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Investigation of the in vitro corrosion behavior and biocompatibility of niobium (Nb)-reinforced hydroxyapatite (HA) coating on CoCr alloy for medical implants Balraj Singh1, Gurpreet Singh1,a)

, Buta Singh Sidhu2

1

Department of Mechanical Engineering, Punjabi University, Patiala, Punjab 147002, India Dean of Planning and Development, MRS Punjab Technical University, Bathinda, Punjab 151001, India a) Address all correspondence to this author. e-mail: [email protected] 2

Received: 28 December 2018; accepted: 27 February 2019

In this study, a niobium-reinforced hydroxyapatite (HA-Nb) coating was developed on cobalt–chromium (CoCr) alloy by plasma spraying with three varied levels, i.e., 10, 20, and 30% of weight percent (wt%) of Nb content. The corrosion behavior and biocompatibility of the samples were analyzed through electrochemical corrosion testing and cytotoxicity studies, respectively. The results of corrosion testing revealed that the HA coating increased the corrosion resistance of the CoCr alloy, and with the incremental increase of Nb reinforcement in HA, corrosion resistance was further enhanced. The HA-30Nb coating demonstrated the finest corrosion resistance with the highest Ecorr and lowest Icorr values, which were about one order of magnitude lower in comparison to the bare CoCr alloy. The surface hardness increased and the surface roughness decreased with the increase of Nb content in the coating. Wettability analysis revealed that HA and HA-Nb coatings had a hydrophilic nature. HA-Nb coatings demonstrated a significantly better cell proliferation than the CoCr alloy.

Introduction Titanium alloys, stainless steel (SS), and CoCr alloys are the commonly used metallic biomaterials in biomedical implantology [1]. Among these biomaterials, CoCr alloys are widely used as orthopedic implants, particularly in dentistry and total joint replacements (TJR) because of their robust mechanical properties and wear resistance [2, 3]. However, the ions (Co21, Cr31, and Cr61) that release because of the excessive corrosion of CoCr alloys induce allergic reactions and can even cause DNA damage, necrosis, cell apoptosis, and chromosome breakage [4, 5]. Despite the advancements in medical and surgical therapies, the osteomyelitis (bone infection) rates after TJR procedures are still noticeable with 0.5–6% for total hip replacement (THR) and about 1.5% in total knee replacement (TKR) [6, 7]. It has been predicted that by the year 2030, there will be a rise of 174% and 673% in THR and TKR procedures, respectively [8]. Therefore, the need for improvements in the performance of the current generation of biomaterials is of prime importance and interest.

ª Materials Research Society 2019

Calcium phosphate–based coating, especially HA (Ca10 (PO4)6(OH)2), plays a crucial role in enhancing the corrosion resistance and biologic response of metallic biomaterials [9, 10]. There are various methods to produce HA coating on a metallic substrate, among which plasma spray technique is commercially well proven and approved b