Such coatings also improve the adhesion of the acrylic bone cement to the prosthesis.

The biocompatibility of metallic implants is directly determined by their composition. The titanium and titanium alloy powder components in this Part have been used in forged surgical implants and have been widely used in the preparation of porous coatings for commercial use.

The composition of oxygen, iron, carbon and nitrogen in pure titanium is specified in the standard ASTM F 67, Grade 4. The composition of silicon, chlorine, hydrogen and sodium elements is specified in the standard ASTM B 299, Grade-SL.

The composition of aluminum, vanadium, oxygen, iron, carbon, hydrogen and nitrogen in the titanium-6 aluminum-4 vanadium alloy is specified in the standard ASTM F 1472. The composition of copper and tin is specified in the standard AMS 4998.

See standard AMS 2249 for the maximum allowable deviation of product compositions. There are no accepted deviations for chlorine and sodium in titanium alloys.

Processing aids are often used to aid in powder processing and bonding of the porous coating to the implant surface. Determining suitable processing aids or explaining their use is beyond the scope of this Part. It is the implant manufacturer's responsibility to ensure that any processing aids or their residues do not impair the biocompatibility and other properties of the coating.

It shall be recognized that the heat treatment process used to produce porous coatings results in a microstructure that differs substantially from that of wrought titanium alloys. At the same time, the porous-coated implant has a larger surface area than a single implant. For these reasons, the evaluation of biocompatibility and corrosion resistance of coatings shall be performed on the final coating.

Likewise, the microstructural changes induced by these heat treatments lead to large differences between the corrosion fatigue properties and typical wrought titanium alloys. Therefore, the corrosion fatigue performance of the coating shall be evaluated.

Pore size and morphology are important factors affecting tissue growth and penetration of acrylic bone cement. The size, distribution and shape of the particles are critical to controlling the pore size and morphology of the final coating. The size and distribution of the particles is usually controlled by a mesh screen. For a given coating preparation process, the ASTM